Early development and organization of the retinopetal system in the larval sea lamprey, Petromyzon marinus L. An HRP study

Bereavement is a major risk factor for physical illness, grief, depression, and anxiety. In contrast to recent tendencies in the psychiatric literature to equate grief and depression, we propose that a careful discrimination between the two must be made for diagnostic, therapeutic, and investigative purposes. We report the results of a longitudinal study of a frequent but neglected event, miscarriage early in pregnancy, to make this point. Clinical criteria for differentiating grief and depressive reactions were developed based on phenomenological criteria and theoretical considerations. We hypothesized that the detrimental psychological and physical consequences occur only when the miscarriage was not mourned and resulted in a depressive reaction, but not in a grief reaction. In a controlled, representative study, 125 consecutive women were assessed shortly after their miscarriage (before the 20th week of gestation) and 6 months (N = 94) and 12 months (N = 90) later. Assessments included standardized questionnaires for life events, depression, physical complaints, anxiety, and a specific, multidimensional grief scale (Munich Grief Scale) that we had developed previously. Immediately after the miscarriage, the average anxiety and depression scores were elevated when compared with 80 pregnant and 125 age-matched community controls. Twenty percent of the patients who had miscarried showed a grief reaction, 12% showed a depressive reaction, and 20% responded with a combined depressive and grief reaction. The remaining women (48%) reported no changes in their emotional reactions. As predicted, longer-lasting psychological, social, and health status changes followed the initial depressive, but not the grief reactions. Depressive reactions were predicted by a history of previous depression, a lack of social resources, and an ambivalent attitude to the lost fetus. The grief measures were reliable and made it possible to discriminate between grief and depression.     

Olfactory and nonolfactory projections in the river lamprey (Lampetra fluviatilis) telencephalon

The projections of the olfactory bulb, the primordial dorsal, piriform and hippocampal pallia, and of the dorsal thalamus were studied in the lamprey Lampetra fluviatilis using horseradish peroxidase (HRP) and HRP coupled to the wheat germ agglutinin (WGA-HRP). There was obtained an experimental morphological evidence of the presence of the direct thalamo-telencephalic projections in this vertebrate species. The anterior and posterior parts of the dorsal thalamic nucleus, the nucleus of Bellonci, the primordial geniculate bodies, the rostral part of the midbrain were identified as the sources of the telencephalic afferents. These connections may serve as a morphological substrate for transmission of nonolfactory impulses to the telencephalon of the lamprey. The projections of the nucleus of Bellonci into the primordial hippocamp were compared to the limbic thalamo-hippocampal pathways of other vertebrates. We have established, that the fibers ascending from the dorsal thalamus were distributed in the same areas, as those descending from the olfactory bulb. These are: mainly the primordial hippocamp and only a few fibers reach the dorsal and piriform pallia, as well as an area free of olfactory projections--the dorsal part of the subhippocampal lobe. We have also demonstrated that, the secondary olfactory fibers mainly projected ipsilaterally to the primordial dorsal and piriform pallia. A lesser dense bulbar projection has been observed ipsilaterally in the primordial hippocamp and in the ventral part of the subhippocampal lobe. Only few olfactory projections were found in the pallial areas and in the subhippocampal lobe contralaterally. The olfactory fiber terminals were also observed ipsilaterally in the septum, striatum, preoptic area and in the contralateral olfactory bulb. Bilateral bulbofugal projections also occur in the diencephalon, namely in the ventral thalamus and in the hypothalamus. Caudally, the secondary olfactory fibers can be traced up to the area of the posterior tuberculum. Afferents to the olfactory bulb in the river lamprey originate in the subhippocampal lobe, in all three pallial formations and probably in the dorsal thalamus. These structures are at the same time the target zones for the olfactory bulb efferent projections, thus being connected reciprocally with the olfactory bulb.     

Role of excitatory amino acids in brainstem activation of spinal locomotor networks in larval lamprey

An in vitro brain/spinal cord preparation from larval lamprey was used to determine the role of excitatory amino acid (EAA) receptors in the descending activation of spinal locomotor networks. The general EAA receptor blockers KYN, PDA, and DGG completely blocked locomotor activity initiated from the brainstem. The NMDA receptor blocker APV and the non-NMDA receptor blocker DNQX usually attenuated but did not block locomotor activity. Relatively long and short cycle times were attenuated about equally by APV or DNQX, and therefore the attenuation was not cycle time dependent. Receptor blockers for EAAs attenuated locomotor activity, but often with little or no change in the cycle time of burst activity. Although both NMDA and non-NMDA receptors for EAAs are important for the descending initiation of locomotor activity in the lamprey, it is unclear whether these receptors are concentrated in areas of the spinal locomotor networks that control cycle time.     

The anterior pretectal nucleus: a proposed role in sensory processing

Four nuclei of the pretectal complex, the olivary pretectal nucleus, the medial pretectal nucleus, the nucleus of the optic tract and the posterior pretectal nucleus, all have a demonstrated role in visual function. In contrast, the anterior pretectal nucleus (APtN) has no inputs from retina and has few outputs to visual accessory nuclei. The APtN has connections with areas associated with sensory functions and it has been suggested that this nucleus may have a role to play in somatosensory processing. An increasing number of behavioural and electrophysiological studies support this view. Brief low-intensity electrical or chemical stimulation of the APtN causes antinociception in the tail flick test in both unanaesthetised and anaesthetised animals. This inhibition of the tail flick response is attenuated by naloxone, alpha-adrenoceptor antagonists and muscarinic cholinergic receptor antagonists. Electrical stimulation of the APtN is similarly effective in the paw pressure and formalin tests. APtN stimulation also causes a brief inhibition of the tooth pulp-evoked jaw opening reflex. studies with [C14]2-deoxyglucose indicate that peripheral noxious stimuli will cause an increase in metabolic activity within the APtN. Animals with electrodes placed in the APtN will self-administer electrical stimulation and this can reduce the aversive and autonomic effects of stimulating the ventromedial hypothalamus. Part of the antinociceptive effects of stimulating the APtN are due to a descending inhibition of spinal dorsal horn projection neurones. Multireceptive neurones deep in the dorsal horn are inhibited by APtN stimulation. In contrast, superficial projection neurones that respond to intense cutaneous stimuli are excited by APtN stimulation. The APtN receives an excitatory input from low-threshold afferents via the dorsal column pathway and a high-threshold excitatory drive from superficial cells projecting through the dorsolateral funiculus. The excitatory input from the dorsal columns may well participate in the long-term inhibition of spinal projection neurones evoked by dorsal column stimulation. These ascending excitatory pathways may also be important to the long-term activation of descending inhibition from the APtN.     

Vestibular nucleus projections to nucleus tractus solitarius and the dorsal motor nucleus of the vagus nerve: potential substrates for vestibulo-autonomic interactions

Autonomic effects of vestibular stimulation are important components of phenomena as diverse as acute vestibular dysfunction and motion sickness. However, the organization of neural circuits mediating these responses is poorly understood. This study presents evidence for direct vestibular nucleus projections to brain stem regions that mediate autonomic function. One group of albino rabbits received injections of Phaseolus vulgaris leucoagglutinin into the vestibular nuclei. The tracer was visualized immunocytochemically with standard techniques. Anterogradely labeled axons from the caudal medial vestibular nucleus (cMVN) and inferior vestibular nucleus (IVN) could be traced bilaterally to nucleus tractus solitarius (NTS). Fewer axons ended near the somata of neurons in the dorsal motor nucleus of the vagus nerve (DMX). A second group of rabbits received pressure or iontophoretic injections of cholera toxin B-HRP or Fluoro-Gold into a region including NTS and DMX. Retrogradely labeled neurons were observed bilaterally in the caudal half of cMVN and ipsilaterally in IVN. The labeled somata were small and they tended to occupy the center of cMVN in transverse sections. These previously unreported vestibular nucleus projections to NTS and DMX are a potential substrate for vestibular influences on autonomic function. In particular, they may contribute to both cardiovascular control during head movements (e.g., orthostatic reflexes) and autonomic manifestions of vestibular dysfunction, motion sickness and exposure to altered gravitational environments.     

Direct retinal projections to GRP neurons in the suprachiasmatic nucleus of the rat

The retinal projections to gastrin-releasing peptide (GRP)-expressing neurons in the rat suprachiasmatic nucleus (SCN) were investigated by double immunofluorescence and immunoelectron microscopy. Optic nerve terminals labeled by cholera toxin B subunit (CTb) which was transported from the retinal ganglion cells were intermingled with GRP-immunoreactive cell bodies and processes in the ventrolateral portion of the SCN. Ultrastructural analysis revealed that CTb-immunoreactive retinal terminals made synaptic contacts with GRP-immunoreactive dendritic processes. These results demonstrated that photic information is directly input from the optic nerve to GRP neurons in the SCN and these GRP neurons may be involved in circadian entrainment by light.     

Organization of projections from the basomedial nucleus of the amygdala: a PHAL study in the rat

The organization of axonal projections from the basomedial nucleus of the amygdala (BMA) was examined with the Phaseolus vulgaris leucoagglutinin (PHAL) method in adult male rats. The anterior and posterior parts of the BMA, recognized on cytoarchitectonic grounds, display very different projection patterns. Within the amygdala, the anterior basomedial nucleus (BMAa) heavily innervates the central, medial, and anterior cortical nuclei. In contrast, the posterior basomedial nucleus (BMAp) sends a dense projection to the lateral nucleus, and to restricted parts of the central and medial nuclei. Extra-amygdalar projections from the BMA are divided into ascending and descending components. The former end in the cerebral cortex, striatum, and septum. The BMAa mainly innervates olfactory (piriform, transitional) and insular areas, whereas the BMAp also innervates inferior temporal (perirhinal, ectorhinal) and medial prefrontal (infralimbic, prelimbic) areas and the hippocampal formation. Within the striatum, the BMAa densely innervates the striatal fundus, whereas the nucleus accumbens receives a heavy input from the BMAp. Both parts of the BMA send massive projections to distinct regions of the bed nuclei of the stria terminalis. Descending projections from the BMA end primarily in the hypothalamus. The BMAa sends a major input to the lateral hypothalamic area, whereas the BMAp innervates the ventromedial nucleus particularly heavily. Injections were also placed in the anterior cortical nucleus (COAa), a cell group superficially adjacent to the BMAa. PHAL-labeled axons from this cell group mainly ascend into the amygdala and olfactory areas, and descend into the thalamus and lateral hypothalamic area. Based on connections, the COAa and BMAa are part of the same functional system. The results suggest that cytoarchitectonically distinct anterior and posterior parts of the BMA are also hodologically distinct and form parts of distinct anatomical circuits probably involved in mediating different behaviors (for example, feeding and social behaviors vs. emotion-related learning, respectively).     

Organization of the intrinsic connections of the monkey amygdaloid complex: projections originating in the lateral nucleus

We have used the anterograde tracer, Phaseolus vulgaris-leucoagglutinin (PHA-L) to study the intrinsic projections of the lateral nucleus of the Macaca fascicularis monkey amygdaloid complex. A reanalysis of the monkey lateral nucleus indicated that there are at least four distinct cytoarchitectonic divisions: dorsal, dorsal intermediate, ventral intermediate, and ventral. The major projections within the lateral nucleus originate in the dorsal, dorsal intermediate, and ventral intermediate divisions and terminate in the ventral division. The ventral division also projects to itself but does not project significantly to the other divisions of the lateral nucleus. Thus, the ventral division appears to be a site of convergence for information entering all other portions of the lateral nucleus. There are substantial regional and topographic differences in the projections from each of the lateral nucleus divisions to other amygdaloid nuclei. The dorsal division projects to all divisions of the basal and accessory basal nuclei, to the periamygdaloid cortex, the nucleus of the lateral olfactory tract, the dorsal division of the amygdalohippocampal area, and the lateral capsular nuclei. The dorsal intermediate division projects to the intermediate and parvicellular divisions of the basal nucleus, to the parvicellular division of the accessory basal nucleus, and to the periamygdaloid cortex. The ventral intermediate division projects to the magnocellular division of the accessory basal nucleus and to the parvicellular division of the basal nucleus. The major projections from the ventral division are directed to the parvicellular division of the basal nucleus, the parvicellular division of the accessory basal nucleus, the medial nucleus, and the periamygdaloid cortex. Projections from all portions of the lateral nucleus to the central nucleus are generally very light. It appears, therefore, that each division of the lateral nucleus originates topographically organized projections to the other amygdaloid areas that terminate in distinct portions of the target regions. The topographic organization of intrinsic amygdaloid projections raises the possibility that serial and parallel sensory processing may take place within the amygdaloid complex.     

Central projections of persistent larval sensory neurons prefigure adult sensory pathways in the CNS of Drosophila

We have used a GAL4 enhancer-trap line driving the expression of a lacZ construct to examine the reorganisation of an identified group of proprioceptive sensory neurons during metamorphosis in Drosophila. The results show that whilst most larval sensory neurons degenerate during the first 24 hours of metamorphosis a segmentally repeated array of 6 neurons per segment persists into the adult stages to become functional adult neurons. These sensory neurons retain their axonal projections in the central nervous system intact and unchanged throughout. The adult sensory neuron axons enter the central nervous system at around 44 hours after puparium formation. Most of these axons grow along the pathways defined by the persistent larval sensory axons. The ordering of the adult sensory projections is, therefore, established upon the larval pattern of projections. The possibility that the larval neurons act as guidance cues for organising the ordered arrays of sensory neurons is discussed.     

Descending projections from the nucleus raphe obscurus to pudendal motoneurons in the male rat

Previous physiological and behavioral studies have shown that the nucleus raphe obscurus (nRO) modulates pelvic floor reflex function (Yamanouchi and Kakeyama [1992] Physiol. Behav. 51:575-579; Beattie et al. [1996] Soc. Neurosci. Abstr. 22:722.4; Holmes et al. [1997] Brain Res. 759:197-204). In the present study, small injections of fluorescent tracers were used to investigate direct descending projections from the rostral and caudal portions of the brainstem nRO to retrogradely labeled pudendal motoneurons (MN) in the male rat. The caudal nRO projects into the ventral and lateral funiculi of the spinal cord, with arborizations in the thoracic intermediolateral cell column; in laminae VII, IX, and X of the lumbosacral cord; and in the sacral parasympathetic nucleus (SPN). Many identified external anal sphincter and ischiocavernosus MNs appeared to be in direct apposition with fibers originating from the caudal nRO; and more than half of the bulbospongiosus MNs that were identified appeared to receive such descending input. In addition to the nRO spinal autonomic and pudendal motoneuronal targets, projections were observed to regions of the intermediate gray that contain interneurons organizing the pelvic floor reflexes and to MN pools that are involved in functionally related somatic activities. Finally, several neurons in the lumbar enlargement were labeled retrogradely with FluoroRuby after injections into the nRO and the immediately adjacent reticular formation. Thus, the nRO may be in a position to modulate the coordinated actions of autonomic preganglionic and functionally related skeletal MN activity involved in sexual and eliminative reflex functions.     

Preproenkephalin messenger RNA-expressing neurons in the rat parabrachial nucleus: subnuclear organization and projections to the intralaminar thalamus

The pontine parabrachial nucleus, which is a key structure in the central processing of autonomic, nociceptive and gustatory information, is rich in a variety of neuropeptides. In this study we have analysed the distribution of parabrachial neurons that express preproenkephalin messenger RNA, which encodes for the precursor protein for enkephalin opioids. Using an in situ hybridization method, we found that preproenkephalin messenger RNA-expressing neurons were present in large numbers in four major areas of the parabrachial nucleus: the K?lliker-Fuse nucleus, the external lateral subnucleus, the ventral lateral subnucleus, and in and near the internal lateral subnucleus. Many preproenkephalin messenger RNA-expressing neurons were also seen in the central lateral subnucleus, and in the medial and external medial subnuclei. Few labeled neurons were found in the dorsal and superior lateral subnuclei. Injection of the retrograde tracer substance cholera toxin subunit B into the midline and intralaminar thalamus demonstrated that the enkephalinergic neurons in and near the internal lateral subnucleus were thalamic-projecting neurons. Taken together with the results of previous tract-tracing studies, the present findings show that many of the enkephalinergic cell groups in the parabrachial nucleus are located within the terminal zones of the ascending projections that originate from nociresponsive neurons in the medullary dorsal horn and spinal cord, as well as from viscerosensory neurons within the nucleus of the solitary tract. The enkephalinergic neurons in the parabrachial nucleus may thus transmit noci- and visceroceptive-related information to their efferent targets. On the basis of the present and previous observations, we conclude that these targets include the intralaminar and midline thalamus, the ventrolateral medulla and the spinal cord. Through these connections, nociceptive and visceroceptive stimuli may influence several functions, such as arousal, respiration and antinociception.     

Collateral projections of gamma-aminobutyric acid positive neurons from the lateral superior nucleus to the cochlea and cochlear nucleus in guinea pigs

Collateral projections of gamma-aminobutyric acid (GABA) neurons from the lateral superior olivary nucleus (LSO) to the cochlea and cochlear nuclei in the guinea pigs were studied by injection of two retrograde fluorescent neuronal tracers. For experiments, fast blue (FB) was injected into the scala tympani of one cochlea and diamidine yellow (DY) was injected into cochlear nuclei of the same side. The results showed that the FB-labelled cells and DY-labelled cells constituted approximately 80.8% and 12.4%, respectively; FB and DY double-labelled cells constituted about 6%; FB and DY labelled cells with GABA constituted about 0.7% in the ipsilateral LSO. In the contralateral LSO, the FB and DY labelled cells were less than those of ipsilateral LSO and no FB-DY double-labelled cells could be found. Our results suggest that there are collateral projections of GABA neurons from ipsilateral LSO to the organ of Corti and cochlear nuclei in the guinea pig, even though the numbers are few. The results also show that the efferent projections to the cochlea and cochlear nuclei generally come from two different auditory neuronal nuclei.     

Direct projections from nucleus X to the external cortex of the inferior colliculus in the rat

Direct projections from nucleus X to the external cortex of the inferior colliculus (ICe) were found in the rat by the retrograde single- and double-labeling methods. The projections are bilateral with a clear contralateral dominance. Some of these projections are made by axon collaterals of projection fibers from nucleus X to the ventrobasal thalamus. On the other hand, projection fibers from nucleus X to the cerebellum send no axon collaterals to ICe.     

Firing properties of head direction cells in the rat anterior thalamic nucleus: dependence on vestibular input

Vestibular information influences spatial orientation and navigation in laboratory animals and humans. Neurons within the rat anterior thalamus encode the directional heading of the animal in absolute space. These neurons, referred to as head direction (HD) cells, fire selectively when the rat points its head in a specific direction in the horizontal plane with respect to the external laboratory reference frame. HD cells are thought to represent an essential component of a neural network that processes allocentric spatial information. The functional properties of HD cells may be dependent on vestibular input. Here, anterior thalamic HD cells were recorded before and after sodium arsanilate-induced vestibular system lesion. Vestibular lesions abolished the directional firing properties of HD cells. The time course of disruption in the directional firing properties paralleled the loss of vestibular function. Arsanilate-treated rats exhibited only minor changes in locomotor behavior, which were unlikely to account for the loss of direction-specific firing. Vestibular lesions also disrupted the influence of angular head velocity on anterior thalamic single-unit firing rates. Finally, a subset of anterior thalamic neurons recorded from vestibular-lesioned rats exhibited a pattern of intermittent firing bursts that were distinctly unrelated to HD. This novel anterior thalamic firing pattern has not been encountered in any vestibular-intact rat. These data suggest that: (1) the neural code for directional bearing is critically dependent on vestibular information; and (2) this loss of HD cell information may represent a neurobiological mechanism to account for the orientation and navigational deficits observed after vestibular dysfunction.     

The nucleus negatively controls the synthesis of mitochondrial proteins in the sea urchin egg

Enucleation of Paracentrotus lividus eggs, followed by parthenogenetic activation induces a sharp increase in the synthesis of mitochondrial proteins as shown by electrofluorography after in vivo labeling with radioactive amino acids. These results further substantiate the hypothesis that the cell nucleus negatively controls mitochondrial replication in the sea urchin egg.     

The topographical organization of descending projections from the central nucleus of the inferior colliculus in guinea pig

We describe the descending projections from the central nucleus of the inferior colliculus (CNIC) in guinea pig. Focal injections of the tracer biocytin, made in physiologically defined frequency regions of the CNIC, labelled laminated axonal terminal fields in the ipsilateral dorsal nucleus of the lateral lemniscus, and bilaterally in the ventral nucleus of the trapezoid body and the dorsal cochlear nucleus. Labelling was also present in the rostral periolivary nucleus, but we could not distinguish a clear border between the terminal fields in this nucleus and those in the ventral nucleus of the trapezoid body. Labelling observed in the ventral nucleus of the lateral lemniscus, and to a lesser extent in the dorsal nucleus of the lateral lemniscus, was accompanied by retrogradely labelled somata and therefore we cannot conclude unequivocally that the CNIC projects to these lemniscal nuclei. Where the labelling was ordered topographically, its position varied as a function of the best frequency at the injection site. High-frequency regions in the CNIC project to the medial parts of the ventral nucleus of the trapezoid body and dorsal cochlear nucleus, while low-frequency regions in the CNIC project to the lateral parts of the ventral nucleus of the trapezoid body and dorsal cochlear nucleus. Additional axonal labelling with terminal boutons, but with no apparent topographical arrangement, was present in the ipsilateral horizontal cell group, sagulum, and also bilaterally in the superficial granule cell layer of the ventral cochlear nucleus and layer 2 of the dorsal cochlear nucleus. Our findings are consistent with the existence of tonotopically organised feedback projections from the CNIC to the brainstem nuclei that project to it.