Enkephalin-like Immunoreactivity Research Articles

Enkephalin-like immunoreactivity in the chick brainstem: possible relation to the cochlear efferent system

Mammalian lateral olivocochlear (LOC) neurons that are immunoreactive for choline acetyltransferase (ChAT) are also immunoreactive for enkephalin (Enk). To determine whether cochlear efferent neurons in birds might also contain Enk-like immunoreactivity (Enk-LI), we studied the auditory brainstem of the domestic chicken using antisera to ChAT, leucine-enkephalin (L-Enk) and methionine-enkephalin (M-Enk). Enk-LI terminals are found around, but not within, the superior olivary nucleus (SO) and the nucleus of the lateral lemniscus, pars intermedia (LLi). A moderate concentration of Enk-LI terminals is found ventromedial to the ventral facial nucleus (VIIv) where the ventrolateral group of ChAT-I cochlear efferent neurons is located. After colchicine injections into the lateral ventricle, a population of intensely stained Enk-LI perikarya was found in the nucleus of the lateral lemniscus, pars ventralis (LLv) with scattered cells in the LLi and the nucleus subceruleus ventralis (SCv). The distribution of Enk-LI and ChAT-I somata, however, never overlapped, even in adjacent sections. Thus, in the chick, Enk-LI perikarya are not distributed in areas where cochlear efferent neurons are found. Instead, a dense concentration of Enk-I terminals can be found in areas containing ChAT-I cochlear efferent neurons. The source of these enkephalinergic terminals may be a population of Enk-LI cells in the LLv.

Distribution of GABAA receptor alpha 1 subunit-like immunoreactivity in comparison with that of enkephalin and substance P in the rat forebrain.

The gamma-aminobutyric acid-A receptor consists of several subunits. In this immunohistochemical study we investigated the regional distribution of the alpha 1 subunit with an antibody directed against a specific amino acid sequence (1-9) of the (1-9) of the alpha 1 subunit. We compared the distribution pattern of the alpha 1 subunit-like immunoreactivity with that of substance P- and enkephalin-like immunoreactivities in adjacent sections of the rat forebrain. alpha 1 subunit-like immunoreactivity appeared in the form of varicosities and fibers. A band-like terminal staining pattern (woolly fibers) that has been shown by others for substance P- and enkephalin-like immunoreactivity is also observed for alpha 1 subunit-like immunoreactivity. In contrast to substance P and enkephalin, numerous alpha 1 subunit-like immunoreactive perikarya were found. The highest density of alpha 1 subunit-like immunoreactive fibers and perikarya was found in the pallidal areas and the substantia nigra pars reticulata whereas the nucleus accumbens and the caudate putamen displayed a low density. alpha 1 subunit-like immunoreactive neurons resembled typical pallidal neurons. Some of these neurons were pericellularly stained with enkephalin-like immunoreactive varicosities in the dorsal pallidum. The distribution pattern of alpha 1 subunit-like immunoreactivity reflects a partial overlap with the substance P and enkephalin system although a differential distribution to each of these peptides was observed for cell bodies, fibers, and axon terminals.

Metabolic profile of opioid peptides differs in the hippocampus and striatum of seizure-susceptible E1 mice

We previously suggested that a deficit of anticonvulsant endogenous methionine enkephalin, in the cerebral cortex, septal area, hippocampus, and striatum of seizure-susceptible El mice plays a role in the pathogenesis of seizures. To determine whether a hypofunction of enkephalinergic neuron may be due to metabolic abnormalities of opioid peptides in the El mouse brain, we measured methionine enkephalin-like immunoreactivity (ME-LI) of 50 fractions eluted by high performance liquid chromatography obtained from those four regions of the brain of El and seizure-nonsusceptible ddY mice (the mother strain of El mice). We observed the same ME-LI patterns of 50 fractions in the cerebral cortex and septal area in El and ddY mice, whereas exhibited differing ME-LI patterns in the hippocampus and striatum in the two stains. Different ME-LI patterns may imply the difference in the metabolic profile of opioid peptides. Thus, an abnormal metabolism of opioid peptides in the hippocampus and striatum of the El mouse may be involved in the pathogenesis of seizures.

Increase in enkephalin-like immunoreactivity in hippocampi of adults with generalized epilepsy

The changes of opioid peptide reactivity in seizure activity have been well studied in animals. Increased enkephalin and dynorphin immunoreactivity in the hippocampi of animals are interpreted as the result of seizure induced mossy fibre sprouting. We studied the hippocampi of six patients with a history of long-standing grand mal seizures and six age-matched control patients with no history of epilepsy or neurologic disease, using frozen sections which were immunostained with antibodies against Leu-enkephalin and Met-enkephalin. The staining intensity in the CA3, CA4 and internal molecular layer of the dentate fascia in each case was quantified using optical densitometry image analysis. The CA3 and CA4 of the epileptic hippocampi showed highly significant increase in Leu-enkephalin-like immunoreactivity compared to the controls (P < 0.005) while the inner molecular layer showed only significant increase (P < 0.05). Met-Enkephalin-like immunoreactivity was only significantly increased in CA4 of the epileptic hippocampi (P < 0.05).

A role for the enkephalin-immunoreactive amacrine cells of the chicken retina in adaptation to light and dark.

The functional state of the amacrine cells which contain enkephalin-, neurotensin- and somatostatin-like immunoreactivity of the chicken retina was monitored by measuring the rate of change in the levels of [Leu]enkephalin-like immunoreactivity in the retina. Dark-adapted birds were exposed to lights of different intensities for 12 h. At light levels of < or = 0.03 microW/cm2, the ENSLI amacrine cells were highly active but, by 0.08 microW/cm2, they reached a state of maximum inactivation. Thus, the ENSLI amacrine cells act as flip-flop devices, inactivated by critical levels of light, which correspond to those which inactivate pineal melatonin synthesis. They may, therefore, be involved in retinal pathways which signal the difference between day and night.

Endogenous dopamine inhibits the release of enkephalin-like immunoreactivity from amacrine cells of the chicken retina in the light

The activity of the enkephalin-immunoreactive (ENSLI) amacrine cells of the chicken retina is low in the light and high in the dark, resulting in parallel increases and decreases in the levels of the enkephalins. In vivo, the selective dopaminergic D 1 antagonist SCH23390 increased the activity of the ENSLI amacrine cells in the light (ED 50; 20 pmol), but had a much lesser effect in the dark, whereas the selective dopaminergic D 2 antagonist sulpiride had effects only at very high concentrations (ED 50; 39 nmol). In contrast, the non-selective dopamine agonist ADTN hardly affected the activity of the ENSLI amacrine cells in the light, but markedly reduced their activity in the dark. This pattern of effects suggests that dopamine actively inhibits the ENSLI amacrine cells in the light, but exerts much less inhibitory activity in the dark, consistent with the idea that dopamine is released during the exposure of the retina to light. Thus dopaminergic controls over the ENSLI amacrine cells appear to contribute to the light:dark differences in activity of the ENSLI amacrine cells. Results obtained on the dopaminergic control of enkephalin release in vitro were generally consistent with this model, except that ADTN appeared to stimulate the ENSLI amacrine cells in the dark.

Met5‐enkephalin is localized within axon terminals in the subfornical organ: Vascular contacts and interactions with neurons containing gamma‐aminobutyric acid

Met5-enkephalin inhibits sodium and water excretion and antagonizes the central actions of angiotensin II in subfornical organ of rat brain. We examined the ultrastructural basis for enkephalin modulation in this circumventricular region. Additionally, we examined the possibility that there might be cellular sites for functional interactions involving Met5-enkephalin and gamma-aminobutyric acid (GABA), a known inhibitory transmitter throughout the central nervous system. Met5-enkephalin and GABA were identified in single coronal sections through the subfornical organ using immunoperoxidase and silver-enhanced immunogold labeling methods, respectively. Enkephalin-like immunoreactivity was most prominently localized within axon terminals. These were distributed primarily in the central, highly vascular, regions of the subfornical organ. Enkephalin-labeled terminals were apposed to the basement membranes of fenestrated capillaries and also formed symmetric, inhibitory type synapses with neurons. In terminals associated with either blood vessels or neurons, the enkephalin immunoreactivity was enriched in large (80-150 nm) dense core vesicles. The immunoreactive vesicles were usually located within portions of the axon in close proximity to astrocytic processes. In contrast, smaller vesicles in the same terminals were more often aggregated near the basement membrane of the capillaries and the active zone of the synapse. The targets of enkephalin-immunoreactive terminals were either unlabeled or GABA-labeled dendrites of local neurons. Enkephalin was also co-localized with GABA in perikarya and in axon terminals. Terminals containing only GABA were far more abundant than those containing enkephalin or enkephalin and GABA. GABA-immunoreactive terminals formed symmetric synapses on unlabeled dendrites some of which also received convergent input from terminals containing enkephalin. Additionally, the enkephalin-immunoreactive terminals were closely apposed to GABA-labeled and unlabeled terminals. These results suggest sites for nonsynaptic release of Met5-enkephalin from dense core vesicles in contact with astrocytes near blood vessels and synaptic complexes in the rat subfornical organ. Moreover, the observed dual localization and pre- and postsynaptic associations between neurons containing Met5-enkephalin and GABA indicate that inhibitory effects of opioids in the subfornical organ may be mediated or potentiated by GABA.

Enkephalin‐positive and acetylcholinesterase‐positive patch systems in the superior colliculus have matching distributions but distinct developmental histories

Histochemical stains for acetylcholinesterase activity and enkephalin-like immunoreactivity both demonstrate a high degree of patterning in the superior colliculus, particularly in the intermediate and deep layers. Both markers occur predominantly in the neuropil of these layers, and both are principally distributed in distinct macroscopic compartments. We report here that patches of heightened acetylcholinesterase activity correspond to patches of high enkephalin-like immunoreactivity. The two markers thus delineate largely the same domain in the intermediate and deep layers. The most prominent zones of staining for enkephalin-like peptide and for acetylcholinesterase also coincided in the dorsolateral periaqueductal gray matter. These findings suggest a close interlocking of one or more acetylcholinesterase-containing systems with one or more pathways related to endogenous opioids in the superior colliculus. As the acetylcholinesterase expression in the patches is known to match in detail choline acetyltransferase expression, our results also suggest the possibility of local cholinergic-opiatergic interactions. In some sections, blood vessels associated with enkephalin-rich and acetylcholinesterase-rich patches extended beyond the colliculus into the periaqueductal gray matter, where they again became surrounded by dense fibrous labeling. This pattern suggests that neurohumoral signal exchange might occur through blood vessels even in a sensory-motor structure such as the colliculus. In a postnatal developmental series of kitten brains we found that enkephalin-like immunoreactivity was already distinctly compartmental in the intermediate layers at birth and continued to show this distribution throughout postnatal development. By contrast, acetylcholinesterase staining was nearly homogeneous at birth and became compartmental gradually during the first postnatal weeks. Thus, despite the eventual near coincidence of the enkephalin-rich and acetylcholinesterase-rich compartments of the superior colliculus, they mark systems that follow distinct programs of neurochemical development.

Peptidergic innervation of human sphincter of Oddi.

The innervation of the sphincter of Oddi (SO) has been extensively studied experimentally, but human studies have not been published, which is why this study was undertaken. Biopsies, taken by gastroscopy-biopsy forceps from duodenal epithelium of the papilla of Vater and from ampullary epithelium after sphincterotomy, did not demonstrate nerves and could not be used for studying SO innervation. Therefore SO specimens were obtained from brain-dead organ donors (N = 5) and from autopsies (N = 14). By staining with a myelin marker S-100, a rich network of nerves was demonstrated in SO. The occurrence of vasoactive intestinal polypeptide (VIP), peptide histidine-isoleucine (PHI) (or its immunologically similar human equivalent peptide histidine methioninamide, PHM), neuropeptide Y, calcitonin gene-related peptide (CGRP), galanin, substance P, enkephalin, bombesin, and somatostatin were studied by immunohistochemical technique. SO demonstrated immunoreactivity for VIP, PHI (PHM), neuropeptide Y, CGRP, galanin, somatostatin, substance P, and enkephalin, but no immunoreactivity was observed for bombesin. The SO immunoreactivity was similar in specimens from organ donors and from autopsies of victims of violence without pancreatobiliary diseases (N = 3) when the specimens were taken within 48 hr of death. Autopsy specimens of SO from subjects with gallstone disease (N = 5), recurrent pancreatitis (N = 3) or periampullary carcinoma (N = 3) also demonstrated similar immunoreactivity. We conclude that VIP-, PHI- (PHM-), neuropeptide Y-, CGRP-, galanin-, substance P-, somatostatin-, and enkephalin-like immunoreactivity occur in human SO. These neuropeptides may have role in the neural control of human SO function.

Effects of space flight stress on proopiomelanocortin, proenkephalin A, and tachykinin neuropeptidergic systems in the rat posterior pituitary

β-endorphin-like immunoreactivity (BE-li), methionine enkephalin-like immunoreactivity (ME-li), and substance P-like immunoreactivity (SP-li) were measured in the posterior pituitary of rats that experienced a 5-day space flight in a Space Shuttle. ME-li and SP-li were both significantly lower compared to the control rats. However, there was no difference in BE-li between flight and control rats. These data suggest that the space flight stress diminished the methionine enkephalin (ME) and substance P (SP) concentrations in the posterior pituitary without affecting the β-endorphin (BE) concentration. Thus, the proenkephalin A and tachykinin, but not proopiomelanocortin, neuropeptidergic systems in the posterior pituitary may respond to this type of unique stress.

Assay of Preproenkephalin A Processing Enzymes in Human Lumbar Cerebrospinal Fluid

Vmax and Km measurements have been obtained for endogenous peptidases that are important for methionine enkephalin (ME) homeostasis in humans. Those peptidases in human lumbar cerebrospinal fluid (CSF) act upon several synthetic biologically significant peptides that are also contained within the preproenkephalin Ahuman, 1-267 molecule. The amount of endogenous methionine enkephalin-like immunoreactivity (ME-li) in human lumbar CSF is 74.1 ± 5.7 fmol ME-li/ml CSF (n = 56; x ± SE). The kinetic parameters of the various enzymes that inactivate exogenous, synthetic methionine enkephalin (ME, YGGFM) and that also produce ME from two different portions of the preproenkephalin Ahuman, 1-267 precursor molecule were determined. The enzyme that inactivates synthetic ME to FM, and that correlates to the rate of decrease of ME, has a Vmax = 560 ± 43.3 nmol/ml/min and a Km = 4514 ± 373 μM (n = 56; x ± SE). Preproenkephalin Ahuman, 186-193 (PA = YGGFMRGL) was added to CSF samples to characterize those processing and converting enzymes that produce the ME pentapeptide. Vmax, as measured by the rate of the decrease of PA to produce YGGFMR, was 0.192 ± 0.038 nmol/ml/min and a Km of 513 ± 121 μM (n = 10; x ± SE). Similarly, a bovine analog to preproenkephalin Ahuman, 128-140 (PPEhuman, GSEILAKRYGGFM; PPEbovine, 125-137, GGEVLGKRYGGFM) was used to characterize that enzyme system that produces ME from an N-terminally extended ME peptide. That endopeptidase had a Vmax of 0.120 ± 0.048 nmol/ml/min with a Km of 734 ± 296 μM (n = 10). Those endogenous enzymes in human CSF may relate to the proopiomelanocortin convertase enzymes that contain the subtilisin-like catalytic domain.

Leu 5]enkephalin-like immunoreactive amacrine cells are under nicotinic excitatory control during darkness in chicken retina

Based on the principle that retinal levels of [Leu 5]enkephalin-like immunoreactivity (LELI) are set by the rate of release and thus reflect neural activity, we partially defined the dark-associated increase in excitatory control of LELI amacrine cells in chicken. Retinal levels of LELI were measured by radioimmunoassay (RIA). Intravitreal injection of cholinergic antagonists decreased the rate of depletion of LELI during the dark phase, suggesting the presence of cholinergic excitatory control of the LELI neurons. This cholinergic control involves nicotinic rather than muscarinic receptors, as tubocurarine appeared over 100 times more effective than atropine in inhibiting the decrease in retinal levels of LELI in the dark. (The ED 50s were estimated at 3.2 and 450 nmol, respectively.) The lack of effect of the antagonists when applied during the light phase, suggest that there is little cholinergic input to the LELI amacrine cells in the light. Superfusing isolated retinas with buffer containing tubocurarine (10 μM) decreased the efflux of LELI by 35%, compared to the spontaneous release during the dark. Atropine (10 μM) had no effect on the release of LELI, and pilocarpine (100 μM) increased the release of LELI from retinas superfused in the light by 20%. We conclude that, in addition to previously reported glycinergic and dopaminergic inhibition, the LELI amacrine cells receive cholinergic excitatory input. A shift in balance between glycinergic and dopaminergic inhibitory, and cholinergic excitatory control may underly the light-driven variation in activity of the LELI neurons in chicken retina.

Adrenal cortical and medullary responses to acetylcholine and vasoactive intestinal peptide in conscious calves.

1. Adrenal responses to intra-aortic infusions of acetylcholine and vasoactive intestinal peptide (VIP) have been investigated in functionally hypophysectomized calves given exogenous adrenocorticotrophic hormone (ACTH, 2 ng min-1 kg-1 I.V.). 2. Infusions of VIP at a dose of 0.13 micrograms min-1 kg-1 caused a small, but significant increase in adrenaline and noradrenaline output which was, however, far below the level recorded previously in response to acetylcholine (0.7 micrograms min-1 kg-1). In contrast, these doses of the two agonists produced closely similar rises in adrenal cortisol output. 3. The steroidogenic effects of acetylcholine and VIP were found to be strictly additive and no evidence of potentiation was obtained in relation to either cortical or medullary responses or in the case of any of the cardiovascular responses which were monitored. 4. Intra-aortic infusions of VIP, at a dose which produced a substantial increase in adrenal steroidogenesis (0.065 micrograms min-1 kg-1), had no effect on the output of catecholamines, enkephalin-like immunoreactivity or corticotrophin-releasing factor, either in the presence or absence of acetylcholine. 5. It is concluded that VIP is unlikely to modulate adrenal medullary responses to muscarinic stimulation in this species as it has been claimed to do in the rat and does not potentiate adrenal steroidogenesis in response to acetylcholine as it does to ACTH.

Output architecture of the primate putamen

The basal ganglia act through direct and indirect striatopallidal output pathways that have different effects on cortical activity. This division has been proposed to underlie the fundamental distinction between hyperkinetic and hypokinetic movement disorders such as Parkinson's disease and Huntington's disease. Evidence to date does not favor a relationship between this dual organization and the division of the striatum into striosome and matrix compartments. However, the possibility has been raised that the division of striatopallidal output paths reflects a compartmentalization of the matrix itself into clusters of different striatopallidal projection neurons. We directly tested this hypothesis in squirrel monkeys by comparing the distributions of striatal output neurons retrogradely labeled from the two pallidal segments. Striatopallidal neurons labeled by small injections confined to either the external pallidum (GPe) or the internal pallidum (GPi) formed small clusters ("matrisomes") in the matrix compartment of the putamen. However, contrary to previous predictions, labeled matrisomes projecting to GPe were not systematically separated from those projecting to GPi. They could overlap extensively, and within individual matrisomes GPe-projecting neurons and GPi-projecting neurons were extensively intermixed. Double-retrograde labeling analysis in single sections demonstrated that only 2.1 +/- 2.7% of labeled striatal neurons were doubly labeled from both GPe and GPi--a number not significantly different from zero. GPe-projecting and GPi-projecting neurons in the putamen also differed sharply in their expression of enkephalin-like immunoreactivity: 71.3 +/- 7.6% of the neurons labeled by GPe injections were enkephalin positive, in contrast to 10.0 +/- 3.6% of the neurons labeled by GPi injections. These results suggest that in the primate, populations of striatopallidal output neurons are grouped in clusters in the matrix, but that individual neurons in any given cluster project either to GPe or to GPi. Matrisomal clustering may thus coordinate signals sent into the direct and indirect pathways of the basal ganglia from distributed populations of projection neurons in the striatum.

Methionine enkephalin-like immunoreactivity, substance P-like immunoreactivity and β-endorphin-like immunoreactivity post∼mortem stability in rat pituitary

Significant post-mortem changes in peptide concentration occur within the previously unstudied timeframe, i.e. within 1 h, for the proenkephalin A, proopiomelanoccortin, and tachykinin neuropeptidergic systems in the pituitary. These data differ from data obtained in other studies that concluded that peptides are stable for up to 72 h post-mortem. The post-mortem stability of the three neuropeptides, methionine enkephalin, substance P, and β-endorphin, was studied in the rat pituitary to test the hypothesis that significant post-mortem concentration changes of those three neuropeptides occur in the immediate post-mortem time period.

Avian auditory pathways show met-enkephalin-like immunoreactivity

Pathways associated with a recently defined region of the avian auditory thalamus, the shell of the nucleus ovoidalis (Ov), were examined for met-enkephalin immunoreactivity. The presence of enkephalin-like immunoreactive (ELI) perikarya within the medial margin of the inferior colliculus (ICM), afferent to the Ov shell, implicated ICM as a source of ELI fibers within the Ov shell and tract. The shell also contained ELI perikarya and its targets, including the ventromedial hypothalamus and caudoventral paleostriatal complex, were characterized by ELI fields. These data suggest that enkephalinergic auditory pathways, in parallel with traditionally recognized auditory projections, target regions of the avian basal forebrain.

Effects of antibodies against acetylcholinesterase on the expression of peptides and catecholamine synthesizing enzymes in the rat adrenal gland

In the rat, systemic administration of murine monoclonal antibodies against acetylcholinesterase caused rapid piloerection and ptosis (within 30–60 min after the injection). Using indirect immunohistochemistry the effect of these antibodies on peptides and enzyme expression was studied in the rat adrenal gland. Four days after antibody administration a total disappearance of acetylcholinesterase-immunoreactive fibers was observed. However, groups of acetylcholinesterase-immunoreactive chromaffin cells and intramedullary ganglion cells, both cell types showing acetylcholinesterase immunoreactivity also in the control adrenal medulla, expressed increased immunoreactivity. Analysis revealed that the acetylcholinesterase-immunoreactive chromaffin cell groups lackedphenylethanolamine- N-methyltransferase staining both in controls and treated rats. Antibody administration also affected levels of several peptides present in nerve fibers and chromaffin cells. Thus, the number of cells expressing enkephalin, calcitonin gene-related peptide and galanin was dramatically increased compared to the very few cells observed containing these three peptides in the normal gland. The majority of cells expressing enkephalin after antibody treatment also showedphenylethanolamine- N-methyltransferase immunoreactivity. In contrast, the few chromaffin cells expressing strong enkephalin-like immunoreactivity in controls werephenylethanolamine- N-methyltransferase negative. The sparse networks of calcitonin gene-related peptide- and galanin-positive fibers found in control adrenals were unchanged after the antibody treatment. However, the dense network of enkephalin varicose fibers totally disappeared after the antibody injection. A few substance P- and somatostatin-immunoreactive cells, not present in the normal gland, appeared after administration of the antibodies, whereas no changes were encountered with regard to immunoreactive nerve fibers. No clear differences between normal and treated animals could be observed in chromaffin cells with regard to immunoreactivity for neuropeptide Y or any of the four catecholamine-synthesizing enzymes, tyrosine hydroxylase, aromatic l-amino acid decarboxylase, dopamine β-hydroxylase orphenylethanolamine- N-methyltransferase. The present findings demonstrating a disappearance of acetylcholinesterase- and enkephalin-immunoreactive nerve fibers in the adrenal gland after intravenous injection of acetylcholinesterase antibodies support earlier reports showing that these antibodies cause degeneration of preganglionic fibers, and that neuronal decentralization of the adrenal gland induces marked increases in the levels of several peptides in chromaffin cells.

Different subsets of displaced ganglion cells in the pigeon retina exhibit cholecystokinin-like and enkephalin-like immunoreactivities

Immunohistochemical and retrograde tracing techniques were combined in order to identify chemically specific displaced ganglion cells in the pigeon retina. About 15% of the displaced ganglion cells that were retrogradely labeled following injections of different tracers into the accessory optic nucleus were shown to contain cholecystokinin 8-like immunoreactivity. These cells were medium to large (15–30 μm) and located mostly in the peripheral retina. Another population of about 9% of the retrogradely labeled displaced ganglion cells was shown to contain leucine-enkephalin-like immunoreactivity. These cells were medium-sized (11–18 μm) and distributed almost evenly throughout the retina. These two types of displaced ganglion cells represent together only about 0.1% of the total number of ganglion cells in the pigeon retina. Taken together with previous results, these data indicate that the displaced ganglion cells of the avian retina may comprise several chemically specific cell types. The present results also contribute information on the chemical heterogeneity of retinal ganglion cells.

Differential increases of neurokinin B- and enkephalin-like immunoreactivities and their mRNAs after chronic haloperidol treatment in the rat

Changes in neurokinin B-like immunoreactivity (NKB-IR) and neurokinin B mRNA were investigated after daily injection of haloperidol for 10 days on adjacent sections by means of immunocytochemistry and in situ hybridization in the caudate putamen of the rat. In the dorsal striatum the number of NKB immunoreactive perikarya and the staining intensity of striatal efferents increased. The number of NKB mRNA-expressing cells (45%) and the grain density over single positive cells (37%) were significantly higher after the neuroleptic treatment. The levels for enkephalin mRNA were uniformly increased throughout the rostrocaudal extent of the caudate putamen (85%). A main difference to the enkephalin system was that the dorsal pallidum was nearly devoid of NKB-IR in untreated as well as in haloperidol-treated animals. The present data for the first time provide evidence for the regulation of the biosynthesis of NKB after pharmacological intervention.

Comparative distribution of neurokinin B-, substance P- and enkephalin-like immunoreactivities and neurokinin B messenger RNA in the basal forebrain of the rat: Evidence for neurochemical compartmentation

The distribution of neurokinin B was investigated in the basal forebrain of the rat by immunocytochemistry with an antibody directed against neurokinin B and with a second antiserum directed to a peptide sequence contained within its precursor and by means of in situ hybridization. The staining pattern was compared in closely adjacent sections to that of substance P- and enkephalin-like immunoreactivities. Cholecystokinin immunoreactivity was used to delineate the apparent dorsolateral border of the ventral pallidum with the nucleus accumbens. Remarkable similarities are found in the distribution of these peptides in the basal forebrain, especially in its ventral part. The coarse band-like terminal staining pattern (woolly fibers) that has been shown by others for substance P- and enkephalin-like immunoreactivity, is also observed for neurokinin B-like immunoreactivity, mainly in the ventral pallidum. Medium-sized cells are found arranged in clusters or singularly within the caudate-putamen even without colchicine. A band of strong neurokinin B immunoreactivity extends just underneath the dorsal pallidum to the amygdala. In comparison to enkephalin the most distinct observation is that neurokinin B immunoreactivity is not present in the dorsal pallidum (global pallidus). Neurokinin B immumoreactivity was not found in the pars reticulata of the substantia nigra which is strongly immunopositive for substance P. The number of cells detected by in situ hybridization was higher compared to the immunopositive perikarya throughout the basal ganglia. The staining pattern observed reflects a partial overlap with the substance P and enkephalin system although a differential distribution for each of these peptides was observed for cell bodies and axons terminals.