Selective blockade of substance P or neurokinin A receptors reduces the expression of c-fos in trigeminal subnucleus caudalis after corneal stimulation in the rat

Stimulation of the cornea activates neurons in two distinct regions of the spinal trigeminal nucleus: at the transition between trigeminal subnucleus interpolaris and subnucleus caudalis and at the transition between trigeminal subnucleus caudalis and the upper cervical spinal cord as estimated by expression of the immediate early gene, c-fos. To determine if receptors for substance P or neurokinin A, neurokinin 1 and neurokinin 2 receptors, respectively, contribute to the production of Fos-positive neurons in these brainstem regions, receptor-selective antagonists were given intracerebroventricularly 15 min prior to stimulation of the cornea in anesthetized rats. The number of Fos-positive neurons produced in superficial laminae at the trigeminal subnucleus caudalis/cervical cord transition by application of the selective small fiber excitant, mustard oil, to the corneal surface was reduced by the neurokinin 1 receptor antagonist, CP99,994 (5-100 nmol, i.c.v.) and the neurokinin 2 receptor antagonist, MEN10,376 (0.01-1.0 nmol, i.c.v.). Combined pretreatment with CP99,994 and the competitive N-methyl-D-aspartate receptor antagonist, CPP, caused a greater reduction in c-fos expression at the subnucleus caudalis/cervical cord transition than after either drug alone suggesting interaction between receptors for glutamate and substance P. Tachykinin receptor antagonists did not reduce the number of Fos-positive neurons produced at the subnucleus interpolaris/subnucleus caudalis transition. The elevation in plasma concentration of adrenocorticotropin, but not the increases in arterial pressure or heart rate, evoked by corneal stimulation was prevented by pretreatment with CP99,994 or MEN10,376 at doses lower than those needed to reduce c-fos expression. The results indicate that receptors for substance P and neurokinin A contribute to the transmission of sensory input from corneal nociceptors to brainstem neurons in trigeminal subnucleus caudalis and to increased activity of the hypothalamo-pituitary axis that accompanies acute stimulation of the cornea.     

Peptide-containing neurons remain unaffected after intestinal autotransplantation: an experimental study in the piglet

The gut is richly supplied with peptide-containing nervous elements. In the present immunocytochemical study the origin, occurrence and topographical distribution of nerves containing vasoactive intestinal polypeptide (VIP), enkephalin, substance P (SP), somatostatin, neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), gastrin-releasing peptide (GRP) and galanin were investigated in the porcine small intestine. In order to study the origin (extrinsic or intrinsic) of the nerve fibers, specimens from autotransplanted and extrinsically denervated jejunum were examined. Furthermore, possible changes in the distribution of intrinsic neurons after extrinsic denervation were studied. In the control jejunum each nerve fiber population had its own characteristic topographic distribution. There was no overt difference in distribution pattern of peptide-containing nerve fibers and cell bodies between the transplanted and the control segment except that NPY-, SP- and CGRP-containing nerve fibers disappeared around blood vessels. Thus VIP-, somatostatin-, GRP-, enkephalin- and galanin-containing nerve fibers were visibly unchanged in the transplanted segment. The results support the view that the peptide-containing nerve fibers are mainly intrinsic in origin except the NPY-, SP- or CGRP-containing perivascular nerve fibers which are extrinsic to the gut wall. In addition, the results of the present study suggest that transplantation and extrinsic denervation have no major effect on the distribution pattern of the intrinsic neuronal systems.     

A confocal microscopic survey of serotoninergic axons in the lumbar spinal cord of the rat: co-localization with glutamate decarboxylase and neuropeptides

Patterns of co-localization of serotonin with glutamate decarboxylase (the synthetic enzyme for GABA) or each one of eight neuropeptides (calcitonin gene-related peptide, dynorphin, enkephalin, galanin, neuropeptide Y, neurotensin, substance P and somatostatin) were investigated with dual-colour confocal laser scanning microscopy in the lumbar spinal cords of three adult rats. Four regions of the gray matter were studied (laminae I-II, V, IX and X). The extent of co-localization was estimated by direct assessment of merged pairs of optical sections and by automated image analysis. Co-localization of serotonin and glutamate decarboxylase was found only in a few axons of laminae I-II but was not detected in other laminae. Peptides were not co-localized with serotonin in the superficial dorsal horn but considerable co-localization was found in motor nuclei and sparse co-localization was found in laminae V and X. Galanin and substance P frequently co-existed with serotonin in lamina IX but some co-localization with dynorphin, somatostatin, [Met]enkephalin and neuropeptide Y was also detected. Galanin, substance P and dynorphin were also co-localized with serotonin in a few axons of the deep dorsal horn and in the gray matter around the central canal. Neurotensin and calcitonin gene-related compound did not co-exist with serotonin in any of the laminae investigated. This evidence suggests that different populations of serotoninergic axons project to different regions of the spinal gray matter. Those containing glutamate decarboxylase terminate in the superficial dorsal horn and are likely to be involved in antinociception, whereas those containing peptides terminate principally in motor nuclei and are likely to modulate motor activity.     

Central projection of calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive trigeminal primary neurons in the rat

Substance P (SP) is implicated in transmission of primary afferent nociceptive signals. In primary neurons, SP is colocalized with calcitonin gene-related peptide (CGRP), which is another neuropeptide marker for small to medium primary neurons. CGRP coreleased with SP augments the postsynaptic effect of SP and thereby modulates the nociceptive transmission. This study demonstrates the distribution of CGRP-like immunoreactivity (-ir) and SP-ir in the lower brainstem of normal rats and after trigeminal rhizotomy or tractotomy at the level of subnucleus interpolaris (Vi). By comparing the results obtained from normal and deafferented rats, we analyzed the central projection of trigeminal primary nociceptors. The CGRP-immunoreactive (-ir) trigeminal primaries projected to the entire rostrocaudal extent of the spinal trigeminal nucleus, the principal nucleus (PrV), the paratrigeminal nucleus (paraV), and the lateral subnucleus of solitary tract nucleus (STN) on the ipsilateral side. The trigeminal primaries projecting to the spinal trigeminal nucleus, paraV and STN also contained SP-ir. The ipsilateral trigeminal primaries were the exclusive source of CGRP-ir terminals in the PrV, the Vi and the dorsomedial nucleus within the subnucleus oralis (Vo). The medullary dorsal horn (MDH) and the lateral edge of Vo received convergent CGRP-ir projection from the ipsilateral trigeminal primaries and other neurons. The glossopharyngeal and vagal primaries are candidates for the source of CGRP-ir projection to the Vo and the MDH, while the dorsal root axons supply the MDH with CGRP-ir terminals. In addition, contralateral primary neurons crossing the midline appear to contain CGRP and to terminate in the MDH.     

Distribution and origin of peptide-containing nerve fibres in the rat and human mammary gland

The structures in the mammary gland involved in milk ejection have been investigated with regard to their relation to different types of peptidergic nerve fibres and their origin. Lactating rats were studied with immunohistochemistry focusing on the nipple, the parenchyma, the mammary blood vessels and the mammary nerve. The human mammary gland was also analysed. In the mammary gland from rat and human, nerve endings in the subepidermis, around smooth muscle cells in the nipple, in the connective tissue surrounding lactiferous ducts and alveoli in the nipple and in the parenchyma of the mammary gland showed immunoreactivity for calcitonin gene-related peptide, substance P, vasoactive intestinal polypeptide, peptide histidine isoleucine, neuropeptide Y, galanin and tyrosine hydroxylase, whereas dynorphin-positive nerve fibres could not be detected. The mammary nerve contained calcitonin gene-related peptide, vasoactive intestinal polypeptide, neuropeptide Y and tyrosine hydroxylase immunoreactivities; the adventitia of the mammary artery contained nerve fibres immunoreactive for neuropeptide Y and tyrosine hydroxylase, while vasoactive intestinal polypeptide-, peptide histidine isoleucine-, calcitonin gene-related peptide- and substance P-positive fibres were found in the tissue surrounding the artery. The wall of the mammary vein had nerve terminals immunoreactive for neuropeptide Y, tyrosine hydroxylase, calcitonin gene-related peptide and substance P. With the help of retrograde tracing using wheat germ agglutinin in combination with immunohistochemistry, projections of calcitonin gene-related peptide-immunoreactive cells in the dorsal root ganglia to the nipple were established. Neurons in the sympathetic stellate ganglion containing neuropeptide Y and tyrosine hydroxylase also projected to the mammary gland. Moreover retrogradely-labelled cells were found in the nodose ganglion, and they were vasoactive intestinal polypeptide-immunoreactive. These results demonstrate a rich distribution of different types of nerve fibres in structures of the mammary gland related to milk ejection. These nerve fibres and their peptides may be involved in the local control of milk ejection.     

Attenuation of Fos-like immunoreactivity in the trigeminal nucleus caudalis following trigeminovascular activation in the anaesthetised guinea-pig

The present study has examined the involvement of sensory neurotransmitters in activating neurones in the trigeminal nucleus caudalis following stimulation of the trigeminovascular system in anaesthetised guinea-pigs. Electrical stimulation of the right trigeminal ganglion produced a unilateral expression of Fos-like immunoreactivity (Fos-LI) in the trigeminal nucleus caudalis. The tachykinin NK1 receptor antagonist, GR205171 (100 micrograms/kg i.v.) and the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (1 mg/kg i.v.) each inhibited expression of Fos-LI following electrical stimulation. The calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP8-37 (1.3 mg/kg i.v.), administered following rostral intracarotid infusion of mannitol to disrupt the blood-brain barrier, tended to reduce Fos-LI evoked by electrical stimulation, although this failed to reach statistical significance. Capsaicin (10 nmol in 0.1 ml), administered intracisternally, produced a bilateral expression of Fos-LI in the trigeminal nucleus caudalis. This expression was unaffected by the peripherally acting NK1 receptor antagonist, GR82334 (0.2 mg/kg i.v.) or CGRP8-37 (1.3 mg/kg i.v.). The centrally penetrant NK1 receptor antagonist, GR205171 (100 micrograms/kg i.v.), inhibited significantly Fos-LI evoked by intracisternal capsaicin administration. It is concluded that the sensory neurotransmitters, substance P and glutamate are released centrally following activation of the trigeminovascular system and that each may be involved in activation of cells in the trigeminal nucleus caudalis.     

Neuropeptide immunoreactivity in ligature-induced neuromas of the inferior alveolar nerve in the ferret

Injury to branches of the trigeminal nerve can sometimes result in persistent dysaesthesia. In an attempt to understand the aetiology of this condition we are currently investigating changes which occur at the injury site. In the present study we have examined the expression of seven neuropeptides, all of which have been implicated in nociceptive transmission, or have previously been shown to have altered expression following nerve injury. In 20 adult ferrets the inferior alveolar nerve was sectioned and ligated, and recovery permitted for 3 days, 8 days, 3 weeks, 6 weeks or 12 weeks. Longitudinal sections of the neuromas were processed using immunohistochemical techniques to quantify the expression of substance P, calcitonin gene-related peptide, vasoactive intestinal polypeptide, galanin, somatostatin, enkephalin and neuropeptide Y. After 3 days, all of the neuropeptides were expressed at the injury site. In the neuromas examined after longer recovery periods these levels of expression had declined and were similar to those found in the contralateral controls. This initial high level, followed by a decline, parallels the incidence of ectopic neural activity recorded electrophysiologically in the same model. It is, therefore, possible that the accumulation of neuropeptides at the injury site may play a role in the initiation or modulation of ectopic neural activity.     

Immunologically induced sympathectomy of preganglionic nerves by antibodies against acetylcholinesterase: increased levels of peptides and their messenger RNAs in rat adrenal chromaffin cells

Systemic administration of murine monoclonal acetylcholinesterase antibodies to rats has been shown to cause selective degeneration of sympathetic preganglionic neurons. In the present study rats were subjected to a single i.v. injection of these acetylcholinesterase antibodies, or to normal IgG or saline for control. Exophthalmos, piloerection and eyelid-drooping (ptosis) were observed within 1 h after administration of the antibodies. Rats were killed at different time-points after antibody administration, and the adrenal glands were analysed by means of indirect immunohistochemistry and in situ hybridization histochemistry. As soon as 3 h after the antibody treatment, a marked increase in the number of chromaffin cells expressing mRNA encoding, respectively, enkephalin, calcitonin gene-related peptide, galanin, neurotensin and substance P was seen. At 12 h the peptide mRNA levels were still elevated and there was a concomitant increase in the number of peptide-immunoreactive cells. All peptide levels remained high for at least 48 h; however, 77 days after the antibody treatment only enkephalin-immunoreactive cells could be encountered. A disappearance of acetylcholinesterase- and enkephalin-immunoreactive cells could be encountered. A disappearance of acetylcholinesterase- and enkephalin-positive fibers was already seen 3 h after the antibody treatment, and after 24 h no fibers were encountered. In contrast, up until 48 h there was no apparent change in the number or intensity of immunofluorescent fibers expressing calcitonin gene-related peptide, galanin, neurotensin or substance P. However, 77 days after the antibody treatment the number of calcitonin gene-related peptide- and substance P-immunoreactive fibers was increased as compared to controls. In addition, reappearance of acetylcholinesterase- and enkephalin-immunoreactive fibers was seen 77 days after antibody administration, although their number was still low as compared to controls. Double-labeling immunohistochemistry revealed that the chromaffin cells expressing peptides after the antibody treatment preferentially were adrenaline storing cells (noradrenaline-negative). The majority of these cells expressed only one peptide. Both surgical transection of the splanchnic nerve as well as treatment with acetylcholine receptor antagonists mimicked the effects seen after the acetylcholinesterase-antibody treatment, although changes were less pronounced. The present results show that interruption of splanchnic transmission induces fast, marked, and selective increases in peptide expression in rat adrenal chromaffin cells.     

Nitric oxide in the stress axis

Calcitonin gene-related peptide in sensory primary afferent neurons has an excitatory effect on postsynaptic neurons and potentiates the effect of substance P in the rat spinal dorsal horn. It has been established that calcitonin gene-related peptide expression in dorsal root ganglion neurons is depressed, and the effect of calcitonin gene-related peptide on dorsal horn neurons is attenuated, following peripheral nerve injury. We report here that a subpopulation of injured dorsal root ganglion neurons show increased expression of calcitonin gene-related peptide. Using in situ hybridization and the retrograde tracer, FluoroGold, we detected an increased number of medium- to large-sized rat dorsal root ganglion neurons projecting to the gracile nucleus that expressed alpha-calcitonin gene-related peptide messenger RNA following spinal nerve transection. Immunohistochemistry revealed a significant increase in calcitonin gene-related peptide immunoreactivity in the gracile nucleus and in laminae III-IV of the spinal dorsal horn. These results indicate that a subpopulation of dorsal root ganglion neurons express alpha-calcitonin gene-related peptide messenger RNA in response to peripheral nerve injury, and transport this peptide to the gracile nucleus and to laminae III-IV of the spinal dorsal horn. The increase of the excitatory neuropeptide, calcitonin gene-related peptide, in sites of primary afferent termination may affect the excitability of postsynaptic neurons, and have a role in neuronal plasticity following peripheral nerve injury.     

Synergistic inhibitory effect of angiotensin-converting enzyme inhibitor and heparin on intimal hyperplasia after rat aorta injury

To study the interaction between human recombinant interleukin-1 alpha and the nervous system, substance P-, neurokinin A-, calcitonin gene-related peptide-, and neuropeptide Y-like immunoreactivity in the cerebrospinal fluid, plasma, and temporomandibular joint (TMJ) perfusates of rats during acute experimental monarthritis were examined. The right TMJs of the experimental rats were injected with 0.01 mL of human recombinant interleukin-1 alpha. The right TMJs of control rats were injected with 0.01 mL of saline. Cerebrospinal fluid, plasma, and perfusates from the right TMJs were obtained at 2, 6, and 24 hours following injection, and neuropeptide-like immunoreactivity was analyzed by specific radioimmunoassays. Values of neuropeptide-like immunoreactivity for the experimental rats were compared with those of the control rats. In the experimental group, substance P-, neurokinin A-, and calcitonin gene-related peptide-like immunoreactivities were increased in cerebrospinal fluid compared to those of the control group. In plasma, no changes in neuropeptide-like immunoreactivities rose significantly in the TMJ perfusates. Most pronounced changes in neuropeptide Y-like immunoreactivity occurred intra-articularly in the TMJ perfusates. The results indicate that the contribution of the nervous system to human recombinant interleukin-1 alpha-induced monarthritis is most pronounced in the affected joint.     

Calcitonin gene-related peptide- and substance P-like-immunoreactive innervation of the anterior pituitary in the rat

In our previous studies substantial amounts of substance P- and calcitonin gene-related peptide-like-immunoreactive nerve fibers have been identified in the anterior pituitary of the monkey and the dog. They were found to be in close proximity to the gland cells, even making synaptic contacts with some types of the gland cells. The present study investigated in detail the calcitonin gene-related peptide- and substance P-like immunoreactivities of the anterior pituitary in the rat. Though the immunoreactive fibers were not as abundant as in the anterior pituitary of the monkey and the dog, they still appeared in notable amounts. The calcitonin gene-related peptide- and substance P-like-immunoreactive nerve fibers occurred mostly as thin, tortuous, and densely varicose fibers, weaving among the gland cells. They are widely distributed, more in the central part of the gland. Double-immunostaining proved nearly complete co-localization of these two peptides in the nerve fibers. It is hypothesized that the anterior pituitary can be regulated by direct neural factors as well as humoral factors.     

Release of immunoreactive substance P in the trigeminal brain stem nuclear complex evoked by chemical stimulation of the nasal mucosa and the dura mater encephali--a study with antibody microprobes

In order to study a possible involvement of substance P in the processing of chemonociceptive input from the nasal mucosa and the dura mater encephali in the spinal trigeminal, the release of immunoreactive substance P was measured in the trigeminal brain stem nuclear complex in anaesthetized rats. Microprobes coated with antibody to substance P were inserted into the lateral area of the brain stem up to 1 mm posterior to the obex corresponding to the trigeminal subnucleus caudalis. When the nasal mucosa was stimulated by topical administration of mustard oil (1% and 5%) into the nostrils, immunoreactive substance P was mainly detected in the dorsal region of the trigeminal brain stem nuclear complex with a maximum in the superficial gray matter. When the dura mater encephali was stimulated by topical administration of Tyrode's solution (pH 6.2), immunoreactive substance P was mainly released in the ventral region of the trigeminal brain stem nuclear complex; with pH 5.5 the release was more diffuse extending from the ventral to the dorsal part of the spinal trigeminal nucleus. Release was maximal rather after than during the administration of the stimuli, and it considerably outlasted the stimulation periods. These data suggest that substance P plays an important role in the processing of chemonociceptive inputs from the nasal mucosa and the dura mater encephali in the trigeminal brain stem nuclear complex. Substance P may be important, therefore, in the generation of those headaches that are caused by affections of the nasal mucosa and the dura mater encephali. Since enhanced levels of immunoreactive substance P were present for considerable time periods beyond the administration of the stimuli, substance P and neurokinin-1 receptors may be involved in long-lasting neuronal events following noxious stimulation.     

Trigeminal-reticular connections: possible pathways for nociception-induced cardiovascular reflex responses in the rat

Cardiovascular regulatory neurons of the ventral medulla and pons are thought to have an important role in the mediation of trigeminal nociception-induced reflex cardiovascular responses. However, the neural pathways that link the spinal trigeminal nucleus with ventral medullary and pontine autonomic cell groups are poorly understood. The present study utilized injections of the highly sensitive anterograde tracer substance biotinylated dextran combined with immunocytochemistry for tyrosine hydroxylase, the synthesizing enzyme for catecholamines, to investigate the distribution and morphology of projections from the spinal trigeminal subnucleus caudalis to ventral medullary and pontine catecholaminergic cell groups. Injection of biotylinated dextran into the dorsal subnucleus caudalis produced dense anterograde labeling in dorsal regions of the medullary and pontine reticular formation including the dorsal medullary reticular field, the parvicellular reticular field, and the parvicellular reticular field pars anterior. In the ventral medullary and pontine reticular formation, light anterograde labeling tended to be distributed in close proximity to the distal dendrites of catecholaminergic neurons located in the C1, A1, and A5 regions. Injections of anterograde tracer into the dorsal medullary reticular field produced dense anterograde labeling in the ventral medullary and pontine reticular formation. Numerous terminal-like varicosities were observed in close proximity to catecholaminergic neurons located in the C1, A1, and A5 regions. These data suggest that trigeminal pain-induced reflex cardiovascular responses involve indirect projections that terminate in the dorsal medullary and pontine reticular formation before reaching ventral medullary and pontine catecholaminergic cell groups known to be involved in cardiovascular regulation.     

Apposition of enkephalin- and neurotensin-immunoreactive neurons by serotonin-immunoreactive varicosities in the rat spinal cord

The descending serotonergic system provides a powerful inhibitory input to the dorsal horn of the spinal cord. Little is known about the chemical identity of the spinal neurons that the serotonergic system innervates, although spinal enkephalinergic neurons are likely candidates. This study investigated the apposition of serotonin-immunoreactive varicosities onto enkephalin- and neurotensin-immunoreactive neurons in the rat lumbosacral spinal cord. Using a double immunofluorescence technique, serotonin-immunoreactive varicosities were observed to abut the soma or proximal dendrites of [Met]enkephalin- and neurotensin-immunoreactive neurons. Nearly 75% of all [Met]enkephalin- and neurotensin-immunoreactive neurons were apposed by serotonin-immunoreactive varicosities in the marginal zone and dorsal gray commissure. In substantia gelatinosa, approximately half of the [Met]enkephalin- and neurotensin-immunoreactive neurons were juxtaposed by serotonin-immunoreactive varicosities. [Met]enkephalin-immunoreactive neurons also were bordered by serotonin-immunoreactive varicosities in the nucleus proprius (65%) and sacral parasympathetic nucleus (75%). The results of this study suggest that the descending serotonergic system mediates nociception via probable contacts with intrinsic enkephalin and neurotensin spinal systems. The mode of action of spinal serotonin on enkephalin and neurotensin neurons may be through "volume" transmission vs synaptic or "wiring" transmission.     

An acid sensing ion channel (ASIC) localizes to small primary afferent neurons in rats

The acid sensing ion channel (ASIC) identified in rat brain and spinal cord is potentially involved in the transmission of acid-induced nociception. We have developed polyclonal antisera against ASIC, and used them to screen rat brain and spinal cord using immunocytochemistry. ASIC-immunoreactivity (-ir) is present in but not limited to the superficial dorsal horn, the dorsal root ganglia (DRG) and the spinal trigeminal nucleus, as well as peripheral nerve fibers. These observations, combined with the disappearance of ASIC-ir following dorsal rhizotomy, suggest localization of ASIC to primary afferents. DRG ASIC-ir co-localizes with substance P (SP) and calcitonin gene-related peptide (CGRP)-ir in small capsaicin-sensitive cell bodies, suggesting that ASIC is poised to play a role in the transduction of noxious stimuli.     

Colocalization of substance P or enkephalin in serotonergic neuronal afferents to the hypoglossal nucleus in the rat

The serotonergic innervation of the hypoglossal nucleus originates from the caudal raphe nuclei. Non-serotonergic neurons in the caudal raphe nuclei also project to the hypoglossal nucleus. We employed a triple-fluorescence technique to determine whether the substance P- or the enkephalin-containing neurons in the caudal raphe nuclei that projected to the hypoglossal nucleus also contained serotonin. Rhodamine latex microspheres were injected into the hypoglossal nucleus, and then serotonin and peptide dual-immunofluorescence was performed to colocalize perikarya containing serotonin, substance P, and rhodamine microspheres; or perikarya containing serotonin, enkephalin, and rhodamine microspheres. Our results demonstrate that most substance P-containing neuronal afferents to the hypoglossal nucleus colocalize serotonin. In contrast, few enkephalin-containing neuronal afferents to the hypoglossal nucleus also contain serotonin. These data suggest that substance P projections to the hypoglossal nucleus are a subset of serotonergic projections and that limited overlap exists between the populations of enkephalinergic and serotonergic neuronal afferents to the hypoglossal nucleus. Either substance P- or enkephalin-containing somata account for a very small proportion of non-serotonergic caudal raphe projections to the hypoglossal nucleus. Finally, these data demonstrate the medial tegmental field origins of the substance P projections and the enkephalin projections to the hypoglossal nucleus.     

Tooth pulp neurons in the caudal medulla oblongata of the cat

The medulla oblongata caudal to the obex was explored for neurons responsive to tooth pulp (TP) stimulation in cats. Four different subclasses of TP neurons were found. The latter included TP specific (TPS) neurons, trigeminal wide dynamic range (trigeminal WDR) neurons with TP input, trigeminal subnucleus reticularis ventralis (trigeminal SRV) neurons with TP input and convergent reticular formation (convergent RF) neurons with TP input. TPS neurons were located in the dorsal marginal rim of the trigeminal subnucleus caudalis, i.e., in the marginal layer or the outer zone of substantia gelatinosa. WDR neurons with TP input were found in the neck region of medullary dorsal horn which corresponds to the lateral part of subnucleus reticularis dorsalis (SRD). Trigeminal SRV neurons with TP input were located in the lateral part of SRV. Convergent RF neurons with TP input were found in the middle third of the caudal bulbar RF consisting of SRD and SRV. Both TPS neurons and WDR neurons with TP input included trigeminothalamic neurons as evidenced by the antidromic activation from the nucleus ventralis posteromedialis of the contralateral thalamus. A significant proportion of both trigeminal SRV and convergent RF neurons with TP input were antidromically activated by stimulation of the nucleus centralis lateralis of the contralateral thalamus. The former two subclasses may subserve the sensory-discriminative aspect of toothache, while the latter two subclasses, the emotional-motivational aspect.     

Sympathetic axons surround neuropeptide-negative axotomized sensory neurons

Nerve injury can lead to sympathetically dependent neuropathic pain. A possible site of sympathetic-sensory interaction is the dorsal root ganglion (DRG), where sympathetic axons form pericellular 'baskets' around a subpopulation of DRG neurons. Since these structures possibly represent functional units of sympathetic pain, we attempted to characterize the neuropeptidergic phenotype of basketed DRG neurons. We performed double-labeling immunohistochemistry for tyrosine hydroxylase and neuropeptides on DRG sections, 2 weeks following L5 spinal nerve ligation (a well-characterized animal model of sympathetic pain). We found that basketed DRG neurons typically do not contain substance P, calcitonin gene-related peptide, galanin, neuropeptide tyrosine, or vasoactive intestinal polypeptide, and we conclude that if sympathetic baskets contribute to neuropathic pain, the involvement of these neuropeptides is unimportant.     

Codon bias evolution in Drosophila. Population genetics of mutation-selection drift

Reflex cardiovascular responses elicited by noxious oro-facial stimulation are well known but the neural pathways that underlie trigeminal cardiovascular reflex reactions remain to be elucidated. In previous studies, we have shown that noxious electrical stimulation of the mandibular incisor in the anesthetized rat elicits increases in mean arterial blood pressure and heart rate (Allen, G.V., Barbrick, B. and Esser, M.J., Trigeminal parabrachial connections: possible pathway for nociception-induced cardiovascular reflex responses, Brain Res., 715 (1996) 125-135). In this study, microinjections of the presynaptic blocker, cobalt chloride, or the anesthetic agent, lidocaine, were made into selected brainstem sites to identify neural pathways that are involved in mediation of the reflex pressor responses. Ipsilateral and bilateral injections of chemical blocker into the dorsomedial spinal trigeminal nucleus, pars caudalis, lateral parabrachial nucleus and the rostral ventral lateral medulla/caudal A5 region attenuated the reflex cardiovascular response. Bilateral injections of cobalt chloride into the dorsomedial subnucleus caudalis resulted in 70-100% attenuation of the reflex pressor response. Bilateral injections of cobalt chloride and/or lidocaine into the lateral parabrachial nucleus or the rostral ventral lateral medulla/A5 region resulted in 43-57% and 44-100% attenuation of the reflex pressor response, respectively. There were no significant differences in the degree or duration of attenuation of the reflex pressor responses produced by cobalt chloride compared to that produced by lidocaine injections. The reflex pressor responses usually returned to baseline levels approximately 60 min following injection of the chemical blocker substance. The results indicate that noxious electrical stimulation of the mandibular incisor elicits a reflex increase in mean arterial blood pressure which is initially mediated in the dorsomedial spinal trigeminal nucleus, pars caudalis and is subsequently mediated in the lateral parabrachial nucleus and the rostral ventral lateral medulla/caudal A5 region.     

Abnormalities of neuropeptides and neural markers in the esophagus of fetal rats with adriamycin-induced esophageal atresia

BACKGROUND/PURPOSE: To investigate the distribution of neural markers and neuropeptides in esophageal atresia (EA). METHODS: A fetal rat model with Adriamycin-induced EA was used. The animals were divided into four groups: (1) control group, (2) saline-injected group, (3) Adriamycin administered but without the development of EA, and (4) Adriamycin-induced EA group. Specimens of the distal esophagus from each group were immunostained using antibodies to S100, protein gene product 9.5 (PGP), somatostatin, vasoactive intestine peptide (VIP), bombesin, galanin, substance P, neuropeptide Y (NPY), calcitonin gene-related product (CGRP), met-encephalin, nitric oxide synthase, and tyrosine hydroxylase. RESULTS: The total cross-sectional area of the distal atretic esophagus was significantly smaller than controls (P = .01), the submucosa being the component most affected (0.0465 v 0.0234 mm). Immunoreactivity for S100 and galanin were significantly elevated in the atresia group (0.0288 v 0.0079 and .001 v 0.000). In addition, there was also an increase in CGRP and Substance P in the atretic group. CONCLUSION: The elevated levels of S100 and galanin could explain the disordered motility observed in patients who had esophageal atresia.