Early formation of sexually dimorphic glomeruli in the developing olfactory lobe of the brain of the moth Manduca sexta

The antennal lobes (ALs), the primary olfactory centers, of the moth Manduca sexta are sexually dimorphic. Only ALs of males possess the macroglomerular complex (MGC), the site of primary processing of information about the female's sex pheromone. To understand the development of identified, odor-specific olfactory glomeruli, we investigated the cellular events involved in the morphogenesis of the MGC by means of various fluorescence staining techniques and laser-scanning confocal microscopy. The MGC lies near the entrance of the antennal nerve into the AL of the adult male and comprises three glomeruli, the globular cumulus and two toroidal structures. The MGC forms during early stages of metamorphic adult development through a stereotyped sequence of coordinated changes in MGC-specific receptor axons, glial cells, and early-ingrowing projection neurons of the medial group of AL neurons. The MGC divisions are the earliest glomeruli to form in the male AL, and their basic organization is established within about 3 days after ingrowth of the first sensory axons. Despite their special anatomical features, the MGC glomeruli develop in a manner similar to that of the ordinary glomeruli. Comparison of the ALs of males and females reveals that two relatively large and early-developing glomeruli that are situated dorsolaterally in the female AL appear to be female-specific. Development of the sexually dimorphic glomeruli diverges immediately after the ingrowth of the first olfactory receptor axons, resulting in the formation of these large glomeruli in females and the MGC in males.     

Evidence for the involvement of the nitric oxide-cGMP pathway in the antinociception of morphine in the formalin test

The effect of inhibition of nitric oxide synthesis and guanylate cyclase on the peripheral antinociceptive effect of morphine was assessed by using the formalin test in the rat. Saline, N(G)-monomethyl-L-arginine, a nitric oxide synthesis inhibitor (50 microg) and methylene blue, a guanylate cyclase inhibitor (500 microg), did not exhibit any antinociceptive activity. However, morphine (10 microg) produced a significant antinociceptive effect in phases 2a and 2b, which was reduced by pretreatment with either N(G)-monomethyl-L-arginine or methylene blue. These results suggest that the local administration of morphine induces antinociception by the activation of the L-arginine-nitric oxide-cGMP pathway.     

Programmed cell death of identified peptidergic neurons involved in ecdysis behavior in the Moth, Manduca sexta

Molecular dynamics simulation in explicit solvent and continuum solvent models are applied to investigate the relative stability of A- and B-form helices for two DNA sequences, dA10-dT10 and dG10-dC10 in three structural forms. One structural form is based on an unrestrained molecular dynamics (MD) trajectory starting from a canonical B-DNA structure, the second is based on a MD trajectory starting in a canonical B-DNA structure with the sugars constrained to be C2'-endo and the third simulation started from a canonical A-DNA structure with the sugars constrained to C3'-endo puckers. For the energetic analysis, structures were taken as snapshots from nanosecond length molecular dynamics simulations computed in a consistent fashion in explicit solvent, applying the particle mesh Ewald method and the Cornell et al. force field. The electrostatic contributions to solvation free energies are computed using both a finite-difference Poisson-Boltzmann model and a pairwise Generalized Born model. The non-electrostatic contributions to the solvation free energies are estimated with a solvent accessible surface area dependent term. To estimate the gas phase component of the relative free energy between the various structures, the mean solute internal energies (determined with the Cornell et al. molecular mechanics potential including all pairwise interactions within the solute) and estimates of the solute entropy (using a harmonic approximation) were used. Consistent with experiment, the polyG-polyC (GC) structures are found to be much more A-phillic than the polyA-polyT (AT) structures, the latter being quite A-phobic. The dominant energy components responsible for this difference comes from the internal and van der Waal energies. A perhaps less appreciated difference between the GC and AT rich sequences is suggested by the calculated salt dependence which demonstrates a significantly enhanced ability to drive GC rich sequences towards an A-form structure compared to AT rich sequences. In addition to being A-phobic, the AT structure also has a noticably larger helical repeat than GC and other mixed sequence duplexes, consistent with experiment. Analysis of the average solvent density from the trajectories shows hydration patterns in qualitative agreement with experiment and previous theoretical treatments.     

An olfactory sensory map develops in the absence of normal projection neurons or GABAergic interneurons

Olfactory sensory neurons expressing a given odorant receptor project to two topographically fixed glomeruli in the olfactory bulb. We have examined the contribution of different cell types in the olfactory bulb to the establishment of this topographic map. Mice with a homozygous deficiency in Tbr-1 lack most projection neurons, whereas mice with a homozygous deficiency in Dlx-1 and Dlx-2 lack most GABAergic interneurons. Mice bearing a P2-IRES-tau-lacZ allele and deficient in either Tbr-1 or Dlx-1/Dlx-2 reveal the convergence of axons to one medial and one lateral site at positions analogous to those observed in wild-type mice. These observations suggest that the establishment of a topographic map is not dependent upon cues provided by, or synapse formation with, the major neuronal cell types in the olfactory bulb.     

Allatostatin-like-immunoreactive neurons of the tobacco hornworm, Manduca sexta, and isolation and identification of a new neuropeptide related to cockroach allatostatins

The YXFGLamide C-terminus serves to define most members of a family of structurally related neuropeptides, the YXFGLamides. These peptides have been identified from the nervous system of various insects and include the allatostatins of cockroaches and crickets, the schistostatins of locusts, and the callatostatins of blowflies. The YXFGLamides have been shown to have various functions, including inhibition of juvenile hormone biosynthesis in cockroaches and crickets and inhibition of contraction of certain insect visceral muscles. We wanted to know if these peptides occur in Manduca sexta and what functions they might have. A new peptide, AKSYNFGLamide, was isolated and identified from M. sexta and has been named "lepidostatin-1"; this is the first YXFGLamide to be found in a lepidopteran, and there are indications that additional YXFGLamides occur in M. sexta. An antiserum to cockroach allatostatins (YXFGLamides) was shown to recognize lepidostatin-1 of M. sexta and was used to map YXFGLamide-immunoreactive neurons in larvae. Because immunoreactive interneurons were found to form an extensive neuropil, YXFGLamides probably function as neuromodulators in M. sexta. Neuroendocrine cells in the brain, abdominal ganglia, and their respective neurohemal organs were YXFGLamide immunoreactive and appear to release YXFGLamides as neurohormones. Immunoreactivity to YXFGLamides and M. sexta diuretic hormone were found to be colocalized and appear to be coreleased in these neuroendocrine cells, indicating that YXFGLamides may be involved in regulation of fluid transport. Innervation of the corpora allata by YXFGLamide-immunoreactive processes was very sparse, suggesting that this innervation does not play an important role in allatostasis. Many thoracic motor neurons were YXFGLamide immunoreactive, suggesting that YXFGLamides may have a myomodulatory or myotrophic function in larvae. However, this immunoreactivity disappeared early in metamorphosis and did not reappear in the adult. The YXFGLamide-immunoreactive neurons in the terminal abdominal ganglion were found to innervate the hindgut, indicating that YXFGLamides may be involved in the control of the rate of myogenic contractions of the larval hindgut.     

Development and organization of a nitric-oxide-sensitive peripheral neural plexus in larvae of the moth, Manduca sexta

Each hemisegment of the Manduca sexta larva is supplied with a subepidermal plexus of approximately 350 multidendritic neurons. An initial set of neurons, the primary plexus neurons, arise at 35-45% of embryogenesis. These neurons comprise 12-16 uniquely identifiable neurons per hemisegment that have homologues in other insect larvae. Each spreads processes across a characteristic portion of the body wall and has an axon that projects into the central nervous system. Secondary plexus neurons are born in two waves: the first between 70% and 80% of embryogenesis and the second during the molt to the second larval stage. The secondary plexus neurons are multidendritic, spread uniformly across the body wall, and appear to make contacts with the primary plexus neurons. Each secondary plexus cell arises as part of a five-cell cluster; the other cells produce a sensory bristle and socket along with the bristle sensory neuron and a glial cell. Application of nitric oxide (NO) donors induces plexus neurons to produce cyclic 3',5' guanosine monophosphate (cGMP), suggesting the presence of soluble guanylate cyclase. With few exceptions, plexus neurons become sensitive to NO stimulation approximately 10 hours after their birth and remain so throughout larval life. Cyclic GMP is detected primarily in the cytoplasm of plexus neurons and extends into the finest peripheral dendrites. Our results suggest that cGMP participates in the development and/or physiology of this peripheral neural plexus.     

The distribution fields of sensory neurons in the human thalamus

Thalamic neurons were identified by activity related to passive joint movement, active joint movement, tapping stimulation, and light touch stimulation during surgery to treat movement disorders. The neurons were classified into three types: movement-related neurons, tapping-related neurons, or superficial sensory neurons. Tapping-related neurons had characteristics of lemniscal sensory neurons and occupied the border area of movement-related neurons and superficial sensory neurons. Tapping-related neurons showed a laminar distribution 1.0-1.5 mm in width in the anterodorsal region of the nucleus ventrocaudalis. Results suggest that the distribution pattern of tapping-related neurons in the human thalamus is consistent with the functional distribution pattern found in the monkey thalamus.     

Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech

In leech, the central annulus of each midbody segment possesses seven pairs of sensilla, which are mixed clusters of primary peripheral sensory neurons that extend their axons into the CNS where they segregate into distinct fascicles. Pathway selection by individual afferent growth cones of sensillar neurons was examined by double labeling using intracellular dye-filling with antibody labeling in early Hirudo medicinalis embryos. The monoclonal antibody Lan3-2 was used because sensillar neuronal tracts are specifically labeled by this antibody. Examining 68 individually filled neurons we found that sensillar neuron growth cones bifurcate within the CNS, that they project long filopodia capable of sampling the local environment, and that all of them appeared to choose a single particular CNS fascicle without apparent retraction or realignment of growth cones. Furthermore, each side of the bifurcating afferent growth cones always chose the same fascicle, implying a specific choice of a distinct labeled pathway. By dye-filling individual central neurons (P-cells), we show that there are centrally projecting axons present at the time sensillar afferents enter the ganglionic primordia and select a particular fascicle, and we confirm that at least the dorsal peripheral nerve is likely to be pioneered by central neurons, not by the peripheral afferents. In the sensillum studied here, we found examples of sensory neurons extending axons into one of all the available fascicles. Thus, an individual embryonic sensillum possesses a heterogeneous population of afferents with respect to the central fascicle chosen. This is consistent with the idea that segregation into distinct axon fascicles may be based upon functional differences between individual afferent neurons. Our findings argue strongly in favor of specific pathway selection by afferents in this system and are consistent with previous suggestions that there exists a hierarchy of cues, including surface glycoconjugates that mediate navigation of the sensillar growth cones and the fasciculation of their axons.     

The organization and postnatal development of the commissural projection of the rat somatic sensory cortex

Anterograde and retrograde tracing experiments have been used to demonstrate the origin and terminal distribution of commissural fibers in the first somatosensory cortex (SI) of the rat. The commissural fibers originate from pyramidal cells of all layers, but predominantly from layers III and V. The fibers terminate in a series of approximately vertical bands. In each of these there are concentrations of terminals extending from the inner portion of the molecular layer to the deep portion of layer III as well as in the superficial part of layer V, and in layer VI. Discrete vertical bands of cortex are reciprocally connected across the midline to give both the origin and terminal regions of the projection a patchy or "columnar" appearance. The commissural fibers arise from and terminate in areas of the cortex that lie between and alongside the aggregations of granule cells that distinguish SI of the rat. No commissural fibers terminate within the aggregations of layer IV cells themselves but the more superficial terminal ramifications may come to overlie these aggregations. A heterotopic projection to the contralateral second somatosensory cortex has been observed and is similar in form to the homotopic projection to SI. Many commissural fibers have crossed the midline in the corpus callosum by the day of birth but lie in the underlying white matter and do not enter the cortical plate until at least the third postnatal day. During the first postnatal week these fibers grow somewhat diffusely into the maturing cortex and their topographic and laminar pattern of distribution attains its adult characteristics by the end of the first week. Commissural axons, thus, arise from immature cells but the maturation of cell form seems to precede the ingrowth of these axons and the acquisition of commissural synapses.     

Developmental and regional-specific expression of FLRFamide peptides in the tobacco hornworm, Manduca sexta, suggests functions at ecdysis

The developmental profile of a family of three FLRFamide (Phe-Leu-Arg-Phe-NH2) peptides in the tobacco hornworm, Manduca sexta, revealed regional-specific expression patterns within the segmental ganglia. Levels of the three peptides-F7G (GNSFLRF-amide), F7D (DPSFLRFamide), and F10 (pEDVVHS-FLRFamide)-were always higher in the thoracic than abdominal ganglia. The predominant peptide also differed regionally, with F7G being highest in the thoracic ganglia and F7G and F100 being equivalent in the abdominal ganglia. Furthermore, we found regional-specific transient declines in ganglion peptide levels temporally correlated to ecdysis. Thoracic ganglion peptide levels declined at each molt, while abdominal ganglion levels declined over a period of 2 days after ecdysis. The decline in central levels was accompanied by an increase in levels in peripheral neurohemal sites, the transverse nerves (TNs). These observations suggest peptides were released from neurosecretory cells (NSCs) at ecdysis. Distinct sets of thoracic and abdominal NSCs and their processes in peripheral neurohemal sites were immunoreactive, supporting the biochemical data. These results also suggest the regional differences may arise from cellular-specific expression patterns for this family of peptides. In addition, fine immunoreactive processes were observed traveling between TNs and skeletal muscles, suggestive of myotropic actions. We propose that the release of different M. sexta FLRFamides from regionally distinct NSCs leads to a coordinated modulation of skeletal and visceral muscles that facilitate ecdysis.     

The effects of NGF and sensory nerve stimulation on collateral sprouting and gene expression in adult sensory neurons

Cerebroside sulfate activator protein (CSAct or saposin B) is one of a group of heat stable, low-molecular-weight proteins that appear to share a common structural motif. These have been referred to as saposin-like proteins and are thought to share a multiple amphipathic helical barrel structure with a conserved pattern of disulfide linkages. Porcine kidney CSAct was prepared in high purity and consisted of three major glycosylated subforms. The protein was studied by physical-chemical methods and evaluated by various methods for structural prediction. All suggest that CSAct has high amounts of alpha-helical conformation and little if any beta-sheet. Circular dichroism (CD) studies indicate 45-50% helical conformation depending on buffer and temperature. There was only a moderate loss in helical content with increasing temperature and no indication of thermal denaturation. Fourier transform infrared spectroscopy (FTIR) measurements on deuterium hydrated self-films also indicated a predominantly helical structure. Helical axis orientation was investigated by both oriented CD and FTIR dichroism, which suggested that the helical axes were roughly parallel and oriented along the axis of the surface on which the self-films had been deposited. One-dimensional nuclear magnetic resonance spectra showed large chemical shift dispersion, indicating a defined tertiary structure with little variation between 6 and 85 degrees C. NOESY spectra failed to show the strong NOE cross peaks expected for a highly helical conformation. This may indicate short-term conformational flexibility within the helices or molecular aggregation at the high protein concentrations employed. These observations are consistent with the 3-4-helix bundle motif suggested for saposin-like proteins by various predictive algorithms.     

Postembryonic neurogenesis in the central nervous system of the tobacco hornworm, Manduca sexta. III. Spatial and temporal patterns of proliferation

Postembryonic neurogenesis leads to a dramatic increase in the number of functional neurons within the segmental ganglia of the moth, Manduca sexta. These adult-specific neurons are generated during larval life by segment-specific arrays of individually identifiable stem cells, or neuroblasts (Nbs). By the end of the feeding larval stage, each Nb has generated a discrete nest of progeny, which ranges in size from less than 10 to more than 70 progeny. The sizes of these identifiable nests of progeny vary in a segment-specific manner, with the thoracic nests containing a greater number of progeny compared with their homologues in the simpler abdominal ganglia. In order to describe those factors that influence the size of the post-embryonic neuronal lineages, we examined the spatial and temporal pattern of postembryonic neurogenesis in the segmental ganglia of Manduca. The rates at which the identifiable nests accumulated progeny were estimated by counting the number of progeny within the nests, using sectioned material isolated from animals at stages ranging from embryonic hatching until the end of the feeding larval stage. All of the postembryonic Nbs began to generate progeny at around the time of the molt to the third larval instar. Each nest added progeny at a rate that was a characteristic of its identity and segment of origin. Although all of the nests within the thorax continued to accumulate progeny throughout the feeding larval stage, several of the abdominal nests showed little or no growth following the molt to the fifth larval instar. The thymidine analog 5-bromo 2-deoxyuridine (5-BrdU) was used to estimate the mitotic rates of the identifiable Nbs. The number of labeled progeny within a nest 24 h after application of 5-BrdU ranged from a low of 1 to 2 to a high of 11 to 13 labeled cells. In some instances there was a good correlation between the estimated mitotic rate of an identified Nb and the rate of growth of its associated nest of progeny. However, several of the identifiable nests accumulated progeny at a slower rate than predicted based on the estimated mitotic rate of the Nb. Cell death appears to be responsible for slowing the growth of the nests during the feeding larval stage. We estimate that 10% to 70% of the neurons generated during the feeding larval stage degenerate within 24 h of their birth. The level of cell death observed within a nest was dependent on both its identity and its segment of origin.     

The use of decapitated insects to study lipid mobilization in adult Manduca sexta: effects of adipokinetic hormone and trehalose on fat body lipase activity

In order to perform studies on lipid mobilization in adult M. sexta, it is necessary to overcome the effects of starvation and handling, which both provoke an increase in hemolymph lipid concentration. When trehalose was injected into intact insects, a 35% decrease in the content of the diacylglycerol (DG)-rich hemolymph lipoprotein, low density lipophorin (LDLp) was observed within 30 min, but the level of LDLp returned to control values after 1 h. Decapitated insects exhibited 60% reduction in LDLp concentration and the levels remained low for at least 24 h. In contrast to intact insects, injection of trehalose into decapitated animals did not alter the LDLp concentration. After decapitation, the response to adipokinetic hormone (AKH) and the ability of the fat body to release DG into the hemolymph was maintained for at least 24 h. In decapitated insects, 6 pmol of AKH-stimulated measurable lipid mobilization and a near maximum response was obtained with 100 pmol of the hormone. The action of trehalose and AKH on the fat body triacylglycerol (TG)-lipase activity in decapitated animals was studied. Fat body homogenates from trehalose-treated insects exhibited a TG-lipase activity 40% lower than the control insects. Activation of fat body triacylglycerol-lipase was observed after injection of AKH, with the extent of activation ranging between 97 and 380% ten min after AKH injection. A time course study showed that the activation of the fat body triacylglycerol lipase preceded the increase in hemolymph LDLp concentration, suggesting that activation of the lipase initiates lipid mobilization. It is concluded that decapitated insects injected with trehalose is a very useful system for investigating the hormonal regulation of lipid mobilization in adult M. sexta.     

Passover eliminates gap junctional communication between neurons of the giant fiber system in Drosophila. off

The Passover-related gene family plays significant roles in cellular connectivity. Mutations in three family members from Drosophila and from Caenorhabditis elegans alter a few specific electrical synapses. The passage of cobalt between Drosophila neurons was used to assay the presence of gap junctional connections. The giant fiber in the wild type has specific gap junctional connections in the brain and in the thorax. In flies mutant for Passover, cobalt cannot pass into or out of the giant fiber in either the anterograde or the retrograde directions. A large number of other gap junctional connections remain unaffected. This demonstrates that the Passover gene is necessary for gap-junctional communication between the neurons of the Drosophila giant fiber system.     

Coexistence of calcium-binding proteins in vagal and glossopharyngeal sensory neurons of the rat

The presence and coexistence of the calcium-binding proteins (CaBPs), calbindin D-28k, parvalbumin and S100 protein, were immunohistochemically examined in the glossopharyngeal and vagal sensory ganglia, the carotid body and taste buds. The CaBPs were found in each ganglion with the nodose ganglion containing the largest number of CaBP-immunoreactive (ir) cells (calbindin D-28k > or = S100 > parvalbumin). The coexistence of CaBPs was found in neurons of the nodose, petrosal, and jugular ganglia. Calbindin D-28k-ir neurons in the nodose and petrosal ganglia frequently colocalized S100-ir whereas calbindin D-28k-ir neurons in the jugular ganglion less frequently contained S100-ir. Only small percentages of calbindin D-28k-ir neurons in each ganglion colocalized parvalbumin. Similarly, S100-ir neurons in the nodose and petrosal ganglia frequently colocalized calbindin D-28k-ir whereas S100-ir neurons in the jugular ganglion less frequently contained calbindin D-28k-ir. Moderate to small percentages of S100-ir neurons in each ganglion colocalized parvalbumin. Parvalbumin-ir neurons nearly always colocalized S100-ir in the nodose, petrosal and jugular ganglia. Moderate to small percentages of parvalbumin-ir neurons in each ganglion colocalized calbindin D-28k. Whereas calbindin D-28k- and S100-ir were colocalized in nerve fibers and cells within taste buds of circumvallate papilla of the tongue, the coexistence of these CaBPs could not be determined in the carotid body. These findings suggest a co-operative role for CaBPs in the functions of subpopulations of nodose and petrosal ganglia neurons.     

Impairment of olfactory discrimination by blockade of GABA and nitric oxide activity in the honey bee antennal lobes.

Honey bees readily associate an odor with sucrose reinforcement, and the response generalizes to other odors as a function of structural similarity to the conditioned odor. Recent studies have shown that a portion of odor memory is consolidated in the antennal lobes (AL), where first-order synaptic processing of sensory information takes place. The AL and/or the sensory afferents that project into them show staining patterns for the enzyme nitric oxide synthase, which catalyzes the release of the gaseous transmitter nitric oxide (NO). The results show that pharmacological blockade of NO release impairs olfactory discrimination only when release is blocked before conditioning. Blockade of GABAergic transmission disrupts discrimination of similar but not dissimilar odorants, and does so when the block occurs before condition or before testing. These results show that GABA and NO regulate the specificity of associative olfactory memory in the AL. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intracortical arborizations and receptive fields of identified ventrobasal thalamocortical afferents to the primary somatic sensory cortex in the cat

The intracortical arborizations of neurons from the ventroposterolateral thalamic nucleus (VPL) in the cat were studied by intraaxonal injections of horseradish peroxidase (HRP) following identification of their receptive fields. In the primary somatic sensory cortex (SI) VPL cells terminated in different cytoarchitectonic areas according to their receptive field modality. Fibers excited by deep tissue or joint rotation arborized preferentially in area 3a. Those responding tonically to cutaneous stimuli were located in the anterior part of area 3b; hairdriven cells terminated in area 3b and in the rostral pole of area 1. All fibers had a similar laminar distribution within SI. Axons terminated mostly in layers VI, iV, and the lower part of layer III. None terminated in layers I and II. Most terminal arbors were oriented along the mediolateral axis of the brain. The main arborization of a single VPL cell formed a bush of about 500 micrometers in diameter. some fibers generated two such bushes with an uninvaded region of about 300 micrometer between them. It is proposed that this patchy organization underlies in part the columnar organization of areas SI. Many VPL cells had secondary projection sites in SI. These were issued from smaller-sized collaterals and were located in a different cytoarchitectonic area than that of the main terminal plexuses. A significant number of these collaterals projected to area 4, Insufficient filling of the collaterals by HRP prevented a more complete characterization of the secondary arbors.     

Comparison of projection neurons in the pontine nuclei and the nucleus reticularis tegmenti pontis of the rat

Dendritic features of identified projection neurons in two precerebellar nuclei, the pontine nuclei (PN) and the nucleus reticularis tegmenti pontis (NRTP) were established by using a combination of retrograde tracing (injection of fluorogold or rhodamine labelled latex micro-spheres into the cerebellum) with subsequent intracellular filling (lucifer yellow) in fixed slices of pontine brainstem. A multivariate analysis revealed that parameters selected to characterize the dendritic tree such as size of dendritic field, number of branching points, and length of terminal dendrites did not deviate significantly between different regions of the PN and the NRTP. On the other hand, projection neurons in ventral regions of the PN were characterized by an irregular coverage of their distal dendrites by appendages while those in the dorsal PN and the NRTP were virtually devoid of them. The NRTP, dorsal, and medial PN tended to display larger somata and more primary dendrites than ventral regions of the PN. These differences, however, do not allow the differentiation of projection neurons within the PN from those in the NRTP. They rather reflect a dorso-ventral gradient ignoring the border between the nuclei. Accordingly, a cluster analysis did not differentiate distinct types of projection neurons within the total sample. In both nuclei, multiple linear regression analysis revealed that the size of dendritic fields was strongly correlated with the length of terminal dendrites while it did not depend on other parameters of the dendritic field. Thus, larger dendritic fields seem not to be accompanied by a higher complexity but rather may be used to extend the reach of a projection neuron within the arrangement of afferent terminals. We suggest that these similarities within dendritic properties in PN and NRTP projection neurons reflect similar processing of afferent information in both precerebellar nuclei.     

The kinetics of sodium channel inactivation in the sensory neurons depends on the type of hydrogen ion buffer

The kinetics of inactivation of TTX-sensitive and TTX-resistant sodium channels in the excitable membrane of rat dorsal root ganglion cells were studied using whole-cell recording technique with the presence of two different pH buffers, Tris and Hepes. It is shown that Tris ions irreversibly interact with inactivation system, accelerating the decaying phase of sodium current. The buffer regulates the gating machinery of two types of the channels. It makes the second order properties more pronounced. On the contrary, the characteristics of inactivation process in Hepes are more close to that we register immediately after the rupture of the cell membrane. We suppose that Hepes buffer is more adequate for investigation of sodium channel inactivation processes.