Postnatal development of corticosteroid receptor immunoreactivity in the rat hippocampus.

Postnatal changes in corticosteroid receptor immunoreactivity in the rat hippocampus were examined using an antiserum against a fusion protein containing an N-terminal peptide of the Type I receptor, and a monoclonal antibody against the rat liver Type II-receptor. Age-related regional differences were observed. In the pyramidal cell layer of Ammon's horn, and granule cell layer of the dentate gyrus (DG), the percentage of Type I receptor immunoreactive (Type I-ir) and Type II receptor immunoreactive (Type II-ir) cells was high perinatally, declined sharply by postnatal day 10 (P10), and showed a variable increase to adult levels subsequently. The pyramidal cells of CA1-CA2, subiculum and DG showed a selective increase in Type II-ir in late postnatal life into adulthood, while most other regions showed higher Type I-ir in both early and late postnatal life, suggesting different roles for these receptors during development. Type II-ir was predominantly nuclear in most neurons, except for a transient appearance of cytoplasmic Type II-ir in neurons of the stratum oriens and molecular layers of Ammon's horn and dentate gyrus of P20-P30. Type I-ir was diffusely nuclear and cytoplasmic at all developmental ages. This is suggestive of differential genomic and extragenomic roles for these receptors during postnatal development of the hippocampus.     

Distribution of hippocampal cholinergic neurostimulating peptide (HCNP) immunoreactivity in the central nervous system of the rat

Hippocampal cholinergic neurostimulating peptide (HCNP), an undecapeptide isolated from the hippocampal tissue of young rats, enhances the cholinergic development in explant cultures of medial septal nuclei. This report concerns the distribution of HCNP immunoreactivity in the central nervous system (CNS) of 11- and 28-day-old Wistar rats; two affinity-purified anti HCNP antibodies were used. Immunoblot analyses of extracts of different regions of the brain revealed a single 23 kDa band that corresponded to the presumed HCNP precursor protein. Immunostaining of the various CNS structures of the 28-day-old rats was more intense than in those of 11-day-old animals. HCNP immunoreactivity was detected in neurons as well as in glia cells, particularly oligodendroglia. The perikarya of neurons in the cerebral cortex, hippocampus, limbic cortex, caudate, putamen, arcuate nucleus of hypothalamus, trigeminal subnuclei, rostroventrolateral reticular nucleus and dorsal horn of the spinal cord were positively stained. In addition, nerve fibers and terminals in the hypothalamic subnuclei, zona incerta, thalamic subnucleus, caudate, putamen, locus coeruleus, trigeminal subnuclei, dorsal motor nucleus of the vagus, dorsal horn of the spinal cord and intermediolateral column also displayed HCNP immunoreactivity. These observations would suggest that HCNP and its related molecules may have multifunctional roles in the CNS.     

Distribution of high affinity choline transporter immunoreactivity in the primate central nervous system

A mouse monoclonal antibody (clone 62-2E8) raised against a human recombinant high-affinity choline transporter (CHT)-glutathione-S-transferase fusion protein was used to determine the distribution of immunoreactive profiles containing this protein in the monkey central nervous system (CNS). Within the monkey telencephalon, CHT-immunoreactive perikarya were found in the striatum, nucleus accumbens, medial septum, vertical and horizontal limb nuclei of the diagonal band, nucleus basalis complex, and the bed nucleus of the stria terminalis. Dense fiber staining was observed within the islands of Calleja, olfactory tubercle, hippocampal complex, amygdala; moderate to light fiber staining was seen in iso- and limbic cortices. CHT-containing fibers were also present in sensory and limbic thalamic nuclei, preoptic and hypothalamic areas, and the floccular lobe of the cerebellum. In the brainstem, CHT-immunoreactive profiles were observed in the pedunculopontine and dorsolateral tegmental nuclei, the Edinger-Westphal, oculomotor, trochlear, trigeminal, abducens, facial, ambiguus, dorsal vagal motor, and hypoglossal nuclei. In the spinal cord, CHT-immunoreactive ventral horn motoneurons were seen in close apposition to intensely immunoreactive C-terminals at the level of the cervical spinal cord. CHT immunostaining revealed a similar distribution of labeled profiles in the aged human brain and spinal cord. Dual fluorescent confocal microscopy revealed that the majority of CHT immunoreactive neurons contained the specific cholinergic marker, choline acetyltransferase, at all levels of the monkey CNS. The present observations indicate that the present CHT antibody labels cholinergic structures within the primate CNS and provides an additional marker for the investigation of cholinergic neuronal function in aging and disease.     

The difference of osteocalcin-immunoreactive neurons in the rat dorsal root and trigeminal ganglia: co-expression with nociceptive transducers and central projection

The co-expression of osteocalcin (OC) with the capsaicin receptor (VR1) and vanilloid receptor 1-like receptor (VRL-1) was examined in the dorsal root (DRG) and trigeminal ganglia (TG). Virtually all OC-immunoreactive (ir) DRG neurons were devoid of VR1- and VRL-1-immunoreactivity (ir). In the TG, 14.1% of OC-ir neurons were also immunoreactive for VR1. Only 1.7% of OC-ir TG neurons co-expressed VRL-1-ir. The distribution of OC-ir was also examined in the spinal cord and trigeminal sensory nuclei. In the spinal cord, the superficial laminae of the dorsal horn were devoid of OC-ir. The neuropil was weakly stained in other regions of the spinal horns. The medullary dorsal horn (MDH) contained numerous OC-ir varicose fibers in laminae I and II. These fibers were occasionally observed originating from the spinal trigeminal tract. The neuropil was weakly stained in deeper laminae of the MDH, and the rostral parts of the trigeminal sensory nuclei. The present study suggests that OC-ir TG nociceptors send their unmyelinated axons to the superficial laminae of the MDH.     

Immunocytochemical localization of an imidazoline receptor protein in the central nervous system

Imidazoline (I) receptors have been implicated in the regulation of arterial blood pressure and behavior although their distribution in the central nervous system (CNS) remains in question. Presumptive I- receptor sites were detected in the rat central nervous system with a polyclonal antibody to an imidazoline receptor protein (IRP) with binding characteristics of the native receptor. IRP-like immunoreactivity (LI) was detected in neurons and glia by light and electron microscopy. Spinal cord: processes were heavily labeled in superficial laminae I and II of the dorsal horn, lateral-cervical and -spinal nuclei and sympathetic cell column. Medulla: label was concentrated in the area postrema, rostral, subpostremal and central subnuclei of nucleus tractus solitarii, spinal trigeminal nucleus caudalis, and inferior olivary subnuclei. Visceromotor neurons in the dorsal vagal and ambigual nuclei were surrounded by high concentrations of immunoreactive processes. In reticular formation, label was light, though predominant in the intermediate reticular zone and ventrolateral medulla. Pons: label was detected in the neuropil of the periventricular gray, concentrated in the dorsal– and external–lateral subnuclei of lateral parabrachial nucleus, and present intracellularly in the mesencephalic trigeminal nucleus. Midbrain: IRP-LI was most heavily concentrated in the interpeduncular nucleus, nuclei interfascicularis and rostral-linearis, the subcommissural organ, central gray, and in glia surrounding the cerebral aqueduct. Diencephalon: high densities were detected in the medial habenular nucleus, nucleus paraventricularis thalami, other midline-intralaminar thalamic nuclei, the supramammillary and mediobasal hypothalamic nuclei. In the median eminence, immunolabeled processes were restricted to the lamina interna and lateral subependymal zone. Telencephalon: IRP-LI was concentrated in the central amygdaloid nucleus, bed nucleus of stria terminalis and globus pallidus, followed by moderate labeling of the medial amygdaloid nucleus, amygdalostriatal zone and caudoputamen, the hilus of the dentate gyrus, and stratum lacunosum-moleculare of field CA₁ of Ammon's horn. The subfornical organ and organum vasculosum lamina terminalis were filled with diffuse granular immunoreactivity. Ultrastructural studies identified IRP-LI within glia and neurons including presynaptic processes. I-receptor(s) localize to a highly restricted network of neurons in the CNS and circumventricular regions lying outside of the blood-brain barrier. Putative imidazoline receptors have a unique distribution pattern, show partial overlap with ₂ adrenoreceptors and are heavily represented in sensory processing centers and the visceral nervous system.     

Substance P and cholecystokinin-like immunoreactive varicosities in somatosensory and autonomic regions of the rat spinal cord: a quantitative study of coexistence

Substance P- and cholecystokinin-like immunoreactivities have been shown to coexist in some, but not all, dorsal root ganglion cell bodies of the rat. Quantitative immunofluorescence techniques were used in the present study to describe densities of substance P- and cholecystokinin-like immunoreactive varicosities in several spinal cord nuclei. By combining simultaneous immunofluorescent techniques on one tissue section with computerized image processing, coexistence of substance P- and cholecystokinin-like immunoreactivity in varicosities was also quantified. By comparing spinal cord regions between normal and unilateral dorsal rhizotomy affected animals, densities of substance P- and cholecystokinin-like immunoreactive varicosities associated with primary afferent neurons were established. To determine the densities of immunoreactive varicosities that were related to unmyelinated primary afferent fibers, data were compared between normal animals and those treated neonatally with capsaicin. Four major observations were made: (1) Substance P- and cholecystokinin-like immunoreactivity coexist in populations of varicosities in sensory and autonomic regions of rat spinal segment L6. (2) Within the superficial laminae of the dorsal horn, varicosities containing both substance P- and cholecystokinin-like immunoreactivity and cholecystokinin-like immunoreactivity alone are of primary afferent neuron origin, but those containing only substance P-like immunoreactivity are most likely of spinal or descending neuronal origin. (3) Capsaicin-insensitive cholecystokinin-like immunoreactive varicosities were present predominantly in lamina I. These data suggest some cholecystokinin-like immunoreactive varicosities are associated with myelinated primary afferent neurons. (4) Primary afferent fibers containing substance P- and cholecystokinin-like immunoreactivity project to intermediate gray regions of the rat spinal cord. A large proportion of these fibers are capsaicin sensitive, suggesting that they are unmyelinated.     

Relation between putative afferent axons and the glia limitans in rat motor roots

The law of Magendie states that ventral roots channel efferent axons from the spinal cord to the periphery, while dorsal roots channel afferent axons from the periphery into the spinal cord. As primary afferent C-fibres occur in mammalian ventral roots, this law has been questioned. However, other observations suggest that ganglionic axons do not enter the spinal cord via ventral roots. The present paper examined, by double labelling immunohistochemistry, the relation between putative peripheral afferents and the PNS/CNS transition in the trigeminal motor root and in selected spinal ventral roots of the rat. The afferents were labelled with antibodies against vasoactive intestinal polypeptide, substance P or calcitonin gene-related peptide. The glia limitans at the PNS/CNS transition was defined with antibodies against glial fibrillary acidic protein. The results showed that no immunoreactive axons occurred in the trigeminal motor root. However, in all ventral roots examined, labelled axons were frequently observed. While some of these ended blindly, looped or branched in the rootlets, others shifted to the pia mater. Immunoreactive axons crossing the glia limitans at the PNS/CNS transition were not observed. Thus, the results obtained support the law of Magendie.     

HCN1 ion channel immunoreactivity in spinal cord and medulla oblongata

Hyperpolarization-activated cyclic nucleotide-gated (HCN) non-selective cation channels in neurons carry currents proposed to perform diverse functions, including the hyperpolarization activated Ih current. The 4 HCN subunits have unique but overlapping patterns of expression in the CNS. Here, we examined the distribution of HCN1 channel subunits in the brainstem and spinal cord using immunohistochemistry. At all levels of the spinal cord dorsal horn, HCN1 immunoreactivity (HCN1-IR) was predominantly absent from laminae I and II, while a dense band of punctate labeling was visible in lamina III. Labeled neurons were identified in close vicinity to the central canal, in the lateral spinal nucleus, in the ventral horn and occasionally in lamina II and III. Those in the ventral horn were identified as alpha motor neurons using retrograde tracing and/or double or triple immunostaining with neuronal markers neurofilament 200 (NF200) and choline acetyltransferase. HCN1-IR neurons in the brainstem included neurons in sensory pathways such as the dorsal column nuclei, the area postrema, the spinal trigeminal nucleus as well as identified motor neurons in motor nuclei. In the nucleus ambiguus, a mixed visceral/motor nucleus, HCN1-IR was present only in NF200-IR cells, suggesting that it is expressed in motor but not autonomic preganglionic neurons. HCN1-IR motor neurons in the nucleus ambiguus also expressed the neurokinin 1 receptor and were labeled retrogradely from the larnyx. At the light microscopic level, the NTS and inferior olive contained punctate labeling, which ultrastructural examination revealed to be present in predominantly synaptic terminals or dendrites respectively. These data therefore described the first localization of the HCN1 subunit in the spinal cord and extend previous reports from the brainstem.     

Distribution of glycine receptor immunoreactivity in the spinal cord of the rat: cytochemical evidence for a differential glycinergic control of lamina I and V nociceptive neurons

In this study we characterized the distribution of glycine receptor immunoreactivity in the spinal cord of the rat by using monoclonal antisera directed against the purified glycine receptor. There was dense, punctate glycine receptor immunoreactive staining in all regions of the gray matter ventral to the substantia gelatinosa. The densest staining was found in laminae III and IV of the dorsal horn. There were also distinct, tributarylike bands of punctate staining that extended well into the white matter of the lateral and ventral funiculi. The only consistent cell body staining was found in small neurons of the ventral horn. The labelled neurons were distributed among larger, unlabelled motoneurons. In general, the pattern of glycine receptor immunoreactivity was similar at all levels of the spinal cord and was comparable to that seen with binding of a tritiated glycine receptor antagonist, strychnine, to sections of rat spinal cord (Zarbin et al.: J. Neurosci. 1:532-547, '81). Two important exceptions, however, were observed. In contrast to the high levels of strychnine binding reported in the substantia gelatinosa, we found almost no glycine receptor immunoreactivity in laminae I and II of the superficial dorsal horn of the spinal cord or of the trigeminal nucleus caudalis. There was also a notable absence of antibody staining in the intermediolateral cell column of the thoracic cord. The presence of dense glycine receptor immunoreactivity in the region of lamina V and its absence in the superficial dorsal horn are discussed in terms of a possible differential glycinergic control of nociceptive neurons of laminae I and V.     

Ultrastructural localization of beta-arrestin-1 and -2 in rat lumbar spinal cord.

beta-arrestins play significant roles in agonist-mediated desensitization of G protein-coupled receptors. Although the presence of beta-arrestin subtypes, beta-arrestin-1 and(- 2) in rat brain has been studied extensively, their existence in the spinal cord has not been described. In the current study, we performed immunohistochemical analyses of beta-arrestins at both light and electron microscopic levels using rat lumbar 1-2 spinal cord segments. Intense immunoreactivity for beta-arrestin-1 was found in the motoneurons in lamina IX of the ventral horn and elongated cells in the dorsal nucleus of Clarke. Modest immunoreactivity was detected among the neurons of laminae V and VII/VIII, and weaker immunoreactivity in laminae III, IV, and X. beta-arrestin-2 immunoreactivity was also distributed through laminae III-X in the order of IX > dorsal nucleus of Clarke > V > VII/VIII > IV > III > X. Laminae I and II did not show immunoreactivity. At the electron microscopic level, both beta-arrestin-immunoreactive and nonimmunoreactive dendrites were observed, whereas axons and terminal boutons were devoid of immunoreactivity. In immunoreactive dendrites most beta-arrestin immunoreactivity was distributed throughout the cytoplasm, demonstrating their association with microtubules. In addition, strong immunoreactivity was often found at postsynaptic densities. Our results thus suggest beta-arrestins' possible involvement in both motor and sensory mechanisms at the postsynaptic level in rat lumbar spinal cord.     

HSV (Type 1) infection of the trigeminal complex

Following corneal inoculation with herpes simplex virus (Type 1) (HSV), virus spreads to the CNS by axonal transport in the central branches of trigeminal ganglion cell neurons. Although this mode of viral entry to the CNS is rare for humans, it appears to be the principal route of entry into the CNS in animal models of herpetic corneal disease. In this study, the corneas of BALB/c mice were unilaterally inoculated with HSV, and the distribution of HSV-immunoreactive label was studied to identify the central branches of the axons of infected trigeminal ganglion cells. Virus was first noted in the brainstem trigeminal complex 4 days after corneal inoculation, when HSV-labeled afferents were found throughout the course of the descending tract of V as well as in interstitial neurons in the tract. By 5 days labeled neurons were also found not only in the n. caudalis and portions of the n. interpolaris of the trigeminal complex but also in laminae I–IV of the dorsal horn of the upper cervical levels of the spinal cord. No immunoreactivity was seen in other regions of the complex, including the n. oralis or the main sensory n. of V. By 6 days, however, the infection had spread to the main sensory division of V.     

Development of substance P-like immunoreactivity in Xenopus embryos

The development of substance P-like immunoreactivity (SPLI) was studied in the Xenopus embryonic nervous system in order to determine in which neuronal populations and at what developmental times SPLI is expressed. Although Rohon-Beard neurons initially were thought to be the only substance P-immunoreactive cells in the embryonic frog spinal cord, we have demonstrated that several neuronal phenotypes are immunoreactive. The earliest evidence of SPLI was seen at stage 28 (Nieuwkoop and Faber, '67), at which time only some trigeminal ganglion cells, their axons in the ophthalmic nerve, and axons in the lateral tracts of the hindbrain showed SPLI. In the embryonic brain at stages 29/30, 37/38, and 42, SPLI was seen in the hypothalamus, trigeminal ganglion cells and their peripheral axons, the sensory roots of cranial nerve IX/X, and axons in the hindbrain lateral tracts. At premetamorphic stages, SPLI was found in several populations that are immunoreactive in adult amphibia. In the embryonic spinal cord, Rohon-Beard neurons were labeled consistently with reaction product; there was a rostrocaudal time gradient of immunoreactivity with increasing development. The Rohon-Beard neurons were not immunoreactive at developmental stages in which axonal outgrowth was beginning (stage 21), but were strongly immunoreactive at stages in which target cells had been contacted (stage 29). Several types of interneurons in the spinal cord (as classified by Roberts and Clarke, '82) showed SPLI during embryonic stages. At premetamorphic stages the Rohon-Beard neurons began to disappear and the immunoreactive interneurons were distributed similarly to those reported in the adult. Dorsal root ganglia differentiated during these stages, and at this time some of the neurons belonging to these ganglia exhibited substance P-like immunoreactivity.     

Immunohistochemical localization of phospholipase D1 in rat central nervous system

Phospholipase D (PLD) is one of the intracellular signal transduction enzymes and plays an important role in a variety of cellular functions. We investigated the distribution of PLD isozyme, PLD1 in the rat brain and spinal cord using an immunological approach. Western blot analysis showed the presence of PLD1 protein in all tissues studied, with significantly higher levels in the brainstem and spinal cord, which was correlated with the results obtained from PLD activity assay. Prominent and specific signals of PLD1 were observed in many functionally diverse brain areas, including the olfactory bulb, medial septum-diagonal band complex, cerebral cortex, brainstem, cerebellum, and spinal cord. In the brainstem, the red nucleus, substantia nigra, interpeduncular nucleus, cranial motor nuclei (trigeminal motor, abducent, facial, and hypoglossal), sensory cranial nerve nuclei (spinal trigeminal, vestibular, and cochlear), as well as nuclei of the reticular formation, all showed intense immunoreactivity. Purkinje cells and deep cerebellar nuclei of the cerebellum were also labeled intensely. However, no significant labeling was found in the thalamus, epithalamus, and basal ganglia. Although many of the PLD1 immunoreactive cells were neurons, PLD1 was also expressed in glial cells such as presumed astrocytes and tanycytes. These findings suggest that PLD1 may play an important role in the central nervous system of the adult rat.     

Galanin-like immunoreactivity in capsaicin sensitive sensory neurons and ganglia

In rats treated with capsaicin (CAP) as neonates, galanin-like (GA) immunoreactivity is markedly decreased in the trigeminal ganglion and the dorsal root ganglia as well as in the superficial layers of the dorsal spinal cord (laminae I and II), the substantia gelatinosa, the nucleus and tractus of the spinal trigeminal nerve and the nucleus commissuralis. Since CAP causes selective degeneration of primary sensory neurons of the C-fiber type and type B-cells of sensory ganglia, it is concluded that GA in CAP-sensitive primary sensory neurons represents a novel peptidergic system possibly involved in the transformation or modulation of peripheral nociceptive impulses. This system differs from the CAP-resistant GA-like neurons in other brain areas.     

Distribution of neurons expressing immunoreactivity for the 5HT3 receptor subtype in the rat brain and spinal cord

The cellular distribution of the type 3 serotonin receptor (5HT₃R) in the rat brain was established immunocytochemically by using a polyclonal antibody raised against a synthetic peptide from the deduced amino-acid sequence of the cloned 5HT₃R. The 5HT₃R-immunoreactive neurons were found in the forebrain, brainstem, and spinal cord, but within each region, the intensity of the immunoreactivity differed considerably. Within the forebrain, intensely immunoreactive cells were found in layers II–III of the neocortex, anterior olfactory nucleus, hippocampal formation, and amygdala. A few strongly immunoreactive neurons were consistently observed in the caudate putamen, and moderately or weakly labeled neurons were occasionally found in the nucleus accumbens. Within the brainstem, intensely labeled neurons were found in the trigeminal motor (V) and facial (VII) nuclei. Immunostained neurons were detected in the dorsal and the ventral horn of the spinal cord. These results reveal that the 5HT₃R-immunoreactive neurons are broadly distributed throughout the rat brain spinal cord, and suggest that this receptor can subserve significant participation in central nervous system neurotransmission. J. Comp. Neurol. 402:385–401, 1998. © 1998 Wiley-Liss, Inc.     

Multiple opioid peptides and the modulation of pain: immunohistochemical analysis of dynorphin and enkephalin in the trigeminal nucleus caudalis and spinal cord of the cat

Using immunocytochemistry, we have identified important differences in the distribution of immunoreactive dynorphin and enkephalin cells and terminals in the trigeminal nucleus caudalis and in the spinal dorsal horn of the cat. Dynorphin immunoreactive processes are more closely associated with those regions of cord that process nociceptive information, specifically laminae I and V. Enkephalin neurons and terminals are more widespread. Based on the staining pattern with an antiserum to the octapeptide-metenkephalin-arg-gly-leu, we suggest that the dense enkephalin terminal immunoreactivity in the inner part of the substantia gelatinosa derives from cells in lamina III. There are also significant differences in the anatomical relationship of the two opioid peptides with the organization of parasympathetic autonomic preganglionic neurons. The functional significance of these observations must await physiological analysis; nevertheless, it is almost certain that differences will be found and that these will be important in understanding the mechanisms through which exogenous opiates and a variety of descending control systems exert their effects on spinal cord neurons.     

Brain-derived neurotrophic factor-immunoreactive primary sensory neurons in the rat trigeminal ganglion and trigeminal sensory nuclei

Immunohistochemistry for brain-derived neurotrophic factor (BDNF) was performed on the rat trigeminal ganglion (TG). The immunoreactivity (IR) was detected in 46% of TG neurons. These neurons were mostly small- or medium-sized (range, 149.7-1246.3 microm2; mean +/- SD = 373.4 +/- 151.6 microm2). A double immunofluorescence method also revealed that 54% of BDNF-immunoreactive (IR) neurons were immunoreactive for calcitonin-gene-related peptide. In addition, 93% of BDNF-IR TG neurons contained vanilloid receptor subtype 1. However, the co-expression of BDNF and vanilloid receptor 1-like receptor was very rare (less than 1%). In the trigeminal sensory nuclei, laminae II of the medullary dorsal horn was abundant in presumed BDNF-IR axon terminals. Such profiles were also detected in the dorsolateral part of the subnucleus oralis. The retrograde tracing and immunohistochemical methods demonstrated that BDNF-IR was common among cutaneous TG neurons (47%) but not tooth pulp TG neurons (13%). The present study indicates that BDNF-IR TG neurons have unmyelinated axons and project to the superficial medullary dorsal horn. It is likely that BDNF-containing neurons in both the trigeminal and spinal sensory systems have similarities in morphology and function. However, the content of BDNF in TG neurons probably depends on their peripheral targets. BDNF seems to convey nociceptive cutaneous input to the trigeminal sensory nuclei.     

New members of the parathyroid hormone/parathyroid hormone receptor family: the parathyroid hormone 2 receptor and tuberoinfundibular peptide of 39 residues

The parathyroid hormone (PTH) family currently includes three peptides and three receptors. PTH regulates calcium homeostasis through bone and kidney PTH1 receptors. PTH-related peptide, probably also through PTH1 receptors, regulates skeletal, pancreatic, epidermal, and mammary gland differentiation and bladder and vascular smooth muscle relaxation and has a CNS role that is under investigation. Tuberoinfundibular peptide of 39 residues (TIP39) was recently purified from bovine hypothalamus based on selective PTH2 receptor activation. PTH2 receptor expression is greatest in the CNS, where it is concentrated in limbic, hypothalamic, and sensory areas, especially hypothalamic periventricular neurons, nerve terminals in the median eminence, superficial layers of the spinal cord dorsal horn, and the caudal part of the sensory trigeminal nucleus. It is also present in a number of endocrine cells. Thus TIP39 and PTH2 receptor-influenced functions may range from pituitary and pancreatic hormone release to pain perception. A third PTH-recognizing receptor has been found in zebrafish.     

Distribution of protein kinase C-like immunoreactive neurons in rat brain

Distribution of protein kinase C in the CNS of rat is presented based on immunohistochemical analysis with monoclonal antibodies against this protein kinase. Protein kinase C-like immunoreactivity was discretely localized and associated with neurons. Most, if not all, glial cells were not significantly stained. The greatest density of the immunoreactive material was seen in the following regions: the olfactory bulb (external plexiform layer), olfactory tuberculum, anterior olfactory nucleus, cerebral cortex (layers I and IV), pyriform cortex, hippocampus (strata radiatum and oriens), amygdaloid complex (central and basolateral nuclei), cerebellar cortex (molecular layer), dorsal cochlear nucleus, nucleus spinal tract of the trigeminal nerve, and dorsal horn of the spinal cord (substantia gelatinosa). Image analysis revealed that the regional distribution of the protein kinase C-like immunoreaction generally agreed with that of phorbol ester-binding sites. Immunoreactive perikarya were found in the following areas: the cerebral cortex (layers V and VI), caudate putamen, hippocampus, thalamus, amygdaloid complex, medial and lateral geniculate nucleus, superior colliculus, cerebellar cortex, nucleus spinal tract of the trigeminal nerve, dorsal cochlear nucleus, and dorsal horn of the spinal cord. Intense protein kinase C-like immunoreactivity in the neuron was observed both in the membrane and cytoplasm of the perikarya, dendrites, axons, and axon terminals, while weak immunoreaction was seen in the nuclei but almost never in the nucleoles. A map of protein kinase C-containing neurons was constructed. Such an uneven distribution in the brain suggests that this enzyme may play roles in controlling neuronal function in the areas noted.