Neuronal peptides exert neurohormonal and neurotransmitter (neuromodulator) functions in the central nervous system (CNS). Besides these functions, a group of neuropeptides may have a capacity to create cell proliferation, growth, and survival. Axotomy induces transient (1-21 d) upregulation of synthesis and gene expression of neuropeptides, such as galanin, corticotropin releasing factor, dynorphin, calcitonin gene-related peptide, vasoactive intestinal polypeptide, cholecystokinin, angiotensin II, and neuropeptide Y. These neuropeptides are colocalized with "classic" neurotransmitters (acetylcholine, aspartate, glutamate) or neurohormones (vasopressin, oxytocin) that are downregulated by axotomy in the same neuronal cells. It is more likely that neuronal cells, in response to axotomy, increase expression of neuropeptides that promote their survival and regeneration, and may downregulate substances related to their transmitter or secretory activities.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Protein-DNA interactions during phenotypic differentiation.

We have been studying the molecular mechanism of neuronal differentiation through which the multipotent precursor becomes limited to the final transmitter phenotype. Here we focused on the role of the 5' proximal regulatory cassette (-190; +53 bp) of the rat enkephalin (rENK) gene in the developmental regulation of the enkephalin phenotype. Several well characterized cis-elements, including AP2, CREB, NF1, and NFkB, reside on this region of the rENK gene. These motifs were sufficient to confer activity-dependent expression of the gene during neurodifferentiation when it was tested using transient transfection assays of primary developing spinal cord neurons treated with tetrodotoxin (TTX). This region was then used as a DNA probe in mobility shift assays, with nuclear proteins derived from phenotypically and ontogenetically distinct brain regions. Only a few low abundance protein-DNA complexes were detected and only with nuclear proteins derived from developing but not from adult brain. The spatiotemporal pattern of these complexes did not show correlation with enkephalin expression which was assessed by RT-PCR. We employed synthetic probes corresponding to consensus as well as ENK-specific sequences of the individual motifs to identify the nature of the observed bands. Although both consensus NF1 and enkCRE1(NF1) formed complexes with nuclear proteins derived from the striatum and cortex at various ages, the appearance of the bands was not correlated with ENK expression. Surprisingly, no complexes were detected if other ENK-specific motifs were used as probes. We also tested nuclear extracts derived from forskolin-induced and control C6 glioma cells, again using the whole proximal regulatory cassette as well as individual motifs. These experiments showed the formation of elaborate protein-DNA bands. There was no direct correlation between the appearance of bands and forskolin-induced ENK expression. Unexpectedly, all ENK-specific motifs formed specific and highly abundant protein-DNA complexes when nuclear extracts from the human tumor cell line (HeLa), which does not express ENK, were used. Based on these observations, we concluded that: 1. Interactions between the proximal regulatory cassette and additional probably far distant regions of the rENK gene and their binding proteins may be necessary to confer developmentally regulated, cell-specific expression of the ENK gene; and 2. Inducibility of the gene by common cis-elements can be governed by this region; however, the cell-specificity of the induction remains elusive.

Animals↗

PubMedDate not supplied

Chronic effects of ACE-inhibition (quinapril) and angiotensin-II-type-1 receptor blockade (losartan) on atrial natriuretic peptide in brain nuclei of rats with experimental myocardial infarction.

Alterations of the central nervous system may be important for imbalance of cardiovascular and fluid regulation in heart failure. The central renin-angiotensin and atrial natriuretic peptide (ANP) systems act as mutual antagonists. The effects of angiotensin converting enzyme (ACE) inhibition (quinapril, 6 mg/kg/day) and angiotensin II type 1 (AT1) receptor blockade (losartan, 10 mg/kg/day) on ANP levels in 18 selected, microdissected brain nuclei were determined in sham-operated rats and rats with left ventricular dysfunction 8 weeks after myocardial infarction (MI). Plasma ANP tended to increase in MI rats and was further increased by quinapril. ANP was decreased in 12 brain areas of MI rats. ANP concentration was also significantly decreased by quinapril in six brain nuclei including subfornical organ and organum vasculosum laminae terminalis (areas lacking blood-brain barrier), and by losartan in 16 brain nuclei outside and within the blood-brain barrier in sham operated rats. However, both quinapril and losartan prevented a further reduction of central ANP as a result of myocardial infarction. These data suggest that there are effects on central ANP that result from chronic left ventricular dysfunction as well as an ACE-inhibitor and AT1-antagonist. Mechanisms and consequences of central ANP depression remain unclear. They could, however, support systemic vasoconstriction and sodium and fluid retention.

Angiotensin Receptor Antagonists↗

PubMedDate not supplied

Distribution and possible origin of beta-endorphin and ACTH in discrete brainstem nuclei of rats.

Immunoreactive ACTH and beta-endorphin in the lower brainstem nuclei of intact and brainstem-hemisected rats were quantified by radioimmunoassay. The distribution of these peptides was almost identical throughout the lower brainstem. The concentrations of ACTH and beta-endorphin were essentially equal when expressed on a molar basis. Both peptides were distributed unevenly in the lower brainstem. High concentrations were found in the periaqueductal central gray matter and the dorsal raphe nucleus, and moderate levels were present in the locus coeruleus, the parabrachial nuclei, the nucleus raphe magnus and in the nucleus of the solitary tract. beta-Endorphin was measurable in all 43 brainstem nuclei investigated; ACTH was non-detectable in the red and lateral cuneate nuclei. Except in certain areas in the medulla oblongata (nucleus of the solitary tract, lateral reticular nucleus, reticular formation) ACTH and beta-endorphin declined in brainstem nuclei 10 days after midbrain hemisections. Retrograde accumulation of ACTH and beta-endorphin was found in the arcuate nucleus 3 days after midbrain hemisection, which was mainly ipsilateral to the lesion. Data from brainstem-hemisected rats also indicated that ACTH and beta-endorphin in the nucleus of the solitary tract are primarily of local origin, whereas the lateral reticular nucleus (A1 and A5 catecholaminergic cell groups) and medullary reticular formation may receive ACTH and beta-endorphin innervation from both hypothalamic and medullary neurons.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Neuropeptides in the median eminence: their sources and destinations.

By radioimmunoassay and immunocytochemical techniques, 14 neuropeptides have been measured and localized in the rat median eminence. Neuropeptides with inhibitory or stimulatory effects on the anterior pituitary hormones as well as posterior pituitary hormones are present in the median eminence in the highest concentrations of the central nervous system. All these peptides (LH-RH, TRH, somatostatin, CRF, vasopressin, oxytocin) are of preoptic or hypothalamic origin and they are transported to the median eminence by loop-like fiber systems through the lateral retrochiasmatic area. Within the median eminence, the pericapillary space constitutes the main common pathway. Three major transport routes--axons, vessels, liquor spaces--are separated from each others by only basement membranes, which allow free communications downwards to the pituitary but also backwards to the central nervous system.

Animals↗

PubMedDate not supplied

Partial coexistence of growth hormone-releasing hormone and tyrosine hydroxylase in paraventricular neurons in rats.

Immunocytochemistry revealed growth hormone-releasing hormone (GRF)-containing cells (4-10/50 microns thick coronal sections) in the ventral portion of the medial parvicellular subdivision of the paraventricular nucleus (PVN) in the rat. In the same region we also detected about the same number of neurons containing the mRNA that encodes GRF using in situ hybridization histochemistry. Fluorescence double labelling immunohistochemistry showed the presence of GRF and tyrosine hydroxylase (TH) in the same PVN neurons. The overlap between the two populations of cells is only partial: less than half of TH-positive cells contain GRF and vice versa.

Animals↗

PubMedDate not supplied

Nicotine-induced alteration in Tyr-Gly-Gly and Met-enkephalin in discrete brain nuclei reflects altered enkephalin neuron activity.

Nicotine acts in CNS, but the pathways and mechanisms of its actions are poorly understood. Recent studies suggest an interaction between brain nicotinic receptors and endogenous opioid peptides. Acute administration of nicotine may alter enkephalin release without affecting brain enkephalin level. Tyr-Gly-Gly has been shown previously to be an extraneuronal metabolite of opioid peptides derived from proenkephalin A. Concentrations of Tyr-Gly-Gly in brain were used to provide an index of enkephalin release in vivo. Thus we examined the thesis that nicotine alters brain neuronal enkephalin release, by measuring Tyr-Gly-Gly levels in specific brain nuclei from rats treated with nicotine 0.3 mg/kg SC 10 min before decapitation. Of 30 brain regions investigated, acute nicotine increased Tyr-Gly-Gly immunoreactivity in nucleus accumbens and in lower brain stem areas including dorsal raphe, pontine reticular formation, gigantocellular reticular formation, locus coeruleus, sensory trigeminal nucleus and the caudal part of ventrolateral medulla oblongata. Concomitantly, nicotine produced a significant decrease in native Met-enkephalin in central amygdala, flocculo-nodular lobe of cerebellum, caudal part of the ventrolateral medulla and intermediolateral cell column of the spinal cord. It is probable that the effects of nicotine to increase Tyr-Gly-Gly and alter Met-enkephalin concentration are mediated by nicotine-induced release of enkephalin at these brain sites. Furthermore, some of the physiologic and pharmacologic effects of nicotine may be mediated by such enkephalin release.

Amino Acid Sequence↗

PubMedDate not supplied

Changes in puromycin-sensitive aminopeptidases in postmortem schizophrenic brain regions.

We studied the distribution of puromycin-sensitive aminopeptidase (PSA) in well-defined human brain ares by Western immunoblot in an attempt to examine its possible role in schizophrenia. The schizophrenic brains were from suicide victims (n = 13) of either sex, with an age range of 30-60 yr (average 45). The controls were mostly victims of myocardial infarction (n = 12), of either sex and between 32 and 56 yr old (average 44). The brain regions were obtained within 48 h after death. After ultracentrifugation the PSA was quantified by Western blot analysis using a PSA antiserum. The distribution of the two most abundant antigens, MW 100 kDa (PSA-100) and 170 kDA (PSA-170), were compared. PSA-100 had peptidase activity, PSA-170 did not. PSA-100 was found in all of the region studied. In the control brain areas prefrontal cingulate and frontal cortices, thalamus, hippocampus, hypothalamus and outer globus pallidus contained significantly more PSA-100 than the corresponding areas from schizophrenic brain. PSA-170 was mostly found only in areas of schizophrenic brains. In three control brains, in one area of each, it could be detected, but the level in each of these regions was less than 30% of that in the corresponding schizophrenic area. PSA-170 was found in all the schizophrenic brains, in 20 of the 35 regions we studied, with parahippocampal cortex the highest (134 ng/g wet tissue) and frontal inferior cortex the lowest (9.3 ng/g wet tissue). It was not detectable in cerebral or cerebellar white matter. Our data show that the amounts and distribution of PSA-170, a protein of unknown function, is restricted mostly to schizophrenic brain areas. The difference is not due either to neuroleptic treatment of the patient or to the postmortem proteolysis of the brain samples.

Adult↗

PubMedDate not supplied

Acetylcholine content in different regions of the rat brain.

Acetylcholine content of different rat brain regions was measured. A correlation between acetylcholine content and cholineacetyltransferase (ChAc) activity in discrete brain regions was found. However there are regions such as cerebellar nuclei, cerebellar hemisphere, caudal medial forebrain bundle, zone incerta, nucleus vestibularis lateralis where the acetylcholine content is relatively much higher than the ChAc activity, and regions such as n.cochleares, n.motor n.V., N.motor N.VII., n.motor, n.XII where ChAc activity was high and the content of acetylcholine is relatively low.

Acetylcholine↗

PubMedDate not supplied

Distribution of prostaglandins E and F in different regions of the rat brain.

The regional distribution of prostaglandins E and F in 24 different areas of the rat brain was studied. For bioassay the rat uterine horn preparation was used. Prior to bioassay the samples were purified with organic solvents and in some cases by chromatography on silica as well. For measurement of PGF2 alpha content in certain areas a radioimmunoassay was used. Each region was found to contain prostaglandins but in uneven concentrations. Highest concentration, related to the protein content, was present in the median eminence, 57.6 ng PGE and 34.4 ng PGF per mg protein. Parietal cortex, olfactory tubercle, cerebellar cortex, caudate nucleus, substantia nigra, and paraventricular nucleus are also rich in prostaglandins. Low values were found in frontal cortex, thalamus, and septum. The distribution of prostaglandins throughout the areas examined do not show any direct correlation with that of transmitter substances. The uneven distribution can be attributed to differences in the endogenous biosynthetic capacity of each region.

Animals↗

PubMedDate not supplied

Light and electron microscopic identification of monoaminergic terminals in the central nervous system.

A brief critical survey of methods used for light and electron microscopic examination of amine-containing pathways within the CNS. Light microscopic techniques such as fluorescence histochemistry, immunocytochemistry, autoradiography, silver degeneration techniques, and retrograde tracing technique are suitable for studying the topography of pathways but, due to limits of resolution, they are inadequate for identifying terminals. Electron microscopy which is adequate to visualize terminals does not provide an overall view. This review considers various methods which have been devised to specifically detect aminergic nerve terminals. Electrolytic and chemical induced degenerations are described in noradrenergic, dopaminergic, and serotoninergic terminals. Although the individual degenerative alterations are not specific for aminergic terminals, the degenerative process when considered as a whole can be informative. At present no single technique can provide complete information about the origin, course, connections, and terminals of aminergic systems. Concurrent application of light and electron microscopy, experimental surgery, histochemistry, and microsample biochemistry would provide a complete description.

Animals↗