Processing of proenkephalin is tissue-specific.

Most neuropeptides are synthesized as large precursor proteins. These precursors undergo a maturation process involving several proteolytic events that generate the biologically active peptides. The enzymatic mechanisms underlying this processing are still largely unknown. The processing of the precursor protein proenkephalin was studied in two different bovine tissues, the hypothalamus and adrenal medulla. The high molecular weight enkephalin-containing peptides that accumulate in these two tissues were found to be different, indicating the existence of two processing pathways for this neuropeptide precursor.

In memory of Amico Bignami (1930-1994).

Amico Bignami, neuropathologist and neuroscientist, professor of Neuropathology at Harvard Medical School, died on August 5, 1994. He is best known for his pioneering work on spongiform encephalopathies and intermediate filaments, in particular glial fibrillary acidic protein (GFAP).

Distribution of cells containing mRNA encoding cholecystokinin in the rat central nervous system.

The distribution of cells containing mRNA encoding cholecystokinin was studied in the rat central nervous system by in situ hybridization histochemistry. Cholecystokinin mRNA containing neurons were considerably more numerous than the cholecystokinin-like immunoreactive neurons detected by immunocytochemistry even after colchicine pretreatment and appeared to be heavily, moderately, or lightly labeled. Such neurons were present in the olfactory bulb, olfactory nuclei, layers II-III and V-VI of the cerebral cortex, amygdaloid nuclei, subiculum, hippocampus, claustrum, endopiriform nucleus, several hypothalamic nuclei, most of the thalamic nuclei, ventral tegmental area, substantia nigra, interfascicularis nucleus, linearis rostralis, central gray, Edinger-Westphal nucleus, superior and inferior colliculi, parabrachial nucleus, reticular formation, raphe nuclei, and spinal trigeminal nucleus. This distribution partly confirmed and partly extended the previous immunohistochemical descriptions. Several brain areas such as the thalamus and the colliculi contain cholecystokinin mRNA but are devoid of perikarya exhibiting cholecystokinin-like immunoreactivity. The cerebral cortex and the hippocampus present a far higher density of cholecystokinin mRNA containing cells, including pyramidal neurons, than of perikarya containing cholecystokinin-like immunoreactivity. These results suggest that cholecystokinin or cholecystokinin-related peptides could have a functional role in numerous cerebral pathways including long projections such as cortical or thalamic projections.

Ontogeny of gene expression of adenosine A2 receptor in the striatum: early localization in the patch compartment.

The ontogeny of adenosine A2 receptor mRNA and adenosine A2 binding sites distributions was studied by in situ hybridization histochemistry and receptor autoradiography in pre- and post-natal rat striatum, postnatal dog striatum, and a human fetus striatum and compared to that of dopamine D1 and mu opiate receptors. The early postnatal striatum demonstrated heterogeneous distributions of adenosine A2 receptor mRNA and adenosine A2 binding sites with patches of dense labeling corresponding to dopamine D1 and mu opiate receptors enriched zones. This patchy pattern evolved to the homogeneous distribution observed in the adult. The higher intensity of adenosine A2 receptor mRNA enriched patches correspond at the microscopical level to a higher density of labeled neurons in the patches areas and also to a higher level of expression per labeled patches neuron than in the matrix ones. This demonstrates for the first time that differences in patch/matrix receptor density is at least partly linked to different levels of receptor gene expression.

Distribution of the neurons containing inositol 1,4,5-trisphosphate 3-kinase and its messenger RNA in the developing rat brain.

As a result of its interaction with a specific receptor, inositol 1,4,5-trisphosphate (InsP3) mobilizes intracellular calcium. The metabolism of InsP3 is rather complex: InsP3 3-kinase produces Inositol 1,3,4,5-tetrakisphosphate (InsP4), a putative second messenger also involved in the intraneuronal calcium homeostasis. The distribution of the messenger RNA coding for the recently cloned InsP3 3-kinase was studied in the developing rat brain by using oligonucleotides derived from the rat cDNA sequence and in situ hybridization combined with Northern blot analysis. In addition, the locations of the enzyme were determined by immunohistochemistry in combination with Western blot analysis. By Northern blot and Western blot analyses on rat brain, the kinase was not detected in the embryo, was first found slightly at birth, and reached adult levels around 2-3 postnatal weeks. These findings were confirmed in the different positive regions by in situ hybridization conducted at the macroscopic level. At the cellular level, the mRNA was found exclusively in the neuronal populations previously demonstrated in the adult. The levels of transcripts per neuron were however higher in the adult than in the neonate brain. The enzyme mRNA could be detected first at postnatal day 0, (birth, P0) in the perikarya of the cerebellar Purkinje cells, followed at P4 by the hippocampal CA1 pyramidal cells and granule cells of the dentate gyrus and finally, at P9, by a majority of the neurons in the cortical layers II-III and V, especially in the frontal cortex and cingulate cortex; claustrum; caudate, putamen, accumbens, olfactory tubercle and calleja islets; anterior olfactory nucleus; taenia tecta; piriform piriform cortex; dorsolateral septum; bed nucleus stria terminalis; amygdala; hippocampal CA2-4 sectors and subiculum. By immunohistochemistry, the enzyme was initially found in the periphery of the cell bodies of the neonatal neurons; was progressively enriched in the developing dendritic arborization during the first postnatal weeks where it remained exclusively localized in the adult. In conclusion, in the developing brain, InsP3 3-kinase was first detected at birth, and thereafter its concentrations increased to reach adult levels around 2-3 postnatal weeks. At the cellular level, the kinase was exclusively found in the neurons. The small amounts of transcripts found per neuron in the neonate increase during synaptogenesis and the protein became progressively enriched in the developing dendritic arborization, where it is localized in the adult.

Substance P, enkephalins, somatostatin, cholecystokinin, oxytocin, and vasopressin in human spinal cord.

Several neuropeptides were immunohistologically studied in normal human spinal cords. Substance P, methionine-enkephalin, leucine-enkephalin, and cholecystokinin positive fibers were found in all cytoarchitectonic layers, with a specific distribution pattern for each peptide. Somatostatin, oxytocin, and vasopressin immunoreactivities were restricted to particular spinal layers. Perikarya and proximal dendrites were visualized and classified by comparison with previous Golgi analyses. Substance P was contained in "radiate cells" of layer III, methionine-enkephalin in marginal neurons as well as in layer II "stellate cells," and somatostatin in layer II "islet cells." Several results differed from those reported in other species. Chemical neuroanatomy may provide new insights into the neuronal organization of the human spinal cord.

Cerebral amyloid angiopathy as a cause of multiple intracerebral hemorrhages.

Clinical and pathologic findings in six autopsies and five biopsies of cerebral amyloid angiopathy associated with cerebromeningeal hemorrhages are presented. One patient had experienced a previous meningeal hemorrhage. Only two had chronic hypertension; the multiple fresh hematomas found in all the autopsied brains always spared the basal ganglia and brainstem, as did vascular lesions, which were mostly cortical and meningeal. Extensive lesions of Alzheimer's disease were found in the autopsied cases with dementia. The most significant feature for clinical diagnosis of hemorrhagic cerebral amyloid angiopathy is the presence of multiple hemorrhages in unusual locations in the absence of hypertension.

Fatal familial insomnia: clinical and pathologic study of five new cases.

In 1986, we reported two anatomoclinical observations of a familial condition that we called "fatal familial insomnia" (FFI). We now present the pedigree as well as the clinical and neuropathologic findings in five new subjects. The pedigree includes 288 members from six generations. Men and women are affected in a pattern consistent with an autosomal dominant inheritance. The age of onset of the disease varies between 37 and 61 years; the course averages 13 months with a range of 7 to 25 months. Progressive insomnia (polygraphically proven in two cases); autonomic disturbances including hyperhidrosis, hyperthermia, tachycardia, and hypertension; and motor abnormalities including ataxia, myoclonus, and pyramidal dysfunction, were present in every case, but with variable severity and time of presentation. Sleep and autonomic disorders were the earliest signs in two subjects, motor abnormalities were dominant in one, and others had intermediate clinical patterns. Pathologically, all the cases had severe atrophy of the anterior ventral and mediodorsal thalamic nuclei. Other thalamic nuclei were less severely and inconsistently affected. In addition, most of the cases had gliosis of the cerebral cortex, a moderate degree of cerebellar atrophy with "torpedoes," and severe atrophy of the inferior olivary nuclei. One case also showed spongy degeneration of the cerebral cortex. We conclude that all the lesions were primary, and that FFI is a multisystem disease in which the different structures are primarily affected with different severity. The insomnia appears to correlate best with the major thalamic pathology. The possibility that FFI belongs to the group identified as prion diseases or diseases transmitted by unconventional agents is examined.

Distribution of neuronal cannabinoid receptor in the adult rat brain: a comparative receptor binding radioautography and in situ hybridization histochemistry.

The neuronal distribution of cannabinoid receptor in the adult rat brain is reported, combining receptor binding radioautography using the synthetic psychoactive cannabinoid ligand CP55,940 with in situ hybridization histochemistry using oligonucleotide probes complementary to rat cannabinoid receptor cDNA. In the cerebral cortex, especially in the frontal and cingulate cortex, dense binding was found in layers I and VI together with slight mRNA levels in a majority of both pyramidal and non-pyramidal-shaped neurons and of high mRNA levels in a moderate number of non-pyramidal-shaped neurons especially in layers II-III and V-VI. In the hippocampal dentate gyrus, very dense staining was found in the molecular layer together with high mRNA levels in a moderate number of hilar neurons close to the granular layer. In Ammon's horn, especially in the CA3 sector, very dense binding was found in the dendritic layers together with slight mRNA levels in the majority of the pyramidal cells and high mRNA levels in a moderate number of interneurons. In the basal ganglia, binding was very dense in the lateral putamen, substantia nigra pars reticulata, globus pallidus and entopeduncular nucleus, moderate in the medial putamen and caudate; and slight in the accumbens, together with slight to moderate mRNA levels in the striatal medium-sized neurons. Together with slight binding, slight to moderate mRNA levels were found in the majority of the neurons in the subthalamic nucleus. No binding and mRNA were found in the substantia nigra pars compacta and ventral tegmental area. Slight to moderate binding was found together with slight to moderate mRNA levels in the majority of neurons in the anterior olfactory nucleus; septum, especially medial septum and diagonal band of Broca; amygdala, especially basolateral amygdala; lateral habenula; ventromedial hypothalamic nucleus; lateral interpeduncular nucleus; central gray, dorsal cochlear nucleus; parabrachial nucleus; dorsal pontine tegmentum; pontine nuclei; commissural part of the nucleus tractus solitarius; inferior olive and dorsal horn of the spinal cord. In the cerebellum, very dense binding was found in the molecular layer together with slight mRNA levels in the majority of the granule cells and moderate mRNA levels in the basket and stellate cells. In conclusion, this study provides, for the first time, indirect assessment of the neurons containing cannabinoid receptor in the entire adult rat brain and will serve as a basis for future direct morphological confirmation using receptor immunohistochemistry and for functional studies.

Lesion of the nigrostriatal pathway induces cholecystokinin messenger RNA expression in the rat striatum. An in situ hybridization histochemistry study.

In situ hybridization histochemistry was used to investigate the putative regulation of cholecystokinin messenger RNA expression by dopamine in the rat striatum. Using this method, cholecystokinin messenger RNA was undetectable in the normal rat striatum. Dopamine depletion caused by a 6-hydroxydopamine injection in the medical forebrain bundle induced, two and four weeks after the injection, an increase of cholecystokinin messenger RNA expression in the ipsilateral striatum. The labeling was mostly restricted to the dorsolateral quadrant. At the cellular level, this corresponded to a slight but significant labeling of a moderate density of striatal neurons which most probably represent a subpopulation of medium-sized spiny neurons. Conversely, treatment with either haloperidol or SCH23390 for two weeks did not induce any detectable changes in cholecystokinin messenger RNA expression in the striatum while, as expected, an increase in the striatal enkephalin messenger RNA content was observed. These results suggest that the dopaminergic nigrostriatal pathway directly, or indirectly, regulates the expression of cholecystokinin messenger RNA in the striatum.

Caffeine regulates neurotensin and cholecystokinin messenger RNA expression in the rat striatum.

Interactions between dopamine and neurotensin or dopamine and cholecystokinin have been demonstrated in the basal ganglia. Disruption of nigrostriatal dopaminergic transmission results in a dramatic increase in neurotensin messenger RNA and in an induction of cholecystokinin messenger RNA in the striatum. Interaction between striatal dopaminergic and adenosinergic systems have also been reported. Adenosine and the adenosine receptor antagonist, caffeine, regulate gene expression in the striatum. In the present study, in situ hybridization histochemistry was used to investigate the putative regulation of neurotensin and cholecystokinin messenger RNA expression by caffeine in the rat striatum. Using this method, cholecystokinin messenger RNA was undetectable and neurotensin messenger RNA very sparse in the normal striatum. Chronic caffeine administration induced a dramatic increase in neurotensin messenger RNA in the subcallosal region of the caudate-putamen and a moderate increase in the shell sector of the accumbens nucleus. Similarly, caffeine induced a significant striatal expression of cholecystokinin messenger RNA in the dorsolateral and ventrolateral quadrants but was not restricted to the subcallosal area. At the cellular level, this corresponded to a significant labeling of a moderate to high density of medium-sized striatal neurons. These distributions were identical to those of neurotensin and cholecystokinin messenger RNAs observed in the case of disruption of dopaminergic transmission. We therefore concluded that in the intact striatum normally innervated by dopaminergic fibers, caffeine, probably acting through a presynaptic A2 receptor, induced a relative dopamine depletion which in turn led to the induction of neurotensin and cholecystokinin expression in subsets of striatal neurons.

Immunohistochemical distribution of neurons containing the G-proteins Gq alpha/G11 alpha in the adult rat brain.

A new class of G-proteins, the Gq family, has been recently identified and found to be involved in phospholipase C activation. The alpha subunits of the Gq and G11 members of this family are separate polypeptides but appear to have the same function. In this study, the cellular distribution in the adult rat brain of these G-proteins, Gq alpha/G11 alpha, was determined by immunohistochemistry using an antipeptide antiserum directed against the predicted C-terminal decapeptide which is conserved between these polypeptides. The specificity of the antiserum was verified by Western blot analysis using rat brain homogenates. Immunoreactivity was detected in neurons, where it was localized in the dendrites and at the periphery of the cell bodies. The staining was abundant in the dendrites of cerebellar Purkinje cells and hippocampal CA1 pyramidal cells. Staining was also found in neurons in the olfactory bulb, minor and major islets of Calleja, anterior olfactory nuclei and piriform cortex; the different cortical areas especially in their superficial layers; caudate-putamen, accumbens and olfactory tubercle; lateral septum and amygdala; hippocampal CA2-4 sectors of Ammon's horn, dentate gyrus and hilus; hypothalamic supraoptic nucleus; cerebellar granular layer; colliculi and superficial layers of the dorsal horn of the spinal cord. In conclusion, the brain neuronal localizations of Gq alpha/G11 alpha match that of phospholipase C, 1,4,5-triphosphate receptor and, to a lesser extent 1,4,5-triphosphate-3-kinase.

Comparison of neuronal inositol 1,4,5-trisphosphate 3-kinase and receptor mRNA distributions in the adult rat brain using in situ hybridization histochemistry.

As a result of its interaction with a specific receptor, inositol 1,4,5-trisphosphate mobilizes intracellular calcium. The metabolism of inositol 1,4,5-trisphosphate is rather complex: inositol 1,4,5-trisphosphate 3-kinase produces inositol 1,3,4,5-tetrakisphosphate, a putative second messenger. In order to elucidate inositol 1,3,4,5-tetrakisphosphate function, a comparative in situ hybridization study of the distributions of inositol 1,4,5-trisphosphate 3-kinase and receptor mRNAs was performed in the adult rat brain using oligonucleotides derived from their cDNA sequences. The neuronal distributions of the mRNA for the receptor were larger than for the kinase. Highest levels of both mRNAs were found in the cerebellar Purkinje cells, where they were enriched in their neuronal perikarya and to a lesser extent in their dendrites. In addition to the cerebellum, mRNAs were mainly detected in the hippocampal pyramidal cells of the CA1 sector of the Ammon's horn and in the granule cells of the dentate gyrus, and also in a majority of the neurons in the cortical layers II-III and V, especially in the frontal cortex and cingulate cortex; caudate-putamen, accumbens, olfactory tubercle and Calleja islets; claustrum; anterior olfactory nucleus; taenia tecta; piriform cortex; dorsolateral septum; bed nucleus stria terminalis; amygdala; hippocampal CA2-4 sectors and subiculum. The inositol 1,4,5-trisphosphate receptor mRNA but not kinase mRNA was found in a majority of the neurons in the thalamus, especially in the parafascicular nucleus; hypothalamus, especially the medial hypothalamus; substantia nigra pars compacta and ventral tegmental area; superior colliculus; lateral interpeduncular nucleus and central gray. Taking into account the limitation in sensitivity of the technique, both mRNAs were not detected in glial cells and in the olfactory bulb; basal nucleus of Meynert, diagonal band nuclei; medial septal nucleus; substantia innominata; globus pallidus; entopeduncular nucleus; substantia nigra pars reticulata; ventral pallidum; subthalamic nucleus; spinal cord and dorsal root ganglia. In conclusion, cerebellum and hippocampus appear to contain almost similar levels of kinase mRNA. This is in contrast to receptor mRNA levels which were at much higher levels in the cerebellum when compared with the hippocampus. For this reason, we have chosen hippocampal CA1 pyramidal cells and dentate gyrus granule cells for studying inositol 1,4,5-trisphosphate 3-kinase function.

Effect of sensory deafferentation on the GABAergic circuitry of the adult cat visual system.

The effect of bilateral central retinal lesions on the GAD67 and GAD65 messenger RNA levels in the dorsal lateral geniculate nucleus, the perigeniculate nucleus and the visual cortex of the adult cat was investigated by in situ hybridization. Three days post-lesion, a decrease in the number of GAD67-expressing cells was apparent in the deafferented dorsal lateral geniculate nucleus. This decrease persisted until 7.5 months post-lesion and was more pronounced with longer survival times. The decrease in GAD67 mRNA was mirrored by a decrease in glutamate decarboxylase-immunoreactive cells. GAD65 messenger RNA expression levels were low in the dorsal lateral geniculate nucleus of both control and retinally-lesioned cats. In the perigeniculate nucleus the messenger RNA levels of both glutamate decarboxylase isoforms were clearly decreased over a restricted region. In the lesion-affected visual cortex, no changes at the messenger RNA level were observed for either GAD67 or GAD65 although changes in glutamate decarboxylase immunoreactivity have been previously described. Hence, in the dorsal lateral geniculate nucleus, the perigeniculate nuclcus and the visual cortex, different intracellular mechanisms seem to lead to decreased GABAergic inhibition in response to sensory deafferentation.

Homolateral cerebrocortical changes in neuropeptide and receptor expression after minimal cortical infarction.

A cortical infarct of 2 mm diameter was obtained in the parietal cortex after a craniotomy, disruption of the dura mater and topical application of 3 M KCl. It has been shown previously that the presence of a small cortical infarct induces an increase in immediate early gene messenger RNA expression followed by an increase in neuropeptide and glutamic acid decarboxylase messenger RNA expression. Glutamate, acting at N-methyl-D-aspartate receptors, is held responsible for these changes, since they are blocked by pretreatment with dizocilpine. In the present study, we have analysed the consequences of the dramatic changes in messenger RNA expression on the level of immediate early gene products c-fos and zif 268, and on that of neuropeptides by using immunohistochemistry. After just 1 h, an increase in c-fos- and zif 268-like immunoreactivity is observed in the entire cortical hemisphere homolateral to the infarct, and is no longer detected after 6 h. An increase in cholecystokinin octapeptide-, substance P-, neuropeptide Y- and somatostatin-like immunoreactivity is observed in the entire cortical hemisphere homolateral to the infarct after three days, and is no longer detected after 30 days. To investigate if these dramatic increases in neuropeptide immunoreactivities may have functional consequences, we studied the level of cholecystokinin receptors by autoradiographic binding using [125I]cholecystokinin-8S and in situ hybridization for the detection of cholecystokinin-b receptor messenger RNA. A decrease in cholecystokinin binding sites and cholecystokinin-b receptor messenger RNA is observed in the entire cortical hemisphere homolateral to the infarct after three days, and is no longer detected after nine days. This study shows that a topical stimulation has diffuse effects, reaching regions far from the site of the lesion, and some of them are still strongly present after nine days. The increase in neuropeptide messenger RNAs is followed by an increase in the protein products of these genes, which may modify the neurotransmission. As a corollary to this, a decrease in cholecystokinin binding sites occurs. This may have further consequences on signal transduction pathways. This decrease in cholecystokinin binding sites is associated with a decrease in the cholecystokinin-b receptor messenger RNA, and this is the first example of a decrease in messenger RNA levels in this experimental model.

Homolateral cerebrocortical increase of immediate early gene and neurotransmitter messenger RNAs after minimal cortical lesion: blockade by N-methyl-D-aspartate antagonist.

A small surgical lesion of the parietal cortex induces an increase in the expression of several messenger RNAs varying from 172 to 980% in the entire homolateral cerebral cortex, as detected by quantitative in situ hybridization histochemistry. The messenger RNAs encoding the immediate early genes of the leucine zipper family (c-fos, c-jun, jun-B), the Zinc finger family (zif268), the glucocorticoid receptor family (NGFI-B) and the interferon family (PC4) are increased within 2 h after the lesion and return to normal levels at 6 h. The messenger RNAs encoding cholecystokinin, neuropeptide Y, somatostatin and the synthetizing enzyme of the neurotransmitter GABA, glutamate decarboxylase, are elevated within one day and return to normal levels after six days. An intraperitoneal injection of the N-methyl-D-aspartate receptor antagonist dizocilpine maleate, 30 min before surgery, prevented either the induction of immediate early gene expression or the increase of neuropeptide and glutamate decarboxylase messenger RNA expression. This study demonstrates that a minimal cortical lesion induces extensive changes in gene expression and that the mechanism(s) leading to these changes involves the action of glutamate at the N-methyl-D-aspartate receptor. These modifications may be of importance in explaining diffuse changes not related to neuronal circuitry in several conditions.

Distribution of the nociceptin and nocistatin precursor transcript in the mouse central nervous system.

The distribution of prepronociceptin messenger RNA, the recently identified endogenous ligand of the ORL1 receptor (opioid receptor-like-1), has been studied in the adult mouse central nervous system using in situ hybridization. Prepronociceptin is a new peptide precursor that generates, upon maturation, at least three bioactive peptides: nociceptin, noc2 and the recently described nocistatin. Considering both the density of labeled neurons per region and their intensity of labeling, the distribution of prepronociceptin messenger RNA-containing neurons can be summarized as follows: the highest level of prepronociceptin messenger RNA expression was detected in the septohippocampal nucleus, bed nucleus of the stria terminalis, central amygdaloid nucleus, and in selective thalamic nuclei such as the parafascicular, reticular, ventral lateral geniculate and zona incerta. High to moderate levels of prepronociceptin messenger RNA expression were detected in the lateral, ventral and medial septum, and were evident in brainstem structures implicated in descending antinociceptive pathways (e.g., the gigantocellular nucleus, raphe magnus nucleus, periaqueductal gray matter), and also observed in association with auditory relay nuclei such as the inferior colliculi, lateral lemniscus nucleus, medioventral preolivary nucleus and lateral superior nucleus. A moderate level of prepronociceptin messenger RNA expression was observed in the medial preoptic nucleus, ventromedial preoptic nucleus, periventricular nucleus, pedonculopontine tegmental nucleus, solitary tract nucleus and spinal trigeminal nucleus. A weak level of prepronociceptin messenger RNA expression was present in some areas, such as the cerebral cortex, endopiriform cortex, hippocampal formation, medial amygdaloid nucleus, anterior hypothalamic area, medial mammillary hypothalamic nuclei, retrorubral field and substantia nigra pars compacta. No labeled cells could be found in the caudate-putamen, nucleus accumbens and ventral tegmental area. The present data confirm that nociceptin is expressed in a broad array of regions of the central nervous system. In good correlation with the presently known physiological actions of nociceptin, they include, amongst others, brain areas conveying/integrating pain and auditory sensory afferences.

Substance P neurons in the human hippocampus: an immunohistochemical analysis in the infant and adult.

An analysis of the distribution of substance P immunoreactive nerve cell bodies and fibres is given for infant and adult human hippocampus by using the peroxidase-antiperoxidase technique of Sternberger. The description covers the substance P distribution in the area dentata, the Ammon's horn, the subicular complex and the entorhinal cortex. Each region shows a specific pattern in its substance P immunoreactivity. In general, the hippocampal neurons occur in three major classes of interneurons: large (20-35 microns) horizontal bipolar or multipolar neurons in the alveus, in the deep part of the subicular complex, the entorhinal cortex, and in the white matter of the angular bundle; small (10-20 microns) and large (20-35 microns) vertically oriented bipolar or multipolar neurons in the stratum oriens, in the stratum pyramidale of the Ammon's horn, and in the deep part of the subicular complex and the entorhinal cortex; large (20-35 microns) multipolar neurons in the hilus. Substance P immunoreactive fibres are particularly abundant around pyramidal cells of the CA2 and CA3 subfields of the Ammon's horn and around granule cells of the area dentata. They are also detected in the fimbria and angular bundle. Comparative study of the infant and adult hippocampus reveals no variation in the area dentata and Ammon's horn except that substance P immunoreactive fibres are more abundant in the molecular layer of the area dentata in adults. In contrast, a far more extensive number of substance P immunoreactive cell bodies are detected in the deep layers of the subicular complex and the entorhinal cortex, as well as in the white matter of the angular bundle in infants aged between three and 12 months old. This rich substance P immunoreactive network raises questions concerning its function within the human hippocampus.

Localization of the two protein kinase C beta-mRNA subtypes in cat visual system.

Protein kinase C (PKC) consists of a family of different subtypes encoded by different PKC genes. We investigated the distribution of PKC beta 1 and PKC beta 2 in the visual system of the adult cat by in situ hybridization using oligonucleotide probes complementary to the PKC beta 1 and PKC beta 2 mRNAs, two splicing variants of the same gene transcript. In the primary visual cortex PKC beta 1 and PKC beta 2 were both present. The laminar distribution patterns found for the two PKC subtypes were identical. A remarkable finding was the difference between the laminar distribution of the PKC beta s in areas 17 and 18 when compared with area 19. In all three areas the highest expression levels were found in layer VI, moderately high levels were found in layers II, III and V, while layer I was devoid of signal. In area 17 and 18 layer IV stood out by its low PKC beta signal. In sharp contrast, layer IV of area 19 was indiscernible from the superficial layers because of an evenly high signal. In the dLGN of the adult cat PKC beta 1 and PKC beta 2 mRNAs were distributed rather homogeneously over the different layers, but the expression levels for PKC beta 1 were clearly higher than those for PKC beta 2.