Distribution of enkephalin-related peptides in rat brain: immunohistochemical studies using antisera to met-enkephalin and met-enkephalin Arg6Phe7

Detection of the mRNA coding for enkephalin precursor in the rat brain and adrenal by using an 'in situ' hybridization procedure

The messenger RNA coding for preproenkephalin A (PPA) has been detected in tissue sections of the rat brain and adrenal by using two rat PPA cDNAs labeled with 32P or 35S as probes. In the brain, neurons were labeled in areas known to correspond to sites of synthesis of enkephalins, including the caudate-putamen, the nucleus accumbens, the olfactory cortex, the hypothalamus, the brainstem and the granular layer of the cerebellum. The presence of the PPA mRNA in the normal rat adrenal medulla shows transcription of the PPA gene in such cells despite the absence of enkephalin immunoreactivity in them. These results demonstrate in situ hybridization as an efficient technique to detect the site of synthesis of PPA.

Immunocytochemical localization of proenkephalin-derived peptides in the central nervous system of the rat

Most of the early studies on the immunohistochemical distribution of enkephalin pentapeptide-like immunoreactivity used antisera that stained both proenkephalin- and prodynorphin-containing neurons. The present study used the peroxidase-antiperoxidase method, thick Vibratome sections and antisera specific for the carboxyl termini of [Met]enkephalin, [Met]enkephalyl-Arg6-Phe7, [Met]enkephalyl-Arg6-Gly7-Leu8, and metorphamide and for BAM 22P in order to obtain a detailed description of the distribution of authentic proenkephalin-containing perikarya and nerve processes. The peroxidase-antiperoxidase reaction product was intensified by the selective deposition of silver crystals in order to display the morphology of proenkephalin-containing neurons with great fidelity. The results indicate that the magnocellular perikarya in the supraoptic and paraventricular nuclei contain prodynorphin rather than proenkephalin as had been suggested by earlier investigators. The coarse fibers in the internal zone of the median eminence and the granule cell-mossy fiber pathway in the hippocampus also contain prodynorphin rather than proenkephalin. The number of proenkephalin-containing perikarya and/or the density of proenkephalin-containing nerve terminals in several other areas of the brain, e.g. the substantia nigra, the central amygdaloid nucleus, the periaqueductal gray and the parabrachial nuclei, were overestimated by earlier investigators. The distribution of authentic proenkephalin-containing perikarya and nerve processes is, despite these errors, similar to the distribution of enkephalin pentapeptide-like immunoreactivity described by earlier investigators. Proenkephalin-containing perikarya were identified for the first time in the medial and lateral habenular nuclei of the adult rat. Antisera specific for [Met]enkephalin, [Met]enkephalyl-Arg6-Phe7, [Met]enkephalyl-Arg6-Gly7-Leu8 and BAM 22P stain perikarya and nerve terminals with a similar distribution. The metorphamide antiserum also stains the same perikarya and nerve terminals; however, it also stains magnocellular perikarya in the zona incerta and the lateral hypothalamus that are not stained by any of the other proenkephalin-specific antisera.

In situ hybridization histochemistry for the analysis of gene expression in the endocrine and central nervous system tissues: a 3-year experience

We report our experience in development of the in situ hybridization (ISH) procedure to detect messenger RNAs (mRNAs) coding for various molecules involved in endocrine glands and central nervous system activity, including mRNAs coding for endorphin precursors [preproenkephalin A (PPA), pro-opiocortin (POMC)], vasopressin, and transferrin. Various conditions of fixation and handling of the tissues were tested to establish optimal parameters for mRNA detection. Double-stranded DNA probes labeled by nick translation, synthetic oligonucleotides labeled at their 5' end, as well as single-stranded RNA probes were used, after incorporation of 32P- or 35S-labeled nucleotides. Specific requirements for efficient and reproducible ISH investigations are discussed. Cells expressing the PPA gene in the adrenal medulla and in the brain were detected by ISH. The results show that ISH is as sensitive as immunohistochemistry in detecting peptide-producing cells in the adrenal and that it allows detection of PPA cell bodies in brain in conditions in which they are inconstantly detected by immunohistochemistry. Unilateral destruction of substantia nigra provokes a dramatic decrease in the number of neurons expressing the PPA gene in the contralateral striatum. Cells expressing the POMC gene were detected in the pituitary of various species including man and in the rat arcuate nucleus. Neurons containing vasopressin mRNA were visualized in the supraoptic paraventricular and suprachiasmatic nucleus of the adult rat by using a synthetic oligonucleotide probe. Transferrin gene expression was shown in the central nervous system of the rat brain in two cell populations, the oligodendrocytes and the epithelial cells of the choroid plexus, by demonstration of simultaneous presence in them of transferrin immunoreactivity together with transferrin mRNA. These results show that the ISH procedure is a technique that can be routinely used to investigate gene transcription anatomically in complex heterocellular tissues such as the endocrine glands and the nervous system.

Distribution of enkephalin-immunoreactive neurons in the forebrain and upper brainstem of the squirrel monkey

The distribution of enkephalin-immunoreactive neuronal profiles in the forebrain and upper brainstem of the squirrel monkey (Saimiri sciureus) was studied by means of the indirect immunofluorescence method. Numerous enkephalin-immunoreactive cell bodies and fibers were disclosed in various regions including cerebral cortex, hippocampus, caudate nucleus, putamen, nucleus accumbens, septal area, olfactory tubercle, substantia innominata, amygdala, various hypothalamic and thalamic nuclei, periaqueductal gray, midbrain reticular formation and interpeduncular nucleus. Some of the highest concentrations of enkephalin-positive fibers in the squirrel monkey brain were found in the external segment of the globus pallidus, the outer layer of the median eminence, and in the pars reticulata of the substantia nigra. Overall, the pattern of distribution of the enkephalin-immunoreactive cell bodies and fibers in the forebrain and upper brainstem of the squirrel monkey is similar to that found in the rat, except that the density of positive neuronal profiles in the entire forebrain appears much higher in monkey than in rat. Furthermore, the very dense network of enkephalin-immunoreactive fibers disclosed in the substantia nigra pars reticulata of monkey appears to be lacking in rat.

A pharmacological study on respiratory rhythm in the isolated brainstem-spinal cord preparation of the newborn rat

An in vitro brainstem-spinal cord preparation of the newborn rat was used to examine the effects of neurotransmitters and transmitter candidates on respiratory frequency. Spontaneous periodic depolarization of the spinal ventral roots of the 4th or 5th cervical segment was observed at a frequency of 5-15 min-1 constantly for more than 5 h. The frequency of this depolarization was monitored as an index of the respiratory frequency. An elevation of the concentration of Ca2+ or Mg2+ caused a decrease in the respiratory frequency, whereas an elevation of K+ concentration caused an increase. The frequency was also increased by a reduction of pH. The highest frequency was observed at 27-28 degrees C. Dopamine, 5-hydroxytryptamine, histamine, acetylcholine, glutamic acid, substance P, and thyrotropin releasing hormone accelerated the respiratory frequency when applied by perfusion to the brainstem, whereas noradrenaline, gamma-aminobutyric acid, glycine, and [Met5] enkephalin and [Leu5] enkephalin slowed the frequency. Experiments with antagonists suggested that the stimulant effect of acetylcholine on respiratory frequency was mediated mainly by muscarinic receptors and the depressant effect of noradrenaline was mediated by alpha-adrenoceptors.

The cytoarchitecture, histochemistry and projections of the tuberomammillary nucleus in the rat

The normal morphology, efferent projections and possible neurotransmitter content of neurons in the tuberomammillary nucleus (caudal magnocellular nuclei of Bleier et al.) [Bleier, Cohn and Siggelkow (1979) In Anatomy of the Hypothalamus, Vol. 1, pp. 137-220] have been examined in the adult male rat. In Nissl-stained sections, the nucleus can be divided into a dorsomedial, ventral and diffuse part, each of which consists of large, darkly stained neurons cradling the mammillary body. The ventral part is by far the largest and consists of some 2500 neurons on each side of the brain. Immunohistochemical studies indicate that a majority of the large neurons in all three parts of the nucleus stain with antisera against glutamate decarboxylase and [Met]enkephalyl-Arg6-Phe7 heptapeptide and that a smaller subset of these neurons (about 10%) also stain with an antiserum against substance P. Single injections of retrogradely transported fluorescent tracers were made into 18 different sites in 86 animals and the results indicate that all three parts of the tuberomammillary nucleus on one side of the brain send fibers to or through various parts of the neocortex, hippocampal formation, amygdala, basal ganglia, thalamus, superior colliculus and cerebellum on both sides of the brain and that the projection neurons are not organized in a highly topographic way. Injections of two different fluorescent tracers in the same animal indicate that individual neurons in the nucleus may give rise to both ascending and descending projections, as well as projections to widely divergent parts of the forebrain. Together with previous results, this evidence suggests that the tuberomammillary nucleus has widespread projections to the numerous brain structure located in the forebrain and in the caudal medulla (it may not project to the spinal cord), and that its axons may release a mixture of neuroactive substances including gamma-amino butyrate and several peptides. Although its functional significance remains to be investigated, morphological evidence suggests that the tuberomammillary nucleus may constitute one of a series of neurotransmitter-specific cell groups in the brainstem and basal forebrain with diffuse efferent projections that may be involved in the modulation of attention or behavioral state, rather than the processing of specific sensory or motor information.

Central somatostatin systems revealed with monoclonal antibodies

The distribution of central neurons displaying somatostatin immunoreactivity was studied using three monoclonal antibodies to cyclic somatostatin. The sensitive ABC immunoperoxidase technique was employed. A large number of positive cell groups including many previously undescribed populations were detected throughout the brain and spinal cord. Telencephalic somatostatin neurons included periglomerular cells in the olfactory bulb, mitral cells in the accessory olfactory bulb, and multipolar cells in the anterior olfactory nuclei, neocortex, amygdala, hippocampus, lateral septum, striatum, and nucleus accumbens. Within the hypothalamus, positive neurons were found in the periventricular, suprachiasmatic, and arcuate nuclei, and throughout the anterior and lateral hypothalamus. The entopeduncular nucleus and zona incerta contained many positive neurons, and the lateral habenula had a dense terminal field suggesting a pallidohabenula somatostatin pathway. Somatostatin neurons were also found in association with many sensory systems. Positive cells were present in the superior and inferior colliculi, the ventral cochlear nuclei, the ventral nucleus of the lateral lemniscus, nucleus cuneatus, nucleus gracilus, and the substantia gelatinosa. Various cerebellar circuits also displayed somatostatin immunoreactivity. Golgi cells throughout the cerebellar cortex were intensely stained, and some Purkinje cells in the paraflocculus also showed a positive reaction. Positive fibers were present in the granular layer and large varicose fibers were present in the inferior cerebellar peduncle. Many nuclei known to project to the cerebellum, including the nucleus reticularis tegmenti pontis, the medial accessory inferior olive, the nucleus prepositus hypoglossi, and many areas of the reticular formation contained positive neurons. These studies demonstrate that these new monoclonal antibodies are of great value for the study of central somatostatin systems. Previously described somatostatin systems are readily detected with these antibodies, and in addition, many otherwise unrecognized somatostatin cell groups have been discovered.

Release of proenkephalin-derived opioid peptides from rat striatum in vitro and their rapid degradation

In a previous paper we demonstrated that the heptapeptide [Met]enkephalyl-Arg6-Phe7 was released from rat striatal slices by high K+ concentration and rapidly degraded by peptidases, even in the presence of the neutral endopeptidase 24.11 ("enkephalinase")-inhibitor, thiorphan (0.1 microM), the angiotensin-converting enzyme inhibitor, captopril (1 microM), and the aminopeptidase inhibitor, bestatin (20 microM). In this study the pattern of degradation of exogenous [3H]heptapeptide by rat striatal slices has been studied. The angiotensin-converting enzyme and aminopeptidase(s) were partly responsible for this degradation. In addition an enzymatic activity that cleaved the Phe4-Met5 bond was involved in the degradation of the heptapeptide by striatal slices. This activity was inhibited by the dipeptide Leu-Arg (1 mM) and the tripeptide Leu-Arg-Leu (1 mM). The simultaneous presence of thiorphan (0.1 microM), captopril (1 microM), bestatin (20 microM) and Leu-Arg (1 mM) almost completely inhibited the degradation of [3H]heptapeptide by striatal slices. In the presence of these peptidase inhibitors a concomitant release of [Met]enkephalin, the heptapeptide [Met]enkephalyl-Arg6-Phe7 and the octapeptide [Met]enkephalyl-Arg6-Gly7-Leu8 was evoked by KCl or veratridine. The K+-evoked release was by a Ca2+-dependent mechanism and the release evoked by veratridine was blocked by tetrodotoxin. In both cases the ratio of [Met]enkephalin to heptapeptide amounts released was close to that found in their common precursor, proenkephalin. Thus the enkephalinergic neuron appears to be capable of synthesizing, from a unique precursor, four different putative opioid neurotransmitters, namely [Met]enkephalin, [Leu]enkephalin, the heptapeptide [Met]enkephalyl-Arg6-Phe7 and the octapeptide [Met]enkephalyl-Arg6-Gly7-Leu8, to store these peptides and to release them upon depolarization.

Evidence for synenkephalin-like immunoreactivity in pontobulbar monoaminergic neurons of the cat

Using indirect immunofluorescence, evidence that enkephalin- and synenkephalin-like-immunoreactivities are colocalized within numerous monoaminergic neurons of the cat pontobulbar formation is presented. The colocalization concerns most catecholaminergic cell bodies in the locus coeruleus region and numerous serotoninergic cell bodies in the raphe nuclei. Synenkephalin is the 1-70 N-terminal region of the bovine adrenal medulla proenkephalin. Therefore, the proenkephalin (or a related) system seems to represent the biosynthetic pathway for the enkephalins immunodetected within these monoaminergic neurons.

An enkephalinergic projection from the hypothalamic paraventricular nucleus to the hypothalamic ventromedial nucleus of the rat: an experimental immunohistochemical study

The distribution and origins of enkephalin-like immunoreactive (ENK-IR) fibers in the nucleus ventromedialis hypothalami (vm) of the rat were examined using immunohistochemistry. A dense plexus was evenly distributed in the vm with no regional differences. A group of ENK-IR neurons was concentrated in the ventrolateral portion of the vm. The destruction of the hypothalamic paraventricular nucleus (pv) which contained numerous ENK-IR neurons, resulted in a marked decrease in ENK-IR fibers in the vm on the operated side. In addition, the destruction of the magnocellular portion of the pv, while leaving most of parvocellular portion intact, failed to substantially decrease the ENK-IR fibers in the vm, suggesting that these fibers originate from ENK-IR neurons located in the parvocellular portion of the pv. The present study further showed that the axons of these neurons first proceeded laterally to the perifornical area, next ran ventrolaterally to the ventrolateral portion of the anterior hypothalamic nucleus and finally turned medially to the vm.

Pro-enkephalin peptides possessing Met-enkephalin-Arg6-Gly7-Leu8-immunoreactivity in rat CSF, striatum and adrenal gland

Cerebrospinal fluid (CSF) taken from rats implanted with chronic cisternal cannulae and extracts prepared from rat adrenal gland and striatum were subjected to Sephadex G-50 chromatography and HPLC. Fractions were monitored using specific radioimmunoassays (RIA) for the pentapeptide methionine enkephalin (Met-Enk) and methionine enkephalin-Arg6-Gly7-Leu8 (Met-EnkRGL). In rat CSF, striatum and adrenal gland, three Met-EnkRGL-immunoreactive (IR) peaks of Mrs 8000, 5000 and 1000 daltons were detected. The same peaks were also found to possess Met-Enk-immunoreactivity after enzyme digestion of Sephadex G-50 fractions with trypsin and carboxypeptidase B (CPB), suggesting their derivation from proenkephalin. HPLC of the 8K and 5K peaks on a column of Ultrapore RPSC showed them to elute discretely with similar retention times, indicative of hydrophobic peptides of large molecular weight. Their similar hydrophobicities yet significant separation during gel filtration would suggest that the 8K and 5K peptides are structurally closely related yet different with respect to their molecular weights. HPLC of the small molecular weight material from rat striatum and adrenal gland revealed the presence of Met-EnkRGL and Met-EnkRGL sulphoxide in both tissues. In rat striatum Met-Enk and its sulphoxide were also detected. The oxidised pentapeptide was found to be present in rat CSF, together with two unidentified small molecular weight Met-Enk-IR peaks detected without prior enzyme digestion of fractions. The small molecular weight Met-EnkRGL-IR material in rat CSF was found to be comprised of two unknown peptides which were less hydrophobic than Met-EnkRGL and its sulphoxide derivative.

Distribution of immunoreactive Met-enkephalin-Arg6-Gly7-Leu8 and Leu-enkephalin in discrete regions of the rat brain

The distribution of immunoreactive (ir) leucine-enkephalin (LE) and ir-methionine-enkephalin-Arg-Gly-Leu (ME-RGL) in 101 microdissected rat brain and spinal cord regions was determined using specific and sensitive radioimmunoassays. The highest concentrations of LE and ME-RGL were measured in globus pallidus (5190 and 4378.8 fmol/mg protein, respectively). Very high concentrations of LE and ME-RGL (greater than 750 fmol/mg protein) were found in the central amygdaloid nucleus, anterior hypothalamic nucleus, lateral preoptic area, nucleus of the solitary tract (medial and commissural parts), bed nucleus of stria terminalis, dorsomedial nucleus, parabrachial nuclei, periaqueductal gray and motor hypoglossal nucleus. Very high concentrations of ME-RGL were found in 14 additional brain regions including medial preoptic area, area postrema, nucleus ambiguus, periventricular nucleus, ventromedial nucleus, interpeduncular nucleus, paraventricular, arcuate and others. High concentrations of LE (between 500 and 750 fmol/mg protein) were found in 15 brain areas, among them the periventricular nucleus, medial preoptic area, suprachiasmatic nucleus, dorsal premamillary nucleus, ventromedial nucleus, arcuate nucleus, nucleus ambiguus, locus coeruleus, substantia nigra. High concentrations of ME-RGL were measured in 13 brain areas including the suprachiasmatic nucleus, lateral septal nucleus, raphe magnus, motor facial nucleus, lateral amygdaloid nucleus, sensory trigeminal nucleus, nucleus accumbens, caudate-putamen. Moderate concentrations of LE (between 250 and 500 fmol/mg) were found in 46 brain areas such as the lateral septal nucleus, nucleus accumbens, caudate-putamen, several amygdaloid nuclei, supraoptic nucleus, the perifornical nucleus, posterior hypothalamic nucleus, red nucleus. Moderate concentrations of ME-RGL were detected in 27 areas such as the median eminence, nuclei of the reticular formation, supraoptic nucleus, red nucleus and others.(ABSTRACT TRUNCATED AT 250 WORDS)

Electroconvulsive shock increases preproenkephalin messenger RNA abundance in rat hypothalamus

Daily administration of electroconvulsive shock (ECS) to rats for 10 days increased the content of [Met5]enkephalin in the hypothalamus and the striatum by 64% and 45%, respectively. The effect of ECS on the relative abundance of mRNA coding for the enkephalin precursor preproenkephalin was investigated. Analysis by cell-free translation of polyadenylylated RNA and immunoprecipitation of preproenkephalin revealed ECS-elicited increases of 79% and 14% in preproenkephalin mRNA activity in the hypothalamus and striatum, respectively. ECS treatment did not affect the general translational activity of total polyadenylylated RNA from these brain regions. A 32P-labeled probe prepared from a rat preproenkephalin cDNA clone hybridized with an apparently single species of polyadenylylated RNA of approximately equal to 1450 nucleotides from both hypothalamus and striatum. Dot-blot hybridization of polyadenylylated RNA with the rat probe indicated that ECS elicits a 76% increase in the preproenkephalin mRNA abundance in the hypothalamus and no significant change in the striatum. These results suggest that ECS treatment leads to enhanced biosynthesis of the enkephalin precursor in hypothalamic neurons.

Distribution and localization of regulatory peptides

A new group of modulatory substances present in both endocrine cells and central and peripheral nerves has been described in the past few years. These substances are biochemically recognized as peptides and their actions affect many bodily functions. They are now widely known as regulatory peptides. The development of new immunocytochemical techniques, closely allied to radioimmunoassay, has disclosed that the regulatory peptides are present either in cells or in nerves, in almost every tissue of the body. The presence of peptides (the classical hormones) in endocrine cells was already known at the beginning of the century, but the presence of similar substances in nerve fibers, where they probably act as neurotransmitters, is a recent and revolutionary discovery. More than 30 peptides (neuropeptides) have been found to be present in nerves, to which the term "peptidergic" has been applied, although it is now known that in certain cases a neuropeptide can be present in the same nerves as a classical neurotransmitter, for example acetylcholine with VIP, or noradrenaline with NPY. Little is known about the physiological role of these neuropeptides. It is not yet fully accepted that they act as neurotransmitters although there is strong evidence for this, particularly in the case of substance P and VIP. The investigation of the regulatory peptides is now in an initial phase. The involvement of new disciplines, such as molecular biology, in this field is producing new and very exciting discoveries, including the isolation of novel peptides and precursors, the study of which will further contribute to the understanding of the basic control mechanisms.

Chromogranin immunoreactivity in the central nervous system. Immunochemical characterisation, distribution and relationship to catecholamine and enkephalin pathways

Chromogranin A, the major soluble protein of the chromaffin granules, was isolated from bovine adrenals and used for immunization of rabbits. Chromogranin (CHR) immunoreactivity was studied by immunochemical and immunohistochemical methods in the adrenal, pituitary, brain and spinal cord of cattle, sheep, rats and guinea pigs using two antisera neither of which cross-reacted with dopamine beta-hydroxylase. Detailed studies were done using tissues from sheep only because very weak immunoreaction was obtained in tissues from the latter two species. Immunoblots of soluble proteins separated by two-dimensional polyacrylamide gel electrophoresis showed that the sera recognized a family of polypeptides in the adrenal which differed in size, but had almost identical isoelectric points. The patterns of immunoreactive proteins in extracts from the adrenal and pituitary were similar. Only two bands corresponding to the major high molecular weight bands in adrenal could be detected in the hippocampus which appeared to have a lower concentration of antigen. Other brain areas also showed two major immunoreactive proteins, one with a molecular weight similar to chromogranin A, and one smaller. Adrenal chromaffin cells, peripheral noradrenergic nerve axons and terminals in the pineal gland, a proportion of the anterior pituitary cells and the neurosecretory terminals of the posterior pituitary were strongly immunoreactive. In addition, CHR-immunoreactivity was widely distributed in the brain and spinal cord. The reactivity was readily visible in some nerve cell bodies and in well-defined pathways and terminal fibre networks. There were neurons whose perikarya were intensely stained but whose terminal projections appeared to be negative, while in other cases, the terminals appeared rich in CHR, while the perikarya were barely stained. All chromogranin immunoreactivity was abolished by absorption of the sera with a lysate from the chromaffin granules, but was not affected by absorption with Met- or Leu-enkephalin, dynorphin1-17, Met-enkephalin-Arg6-Phe7 or BAM-22P. Electron microscopic experiments revealed that the CHR-reaction in cell bodies was almost exclusively confined to the Golgi apparatus, while in synaptic boutons it was found in large dense-cored vesicles common to many types of terminals. In the hippocampal mossy fibre terminals, the immunoreactive granulated vesicles sometimes appeared to have fused with the plasma membrane of the boutons suggesting that the CHR was being secreted by exocytosis. The CHR-immunoreactivity was found to overlap partially with the distribution of many other neuroactive substances.(ABSTRACT TRUNCATED AT 400 WORDS)

A study of afferent projections to the rat interpeduncular nucleus

Forebrain and brainstem afferents projecting to the interpeduncular nucleus (IPN) have been demonstrated in male rats by retrograde transport of fluorescent dye, "fast blue," microinjected in IPN, followed by intraventricular colchicine 48 hr prior to perfusion. The most intensely labeled cells projecting to IPN were concentrated throughout the entire rostrocaudal extent of the medial habenular nuclei. A small number of labeled medial habenular cells located dorsomedially also revealed SP immunofluorescence. Additional forebrain afferents originate from septal, hypothalamic and mammillary nuclei. Of brainstem afferents projecting to IPN, the most intensely labeled neurons were present in a circumscribed region overlying the dorsal aspect of the dorsal tegmental nucleus, an area described in the cat as the nucleus incertus [5], and which we now suggest is present in the rat. Many labeled cells in the medial aspect of this nucleus also revealed L-ENK immunofluorescence. Additional brainstem afferents include the raphe, dorsolateral tegmental nuclei and locus coeruleus. This study demonstrates both forebrain and brainstem afferents projecting to IPN and reveals an SP and L-ENK projection from the medial habenula and nucleus incertus, respectively.

Effects of chemical and surgical lesions on levels of chromatographically identified enkephalin-like peptides in rat hippocampus

The present study quantitates the content of Met- and Leu-enkephalin in the rat hippocampus, and provides information on the localization of the enkephalins within the hippocampal neuronal circuitry. Several enkephalins were identified in rat hippocampus, two of which are shown to be Met- and Leu-enkephalin. The levels of these enkephalins, and of other unidentified enkephalin-related peptides, were not depleted by intrahippocampal colchicine, which destroyed the great majority of the hippocampal granule cells and the associated mossy fiber pathway. Entorhinal cortical lesions ablating the perforant pathway input to the hippocampus also did not significantly lower enkephalin levels in the hippocampus. Unilateral fimbrial transection caused a significant bilateral increase in both Met- and Leu-enkephalin levels. This may result from loss of a stimulatory input to putative enkephalin containing interneurons within the hippocampus. The extents of all lesions were verified histologically in hippocampi used for biochemical analysis. No evidence was seen for the presence of enkephalins in the perforant pathway, nor in nerve fibers in the fimbria/fornix, which provide the other main source of hippocampal efferents. The enkephalins are likely to be intrinsic to the hippocampus, in which neuronal cell bodies containing enkephalin-like immunoreactivity have been extensively reported.

Distribution of substance P and enkephalin-like immunoreactivity in the substantia nigra of rat, cat and monkey

A comparative study of the distribution of substance P (SP) and enkephalin (ENK) immunoreactivity in the substantia nigra (SN) of the rat, cat and squirrel monkey (Saimiri sciureus) was undertaken by means of the indirect immunofluorescence technique. In the rat a dense neuronal network composed of fine fibers displaying SP immunoreactivity is uniformely distributed throughout the rostrocaudal extent of the substantia nigra pars reticulata (SNr) and in the ventral part of substantia nigra pars compacta (SNc). Some coarse SP-positive fibers also occur in SNc. In addition, ENK-immunoreactive fibers are scattered amongst SNc neurons but abound particularly in the caudolateral part of SNr. In cat innumerable fine SP-positive fibers are distributed in SNr according to a pattern similar to that found in rat. ENK-immunoreactive fine fibers are densely packed in the ventromedial part of SNr whereas coarse ENK fibers are scattered in both SNc and SNr but abound particularly in the caudolateral portion of SNr. In monkey fine SP and ENK-immunoreactive fibers occur in very large number in SNr. These two types of fibers are distributed according to a similar but strikingly complex and heterogeneous pattern. In addition, coarse fibers displaying either SP or ENK immunoreactivity are scattered amongst the SNc neurons in monkey. These findings reveal that SP immunoreactive fibers are present in large number and are distributed according to a somewhat similar pattern in rat, cat and monkey. In contrast, the number of ENK-positive fibers and the complexity of their organizational feature in SN increase strikingly from rodent to primate.

Ontogeny of dynorphin-like immunoreactivity in the hippocampal formation of the rat

Light microscopic immunocytochemical techniques were used to analyze the ontogeny of dynorphin (A)-like immunoreactivity (DLI) in the hippocampal formation of the Sprague-Dawley rat. For comparison purposes, alternate sections of the same brains were processed for the localization of methionine enkephalin-like immunoreactivity (ELI). DLI was first detectable in CA3a stratum lucidum and the suprapyramidal hilus on postnatal day (P) 6. On P7, DLI was evenly present throughout the full extent of the mossy fiber system. From P8 to P19, DLI progressively increased in intensity and could be localized in the fine axons and spherical swellings. The mossy fiber system and occasional perikarya superficial to stratum granulosum were the only hippocampal elements that exhibited DLI. In corroboration with earlier results, stratum lucidum ELI was first detected within large spherical bouton-like swellings on P13. From these data it is concluded that DLI appears in morphologically immature mossy fibers soon after they reach their target fields. In contrast, enkephalin is first detected within morphologically elaborated mossy fiber boutons well after the establishment of functional synapses.

Evidence for different patterns of post-translational processing of pro-enkephalin in the bovine adrenal, colon and striatum indicated by radioimmunoassay using region-specific antisera to Met-Enk-Arg6-Phe7 and Met-Enk-Arg6-Gly7-Leu8

Specific antisera to two opioid peptides, Met-Enk-Arg6-Phe7 and Met-Enk-Arg6-Gly7-Leu8, were used in radioimmunoassay to study molecular forms in extracts of bovine adrenal, striatum and colon. The antisera to Met-Enk-Arg6-Phe7 and Met-Enk-Arg6-Gly7-Leu8 were each highly specific for the C-terminus of their respective haptens and showed less than 1% cross-reactivity with related enkephalins and their variants. In adrenal extracts, gel filtration on Sephadex G-50 indicated N-terminally extended forms of Met-Enk-Arg6-Phe7 and Met-Enk-Arg6-Gly7-Leu8 as the predominating immunoreactive species, whereas in the striatum and colon the main immunoreactive forms were compatible with the hepta- and octapeptides. The results suggest different patterns of post-translational processing of precursors in the adrenal medulla compared with striatal and colonic neurones.

Distribution of NT-IR perikarya in the brain of the guinea pig with special reference to cardiovascular centers in the medulla oblongata

The occurrence and distribution of neurotensin-immunoreactive (NT-IR) perikarya was studied in the central nervous system of the guinea pig using a newly raised antibody (KN 1). Numerous NT-IR perikarya were found in the nuclei amygdaloidei, nuclei septi interventriculare, hypothalamus, nucleus parafascicularis thalami, substantia grisea centralis mesencephali, ventral medulla oblongata, nucleus solitarius and spinal cord. The distribution of NT-IR perikarya was similar to that previously described in the rat and monkey. In the gyrus cinguli, hippocampus and nucleus olfactorius, though, no NT-IR neurons were detected in this investigation. Additional immunoreactive perikarya, however, were observed in areas of the ventral medulla oblongata, namely in the nucleus paragigantocellularis, nucleus retrofacialis and nucleus raphe obscurus. The relevance of the NT-IR perikarya within the ventral medulla oblongata is discussed with respect to other neuropeptides, which are found in this area, and to cardiovascular regulation.

Effect of dopaminergic agents on levels of dynorphin1-8 in rat striatum

In this study, the possibility that striatal dynorphin1-8 levels would be altered by either acute or chronic treatment with dopaminergic agonists or antagonists is examined. Animals were treated chronically (3 weeks) with daily injections of d-amphetamine, phencyclidine or haloperidol. For the acute studies, animals were given a single dose of either d-amphetamine or haloperidol. Dynorphin1-8 levels were estimated using a radioimmunoassay. Only chronic treatment with d-amphetamine has any effect on dynorphin1-8 levels. Following 3 weeks of chronic d-amphetamine, the level of dynorphin1-8 increased in 2 separate experiments. Acute d-amphetamine or haloperidol treatment or chronic haloperidol or phencyclidine treatment had no effect on striatal dynorphin1-8 levels. However, chronic (but not acute) d-amphetamine administration does produce a small increase in striatal dynorphin1-8 levels.

Relative contents and concomitant release of prodynorphin/neoendorphin-derived peptides in rat hippocampus

The contents and molecular forms of five different prodynorphin-derived opioid peptides were compared in extracts of rat hippocampus by radioimmunoassay after C18-HPLC resolution. Dynorphin (Dyn) A(1-17) immunoreactivity (ir) and Dyn B-ir were heterogeneous in form; Dyn A(1-8)-ir, alpha-neoendorphin (alpha neo)-ir and beta-neoendorphin (beta neo)-ir each eluted as single homogeneous peaks of immunoreactivity. The fraction of immunoreactivity having the same retention as the appropriate synthetic standard was used to estimate the actual hippocampal content of each peptide. Comparison of these values showed that the concentrations of Dyn B, alpha neo, and Dyn A(1-8) were nearly equal, whereas both Dyn A(1-17) and beta neo were 1/5th to 1/10th the value of the other three. Calcium-dependent K+-stimulated release of these prodynorphin-derived opioids from hippocampal slices was detected. The stimulated rates of release were highest for Dyn B-ir followed by alpha neo-ir, then beta neo-ir and Dyn A(1-8)-ir with Dyn A(1-17)-ir lowest. The relative rates of stimulated release were in agreement with the relative proportions of peptide present within the tissue. This evidence of the presence and release of these opioid peptides considerably strengthens the hypothesis that this family of endogenous opioids plays a neurotransmitter role in the hippocampus.