Dynorphin immunocytochemistry in the rat central nervous system

Distribution of opiate receptors within visual structures of the cat brain

The distributions of mu, delta, and kappa opiate receptors within visual regions in the cat cortex, thalamus and midbrain were determined by in vitro autoradiography. The overall distribution of receptors was examined using [3H]-etorphine, a ligand that nonselectively labels all types of opiate receptors. [3H]-[D-Ala2, N-Me-Phe4,Gly(ol)5]-enkephalin (DAGO) was used to selectively label mu receptors, [3H]-[D-Pen2, 5]-enkephalin (DPDPE) for delta receptors, and [3H]-bremazocine for kappa receptors. Each of the areas examined showed clear opiate receptor binding with [3H]-etorphine and a differential distribution of mu, delta, and kappa receptors. Compared to other cortical regions, opiate binding in layers 3 and 4 of areas 17 and 18 was sparse. In the adjacent areas a more uniform distribution across layers was observed. The density of kappa opiate receptors was greater in cortex than in subcortical structures, whereas the reverse was the case for mu receptors. Nevertheless, all three types of opiate receptors were found in the ventral and dorsal subdivisions of the lateral geniculate (LGN), the pulvinar complex, and the suprageniculate nucleus. In the midbrain, the superficial layers of the superior colliculus were heavily labelled with the mu receptor ligand, and modestly with the kappa ligand. Compared with other midbrain and diencephalic areas, delta binding was low in the superior colliculus. These results suggest that the diverse effects of opiates on visual perception are mediated by the unique distributions of opiate receptor types throughout the visual areas in the brain.

Multiple brain sites sensitive to feeding stimulation by opioid agonists: a cannula-mapping study

Evidence suggests that brain opioid receptors of the mu, delta and kappa subtypes may be involved in the control of feeding behavior. However, limited information is available regarding the specific anatomical location of these feeding relevant opioid receptors. To address this problem, we microinjected three opioid agonists, morphine, (D-Ala2)-Met-enkephalinamide (DALA) or MR 2034, into one of 15 different brain areas and measured the subsequent feeding responses of satiated rats. Morphine (25 nmol) and DALA (6.8 nmol) both elicited strong feeding responses from the same five brain areas, namely, the paraventricular, dorsomedial and lateral hypothalamus, as well as from sites within the septum and amygdala. No other brain sites yielded significant responses to these opioid receptor agonists. In contrast to this anatomically specific pattern of effects, the opioid agonist MR 2034 (8.6 nmol) produced a feeding response which was generally smaller in magnitude and had little anatomical specificity. These findings suggest that opioid receptor systems for stimulating feeding exist in multiple discrete brain areas. Of the regions tested, specific sites within the hypothalamus, septum and amygdala are distinguished as being most sensitive to feeding stimulation by morphine and DALA.

Different susceptibilities of long-term potentiations in CA3 and CA1 regions of guinea pig hippocampal slices to nootropic drugs

Effects of the nootropic drugs, piracetam and bifemelane, on long-term potentiation (LTP) of population spikes in the CA3 and CA1 regions of guinea pig hippocampal slices were investigated. Piracetam (10(-6) to 10(-4) M) and bifemelane (10(-8) to 10(-6) M) significantly augmented the LTP in the CA3 region. The effects of these drugs were inhibited by scopolamine (10(-6) M). However, the LTP in the CA1 region was not affected by piracetam and bifemelane even at highly effective concentrations (10(-5) and 10(-6) M, respectively). Thus, the LTP in the CA3 is more susceptible to nootropic drugs than in the CA1.

Role of the ventromedial hypothalamus in the regulation of adenohypophyseal immunoreactive dynorphin in the rat

In this study, we have examined the role of the dorsomedial (DMH), ventromedial (VMH) and arcuate (ARH) nuclei of the hypothalamus in the control of hypothalamic and pituitary immunoreactive (ir) dynorphin (Dyn) A and ir-Dyn B in the rat, by evaluating the effect of discrete, bilateral radiofrequency lesions in these structures. Lesions limited to the VMH reduced the content of ir-Dyn in the anterior pituitary but not in the neurointermediate lobe or in the hypothalamus. Gel chromatographic analysis of anterior pituitary extracts confirmed that ir-Dyn is mainly associated with high molecular weight forms containing Dyn A and Dyn B in their sequence. Anterior pituitary extracts of VMH-lesioned rats displayed a clearly lower proportion of these forms. Destruction of the DMH affected only the hypothalamic content of ir-Dyn; ablation of the ARH did not cause any significant change. Our results suggest that ablation of the VMH may disrupt critical neuronal connections to the median eminence originating in this nucleus or crossing it and participating in control of the adenohypophyseal pool of ir-Dyn.

Distribution of opioid peptides in the preoptic region: immunohistochemical evidence for a steroid-sensitive enkephalin sexual dimorphism

The distribution of cells and fibers that contain opioid peptides within the preoptic region of the rat was examined immunohistochemically. Cells and/or fibers that contain peptides derived from each of the three major opioid peptide families were differentially stained by using antisera that recognize unique derivatives of each precursor molecule and do not cross-react with members of the other opioid peptide families. A beta-endorphin (beta E) antiserum was used to stain fibers that contain peptides derived from the proopiomelanocortin molecule, and dynorphin-containing cells were identified by using an antiserum directed toward dynorphin B (Dyn B) that does not show detectable cross-reactivity with enkephalin-related peptides. An antiserum raised against peptide E (PE), which does not appear to cross-react significantly with dynorphin peptides, was used to localize enkephalin cells and fibers. Each family of opioid peptides showed a unique distribution in the preoptic region. beta E-immunoreactive fibers were primarily localized to the preoptic part of the periventricular nucleus, with moderate densities of fibers contained in the anteroventral periventricular nucleus (AVPv) and medial preoptic nucleus (MPN). Dyn B-immunoreactive fibers showed a somewhat more uniform distribution throughout the region, and only a few Dyn B-stained cells bodies were found within the medial preoptic area. In contrast, the preoptic region contained hundreds of PE-immunoreactive cells, which were particularly numerous within the AVPv, MPN, and anterodorsal preoptic nucleus. The AVPv and MPN also contained discretely localized plexuses of PE-stained fibers. Although the overall distributions of opioid peptide-containing fibers within the preoptic region were quite similar in male and female rats, differential distributions of fibers were found in certain nuclei such as the AVPv and MPN, and they were correlated with previously identified cytoarchitectonic sexual dimorphisms. Such differential distributions were particularly distinct for enkephalin-containing fibers. Although the AVPv is larger in female rats, it contained more PE-immunoreactive cell bodies in male rats, and we have shown here that this sexual dimorphism appears to be at least partially dependent on perinatal levels of gonadal steroids. In contrast, no difference in the number of PE-stained cells was found within the anterodorsal preoptic nucleus of male and female animals, indicating that sexual differences are not a general characteristic of enkephalinergic cells in the preoptic region of the rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Lateral hypothalamic dynorphinergic efferents to the amygdala and brainstem in the rat

Dynorphin is present within perikarya of the lateral hypothalamus (LH) and perifornical nucleus (PeF), and within nerve terminals of the central nucleus of the amygdala, central grey, parabrachial nucleus, and the dorsal vagal complex (nucleus of the solitary tract and dorsal motor nucleus of the vagus). Each of these nuclei receive efferent projections from the LH and PeF. In this study, the possibility that dynorphin cells with LH and PeF innervate each of these nuclei was investigated using a combined retrograde tracing-immunofluorescence technique. As enkephalinergic perikarya have also been localized to LH and PeF, peptide E (an enkephalin precursor fragment) was also studied for comparison. Following injections of fast blue into the central nucleus, parabrachial nucleus, central grey, and dorsal vagal complex, numerous retrogradely-labeled dynorphin-immunoreactive neurons were present within the LH and PeF. In comparison, retrogradely-labeled peptide E-immunoreactive cells were infrequently observed. These results suggest the LH and PeF to be a major source of dynorphin to the forebrain and brainstem.

Prodynorphin gene expression in spinal cord is enhanced after traumatic injury in the rat

Levels of mRNAs coding for prodynorphin (Pro-Dyn) and proenkephalin (Pro-Enk) as well as the levels of immunoreactive (ir)-dynorphin (Dyn) and (ir)-Met-enkephalin (Met-Enk) were measured in the spinal cord of rats, 65 h following transection or injury of the spinal cord at the T6 spinal segment. Levels of both Pro-Dyn mRNA and of ir-Dyn were significantly increased between 60 and 150%, above control levels in the whole spinal cord, whereas those of Pro-Enk mRNA and of ir-Met-Enk remained unchanged. The increase in spinal levels of Pro-Dyn mRNA were highest in the areas close to the side of transection and indicate an involvement of the Pro-Dyn opioid system in the response to spinal injury and transection.

Neurochemical organization of the hypothalamic projection to the spinal cord in the rat

The hypothalamus provides a major projection to the spinal cord that innervates primarily lamina I of the dorsal horn and the sympathetic and parasympathetic preganglionic cell columns. We have examined the chemical organization of the neurons that contribute to this pathway by using combined retrograde transport of fluorescent dyes and immunohistochemistry for 15 different putative neurotransmitters or their synthetic enzymes. Our results demonstrate that 5 cytoarchitectonically distinct cell groups in the hypothalamus contribute to the spinal projection and that each has its own predominant chemical types. In the paraventricular nucleus, substantial numbers of hypothalamo-spinal neurons stain with antisera against arginine vasopressin (25-35%), oxytocin (20-25%), and met-enkephalin (10%). About 25% of the neurons with spinal projections in the retrochiasmatic area stain with an antiserum against alpha-melanocyte-stimulating hormone. Nearly 100% of the hypothalamo-spinal neurons in the tuberal lateral hypothalamic area stain with this same antiserum, but these cells do not stain for other proopiomelanocortin-derived peptides, and so probably contain a cross-reacting peptide. This population must be distinguished from an adjacent cell group, in the perifornical region, where many spinal projection neurons stain with antisera against dynorphin (25%) or atrial natriuretic peptide (20%). Finally, in the dorsal hypothalamic area as many as 55-75% of the neurons with spinal projections are dopaminergic, on the basis of their staining with an antiserum against tyrosine hydroxylase. These 5 neurochemically distinct projections from the hypothalamus to the spinal cord are discussed in the context of their possible functional significance.

Peptide injections into the amygdala of conscious rats: effects on blood pressure, heart rate and plasma catecholamines

The central nucleus of the amygdala (Ce) mediates cardiovascular and autonomic changes associated with defense or fear responses. At least 16 different neuropeptides have been identified within nerve terminals within the Ce. The role that these peptides play in the Ce regulation of cardiovascular and autonomic function has been assessed. Neuropeptides were microinjected into the region of the Ce and mean arterial pressure (MAP), heart rate (HR) and plasma catecholamine concentrations were measured. Five of the 16 peptides caused changes of MAP and HR. Thyrotropin releasing factor (TRF) and calcitonin gene-related peptide (CGRP) induced increases of MAP and HR. Angiotensin-II (A-II) and somatostatin-28 (SS-28) injection produced increases of MAP and decreases of HR. Bombesin (Bom) injections into the Ce induced an increase of MAP but did not alter HR. Corticotropin releasing factor (CRF), TRF and CGRP were the only peptides found to increase plasma catecholamine concentrations. These results support the conclusion that the Ce contains several peptides that could be involved in the regulation of cardiovascular and autonomic nervous system function. A role of the amygdala in mediating the observed effects of CRF, TRF, CGRP, A-II, SS-28, and Bom is suggested by these studies.

Lithium increases dynorphin A(1-8) and prodynorphin mRNA levels in the basal ganglia of rats

The aim of this study was to understand the possible influence of the antimanic drug, lithium, and the neuroleptic, haloperidol, alone or in combination, on the regulation of dynorphin biosynthesis in the striatum. The study was done using male Fisher-344 rats subjected to a regimen of subchronic administration of lithium chloride (4 mEq/kg/day for 1,2,4 or 6 days, i.p.) or a regimen of chronic oral administration of a diet containing lithium carbonate (1.5 g/kg of the diet). Subchronic administration of lithium increased striatal dynorphin A(1-8)-like immunoreactivity (DN-LI) in a time-related fashion. Immunocytochemistry revealed an increase in DN-LI in fibers and cells clustered in 'patches' throughout striatum. The increase in DN-LI was reversible on cessation of lithium administration. Concurrent administration of lithium and an opiate antagonist, naltrexone, or a dopamine receptor antagonist, haloperidol, did not influence the changes induced by lithium. Chronic oral administration of lithium for 21 days led to an increase in DN-LI in the striatum. Co-administration of haloperidol with the 21 day regimen of lithium administration failed to affect the increase in DN-LI. The prodynorphin mRNA abundance in the striatum was quantitated by a molecular hybridization procedure using a prodynorphin 32P-cRNA probe generated from the Riboprobe system. Evidence from the Northern blot analysis reveals that lithium increases the prodynorphin mRNA abundance in the striatum. These results indicate that lithium affects the dynamics of prodynorphin biosynthesis in the striatum, presumably increasing transcription and/or translational processes.

Dopamine-independent motor behavior following microinjection of rimorphin in the substantia nigra

The motor-activating effects of rimorphin, an opioid peptide derived from prodynorphin, were examined in the substantia nigra pars reticulata of rats. Unilateral microinjections of rimorphin produced dose-dependent contralateral rotational behavior that was antagonized by naloxone, suggesting that these effects were mediated by opiate receptors. Lesions of midbrain dopamine cells with 6-hydroxydopamine (6-OHDA) produced a 95% or greater depletion of tyrosine hydroxylase in the striatum ipsilateral to the lesion, but failed to reduce the number of circles made by the rats. In addition to an overall preservation of rimorphin-induced circling in animals with 6-OHDA lesions, 50% of these rats exhibited circling that was at least 2 standard deviations above the mean of animals without lesions. The motor activating effects of rimorphin, thus, appear to occur independently of the nigrostriatal dopamine system; these effects may instead be mediated by GABAergic efferents in the pars reticulata.

Dopamine-containing neurons in the mammalian central nervous system: electrophysiology and pharmacology

A decade of research culminated in the late 1950's with the demonstration that dopamine was a chemical neurotransmitter within the mammalian brain. Since this time, dopaminergic neuronal systems have been extensively studied using numerous techniques. This paper will review the last 14 years of electrophysiological investigation on neurochemically identified dopamine-containing neurons in the central nervous system. This will include an examination of both the electrophysiological and pharmacological characteristics in these cells, as well as the resulting insights into the regulation of dopamine cell electrical activity which is derived from this work.

Enkephalins interact with substance P-induced aversive behaviour in mice

The effect of the endogenous opioid peptides, methionine-enkephalin (Met-ENK), beta-endorphin (beta-END) and dynorphin-(1-17) (DYN) on the aversive behavior produced by intrathecal (i.t.) administration of substance P (SP) was studied in mice. A low dose of i.t. administered Met-ENK gave a marked reduction of the SP-induced response. In the tail-flick assay, such doses of Met-ENK were ineffective in producing antinociception. At much higher doses, however, Met-ENK obtained antinociceptive activity. In contrast, beta-END and DYN had about the same potency in inhibiting the SP-induced behavioural response and in the tail-flick test, respectively. These results suggest that opioid peptides, particularly enkephalin neurons in the spinal cord influence SP-induced aversive behaviour.

Cytochrome oxidase histochemistry reveals regional subdivisions in the rat periaqueductal gray matter

The identification of different anatomical regions of the periaqueductal gray matter of rats was addressed in the present study by using the histochemical staining for the mitochondrial enzyme cytochrome oxidase. At caudal and middle levels, cytochrome oxidase histochemistry clearly demonstrates the existence of four subdivisions: dorsal, dorsolateral, ventrolateral and medial, whereas in sections from the rostral periaqueductal gray matter only two concentric bands are identifiable on the basis of the degree of cytochrome oxidase activity.

Increased staining of immunoreactive dynorphin cell bodies in the deafferented spinal cord of the rat

This study examined the distribution of immunoreactive dynorphin neurons in the lumbar dorsal horn of unilaterally deafferented, colchicine-treated rats. Ipsilateral to a multiple dorsal rhizotomy there was a significant increase both in the number and intensity of staining of dynorphin-immunoreactive cells in laminae I, outer II and V. A comparable change was seen in animals that were deafferented by sciatic nerve section. Enkephalin immunoreactivity was not altered under these conditions. These results indicate that many forms of injury, not all of which result in increased nociceptive input, can increase the level of dynorphin in spinal cord neurons.

Dynorphin1-17 reduces the inhibitory actions of mu- and delta-selective opioid agonists in cortical neurons of the rat in vivo

Spontaneous and L-glutamate-evoked neuronal activity was recorded extracellularly from neocortical neurons of rats. Opioid agonists with preference for different receptor types were applied microiontophoretically or pneumatically from multibarrelled micropipettes. Morphine (mu-selective), [D-Ala2,D-Leu5]enkephalin (delta-selective; DADL) and the kappa-selective agonist dynorphin1-17 (DYN 17) suppressed spontaneous and evoked neuronal activity in a naloxone-reversible manner. In a substantial number of neurons the inhibitory effect of DADL and morphine was reduced or abolished by DYN 17. This antagonistic action was often observed with DYN 17 levels that did not influence the discharge activity by itself. The physiological significance of this observation remains to be elucidated.

The significance of multiple CNS opioid receptor types: a review of critical considerations relating to technical details and anatomy in the study of central opioid actions

The study of the CNS actions of opioids is complicated by the presence of both multiple opioid receptors and endogenous ligands in the brain. The recent descriptions of opioid isoreceptors, of tonic opioid systems, and of multiple opioid receptors on a single neuron are further technical details which must be considered. In the use of various opiates and opioid peptides to study physiological systems, the multiple opioid affinities of these compounds, as well as potential non-opioid actions, must be controlled for in the experimental design. In conjunction with the multiple receptor affinities of various opiates is the problem of receptor dualism with some drugs; particularly with the agonist/antagonist analgesics. Species differences in the relative proportions of different opioid receptor populations also limit any generalizations of a finding in one species. These limitations in the study of opioid receptors will be discussed with reference to previous neurochemical, neuroendocrine, electrophysiological and behavioral reports of multiple opioid receptors.

Immunocytochemical identification of long ascending peptidergic neurons contributing to the spinoreticular tract in the rat

In the present study, we examined the peptidergic content of lumbar spinoreticular tract neurons in the colchicine-treated rat. This was accomplished by combining the retrograde transport of the fluorescent dye True Blue with the immunocytochemical labeling of neurons containing cholecystokinin-8, dynorphin A1-8, somatostatin, substance P or vasoactive intestinal polypeptide. After True Blue injections into the caudal bulbar reticular formation, separate populations of retrogradely labeled cells were identified as containing cholecystokinin-like, dynorphin-like, substance P-like or vasoactive intestinal polypeptide-like immunoreactivity. Retrogradely labeled somatostatin-like neurons were not identified in any of the animals examined. Each population of double-labeled cells showed a different distribution in the lumbar spinal cord. The highest yield of double-labeling occurred for cholecystokinin, with 16% of all intrinsic cholecystokinin-like neurons containing True Blue. These double labeled neurons were found predominantly at the border between lamina VII and the central canal region. About 11% of intrinsic vasoactive intestinal polypeptide-like neurons in the lumbar spinal cord were retrogradely labeled from the bulbar reticular formation. These neurons were found mostly in the lateral spinal nucleus, with only a few double-labeled cells located deep in the gray matter. Dynorphin-like double-labeled neurons were localized predominantly near the central canal; a smaller population was also seen in the lateral spinal nucleus. It was found that double-labeled dynorphin-like neurons made up 8% of all intrinsic dynorphin-like neurons. Retrogradely-labeled substance P-like neurons were rare; the few double-labeled neurons were found in the lateral spinal nucleus and lateral lamina V. These findings suggest a significant role for spinal cord peptides in long ascending systems beyond their involvement in local circuit physiology.

The survival of dentate gyrus neurons in dissociated culture

Using a technique for dissociating cells from the area dentata of postnatal rats, we have been able to routinely establish low density cultures of dentate granule neurons that can be grown in the presence or absence of serum. Non-granule neurons from the hilar region and glial cells (both astrocytes and oligodendrocytes) are also present, but can be readily distinguished from the granule cells in these cultures. Unlike dissociated hippocampal pyramidal cells, which frequently resemble their in vivo morphology, dissociated dentate granule cells bear little resemblance to their normal in vivo counterparts, but are very similar in appearance to the ectopic granule cells seen in the reeler mouse. This suggests that extrinsic factors are the principal determinants of the mature form which granule neurons assume in vivo. On the other hand, the dissociated granule cells are able to express certain other aspects of their in vivo phenotype including the synthesis and transport of an antigen which is characteristically found in mossy fibers. Certain neuropeptide-containing non-granule neurons found in these cultures are also capable of maintaining aspects of their in vivo phenotype.

Striatal neurochemistry of dynorphin-(1-13): in vivo electrochemical semidifferential analyses

The striatal neurochemistry of dynorphin-(1-13) was studied by simultaneously measuring extracellular dopamine and serotonin voltammetrically and in vivo after the injection of dynorphin-(1-13) to male Sprague-Dawley rats. The subcutaneous administration of dynorphin-(1-13), at a dose (1.5 mg/kg), known to exert CNS mediated behavioral effects, caused a statistically significant decrease in extracellular dopamine and a statistically significant increase in extracellular serotonin from rat anterior striatum. These parallel and opposite effects of dynorphin-(1-13) on these biogenic amines occurred gradually during a three hour time course. Maximal effects on dopamine (55%) and on serotonin (62%) occurred at the end of the three hour period of study. Mean effects on dopamine and serotonin (35% and 42% respectively) were averaged from scan results over the three hour period of study; the results were significantly different from control values. Dose response studies showed that a lower dose of dynorphin-(1-13) (0.5 mg/kg sc) had little or no effect on the alteration of these biogenic amines from striatum. The highest dose of dynorphin-(1-13) studied, (3.0 mg/kg sc), predictably and significantly altered extracellular biogenic amines. The dose response, however, was not incremental. The results are consistent with the role of dynorphin-(1-13) as a neuromodulatory peptide. The results further support the concept that the neuromodulatory role of dynorphin-(1-13) may take place through neurotransmitter regulation. The data suggest that the function of dynorphin-(1-13) may be a presynaptic modulation of neurotransmission in striatum.

The distribution of substance P-, enkephalin- and dynorphin-immunoreactive neurons in the medulla of the rat and their contribution to bulbospinal pathways

This study examined the medullary distribution of peptide-containing neurons at the origin of bulbospinal pathways in the rat. Antisera directed against substance P, methionine-enkephalin-arg-gly-leu and dynorphin B were used on sections in which spinally projecting brainstem neurons had been identified by the retrograde transport of a protein-gold complex that was injected into the spinal cord. Both the relative numbers and distribution of the different peptide-immunoreactive spinally projecting neurons differed. Methionine-enkephalin-immunoreactive neurons were twice as numerous as the substance P-immunoreactive cells and seven times more numerous than the dynorphin B-positive neurons. The methionine-enkephalin cells were found in all medullary raphé nuclei, and in the ventromedial and ventrolateral medullary reticular formation. Caudally, the methionine-enkephalin cells were concentrated laterally; more rostrally they were located more medially. Three major loci of methionine-enkephalin-immunoreactive cells were found: (1) the nucleus reticularis paragigantocellularis lateralis, at levels caudal to the facial nucleus, (2) the B3 cell group (nucleus raphé magnus and the nucleus reticularis magnocellularis, pars alpha) and the most rostral part of the B1 and B2 cell groups (nuclei raphé pallidus and obscurus), (3) a dense cluster of cells that flanks the dorsal surface of the dorsal accessory olive (referred to as the nucleus interfascicularis hypoglossi, pars dorsalis). Substance P-like cells were seen in all raphé nuclei except for the most anterior portion of the B3 cell group. Substance P-immunoreactive cells were also seen in both the ventromedial (nuclei reticularis ventralis and magnocellularis) and ventrolateral medulla (nucleus reticularis paragigantocellularis lateralis). Finally there was a dense concentration of substance P neurons in the nucleus interfascicularis hypoglossi, pars ventralis. The distribution of dynorphin-immunoreactive neurons differed significantly from that of methionine-enkephalin and substance P. Dynorphin cells were almost exclusively found in the ventrolateral medulla (nucleus reticularis paragigantocellularis lateralis), at all levels between the lateral reticular nucleus and the caudal pole of the facial nucleus. The proportion of each of these peptidergic-immunoreactive cells at the origin of bulbospinal pathways differed considerably. Substance P spinally projecting neurons were more numerous than methionine-enkephalin spinally projecting neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of dynorphin (1-8) on movement: non-opiate effects and structure-activity relationship

Cell bodies in the head of the caudate nucleus that synthesize prodynorphin peptides form a substantial projection to the substantia nigra pars reticulata (SNR). The discovery of this pathway suggested an involvement of prodynorphin products in motor control. The effects of unilateral nigral microinjections of prodynorphin products were tested in an in vivo circling model. Dynorphin (1-8), dynorphin (1-7), dynorphin (1-6), dynorphin (2-17) (des-Tyr-dynorphin), and Leu-enkephalin induced spontaneous contralateral circling at 20 nmol doses. The effect of dynorphin (1-8) was dose dependent and was not blocked by pretreatment with naloxone or WIN 44,441-3. These findings clearly demonstrate the dynorphinergic involvement in nigral motor control which may consist of an opioid and a non-opioid component.

Separable roles of hippocampal granule cells in forgetting and pyramidal cells in remembering spatial information

To investigate the roles individual hippocampal cell groups play in processing of spatial information for memory, we administered low-intensity electrical stimulation to the granule cells, CA3 and CA1 pyramidal cells of the dorsal hippocampus at selected times before and after acquisition of the solution to a radial maze win-stay task. Stimulation of any of the 3 cells populations yielded a variable duration anterograde disruption of memory performance, while stimulation of dentate gyrus granule cells alone produced a declarative memory-specific retrograde amnesia. The amnestic effect of granule cell stimulation was not associated with after discharges in the hippocampus and was prevented by systemic administration of the opiate antagonist naloxone. Our results support the view that this electrical stimulus does not disrupt, but rather, activates the normal function of the granule cell system, resulting in erasure of information held in declarative memory. In contrast, similar activation of the pyramidal cell system does not yield retrograde amnesia, suggesting a normal role for these cells in promoting memory for spatial information.

Localization of preproenkephalin mRNA in the rat brain and spinal cord by in situ hybridization

To determine the localization in rat brain and spinal cord of individual neurons that contain the messenger RNA coding for the opioid peptide precursor preproenkephalin, we performed in situ hybridization with a tritiated cDNA probe complementary to a protion of preproenkephalin mRNA. We observed autoradiographic signal over the cytoplasm of neurons of many regions of the central nervous system. Several types of controls indicated specificity of the labeling. Neurons containing preproenkephalin mRNA were found in the piriform cortex, ventral tenia tecta, several regions of the neocortex, nucleus accumbens, olfactory tubercle, caudate-putamen, lateral septum, bed nucleus of the stria terminalis, diagonal band of Broca, preoptic area, amygdala (especially central nucleus, with fewer labeled neurons in all other nuclei), hippocampal formation, anterior hypothalamic nucleus, perifornical region, lateral hypothalamus, paraventricular nucleus, dorsomedial and ventromedial hypothalamic nuclei, arcuate nucleus, dorsal and ventral premamillary nuclei, medial mamillary nucleus, lateral geniculate nucleus, zona incerta, periaqueductal gray, midbrain reticular formation, ventral tegmental area of Tsai, inferior colliculus, dorsal and ventral tegmental nuclei of Gudden, dorsal and ventral parabrachial nuclei, pontine and medullary reticular formation, several portions of the raphe nuclei, nucleus of the solitary tract, nucleus of the spinal trigeminal tract (especially substantia gelatinosa), ventral and dorsal cochlear nuclei, medial and spinal vestibular nuclei, cuneate and external cuneate nuclei, gracile nucleus, superior olive, nucleus of the trapezoid body, some deep cerebellar nuclei, Golgi neurons in the cerebellum, and most laminae of the spinal cord. In most of these brain regions, the present results indicate that many more neurons contain preproenkephalin mRNA than have been appreciated previously on the basis of immunocytochemistry.

Supraspinal morphine and descending inhibitions acting on the dorsal horn of the rat

1. Recordings were made from thirty-nine convergent neurones in the lumbar enlargement of the rat spinal cord. These neurones were activated by both innocuous and noxious stimuli applied to their excitatory receptive fields located on the extremity of the ipsilateral hind paw. Transcutaneous application of suprathreshold 2 ms square-wave pulses to the centre of the receptive field resulted in responses to A- and C-fibre activation being observed; a mean of 18.8 +/- 1.8 C-fibre latency spikes was evoked per stimulus. This type of response was inhibited by applying noxious conditioning stimuli to heterotopic body areas; immersing the tail in a 52 degrees C water-bath caused a mean 54.5 +/- 2.3% inhibition of the C-fibre-evoked response; such inhibitory processes have been termed diffuse noxious inhibitory controls (d.n.i.c.). 2. The effects of microinjections of morphine (5 micrograms; 0.2 microliter) on both the unconditioned C-fibre-evoked response and inhibitory processes triggered from the tail were investigated in an attempt to answer two questions: (a) does morphine increase tonic descending inhibitory processes and (b) what are the effects of morphine on descending inhibitory processes triggered by noxious stimuli? 3. The predominant effect of periaqueductal grey matter (p.a.g.) morphine on the C-fibre-evoked responses was a facilitation: 51% of cells had their C-fibre-evoked responses increased by morphine (by roughly 50%); 31% of cells were not influenced while the remaining 18% of units were depressed; however the cells classified as depressed were only marginally so. No clear relationships were found either between the microinjection sites in the p.a.g. and their corresponding effects or between the number of C-fibre-spikes evoked in the control sequences and the subsequent effect of morphine. 4. While d.n.i.c. was not altered by morphine in 56% of cases, it was clearly reduced in the remaining cells. The effects were immediate but peaked at 40 min following the microinjection (a mean 77% reduction) and then returned towards control values. All but three of the corresponding microinjection sites were such as to include the medio-ventral p.a.g. including the nucleus raphé dorsalis. In contrast none of the cases where d.n.i.c. was unaltered included microinjection sites in this region. 5. No relationship was found between the changes in d.n.i.c. and the number of spikes evoked in the control sequences, or the changes in the C-fibre responses. 6. Autoradiographic controls using [3H]morphine showed a large diffusion of the drug within an area of about 0.75 mm around the tip of the cannula.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of met-enkephalin-, dynorphin A-, and neurotensin-immunoreactive neurons in the cat and rat spinal cords: I. Lumbar cord

This study compared the distribution of methionine enkephalin-, dynorphin A 1-8-, and neurotensin-immunoreactive (IR) perikarya in laminae I and IV-VII of selected segments of lumbar spinal cord of cat(L5) and rat(4). Immunoreactive neurons for each peptide were found throughout the dorsal horn and dorsal lamina VII but were quantified only within laminae I and IV-VII. In lamina I, both large (greater than 20 micron) and small (less than 20 micron) IR neurons were identified. Large IR neurons for each peptide in both species resembled Waldeyer neurons studied by Golgi stain and were outnumbered by small IR neurons. Comparison among the laminae of the distribution of met-enkephalin IR neurons showed a similar pattern in the two species with the majority of IR neurons (greater than 65%) in laminae V and VI. Differences in laminar distribution occurred between species for the other peptides. Dynorphin IR neurons were greatest in number in lamina V in rat but greatest in number in laminae I and V in cat. Neurotensin IR neurons occurred predominantly in cat lamina I but were nearly equal in density in rat laminae I and VI. The topographic distribution of each peptide in laminae V and VI was similar between the two species with IR neurons occurring laterally in lamina V and more medially in lamina VI. Comparisons between species of the numbers of IR neurons/segment indicated distinct relationships for each peptide. The number of met-enkephalin IR neurons in laminae of cat L5 was generally two times greater than the number of IR neurons in the same laminae of rat L4, except in laminae I and IV, where the numbers were nearly equal. In contrast, the number of dynorphin IR neurons in cat laminae was generally one-half the number in rat, except in lamina I, where the number in cat was two times greater than rat. A high degree of variability occurred in laminar comparisons of neurotensin IR neurons. Neurotensin IR neurons in lamina I of cat outnumbered those of rat 2:1, but in laminae IV-VII, the ratio of cat to rat IR neurons varied from 1:1 to 1:20. The met-enkephalin, dynorphin, and neurotensin IR neurons quantified in this study may be interneurons or may serve as projection neurons to brainstem and/or thalamic nuclei. The observed differences in distribution may be relevant to differences in spinal cord physiology in the two species.

Dynorphin(1-8) immunoreactivity in brainstem and hypothalamic nuclei of normotensive and age-matched hypertensive rat strains

The concentration of dynorphin (1-8) immunoreactivity [ir-dyn(1-8)] was measured in 10 hypothalamic and 11 brainstem nuclei of Sprague-Dawley (SD) and 6- and 14-week old Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats. The highest concentrations of ir-dyn(1-8) were found in the lateral preoptic and lateral hypothalamic areas of the hypothalamus and the solitary tract nucleus of the brainstem. Levels of the peptide were low in other brainstem nuclei compared to hypothalamic areas. There was a significant reduction in ir-dyn(1-8) concentrations at 14 weeks of age compared to 6 weeks of age in all 9 nuclei examined in SH and WKY rats. However, there were no differences between the strains at either age. These changes may be related to the increase in blood pressure that occurs in both SH and WKY rats over this age range although other factors must also be involved to produce the higher blood pressure levels of the SH rat.

Opposite effects of ventral tegmental and periaqueductal gray morphine injections on lateral hypothalamic stimulation-induced feeding

Eating was induced in sated animals by lateral hypothalamic electrical stimulation following central microinjections of morphine or saline. With stimulation intensity fixed at a moderate level, time to eat 3 food pellets of 45 mg decreased with increases in stimulation frequency, approaching an asymptote near 7 s at approximately 70 Hz. Ventral tegmental area morphine injections (0.8-8 nmol) reduced the minimum frequency required to produce eating of 3 pellets within 20 s and reduced the frequency at which asymptotic performance was produced; it did not substantially change the speed of eating at which performance approached asymptote. Periaqueductal gray morphine injections (1.6-16 nmol) had the opposite effect; they increased the stimulation frequency required to meet either the 20 s (maximum) or the 7 s (asymptotic) response criterion. Since the ventral tegmental injections did not alter the absolute level of asymptotic performance, the changes in eating threshold associated with these injections are assumed to reflect motivational influences of morphine.

Autoradiographic localization in rat brain of kappa opiate binding sites labelled by [3H]bremazocine

[3H]Bremazocine, in the presence of saturating concentrations of mu and delta receptor blocking agents, was used to label putative kappa opiate binding sites in rat brain. The binding of [3H]bremazocine under these conditions was completely displaced with high affinity by U-50488H and dynorphin1-17, and the potency of a series of opiate ligands was consistent with an action at kappa receptors. Therefore, [3H]bremazocine, in the presence of mu and delta blockers, was used to localize U-50488H-displaceable kappa binding sites by autoradiography. A distribution different from that of mu and delta receptors was seen, with levels highest in the claustrum, striatum, medial preoptic area, suprachiasmatic nucleus, medial amygdala and superior layer of the superior colliculus. The results show that the U-50488H-displaceable kappa sites have a distinct distribution which is discussed in terms of the possible functional roles of kappa receptors.

Distribution of opioid binding sites in the guinea pig hippocampus as compared to the rat: a quantitative analysis

In vitro autoradiography of cryostat sections revealed major differences between the distribution of opioid binding sites in the hippocampus of the guinea pig and the rat. Only very low binding was found in the pyramidal cell layer, the dentate granular cell layer and the commissural-associational zone of the dentate molecular layer of the guinea pig, whereas these areas were moderately to densely labeled in the rat. In the guinea pig an enrichment of sites was observed in the terminal field of the mossy fiber system in the hilus which was absent in the rat. Binding sites in the guinea pig were found to be mainly of the kappa and mu type. The distribution of [Leu]enkephalin immunoreactivity does not correlate well with the distribution of delta opioid binding sites in the hippocampus. Quantification of opioid binding sites in the hippocampus demonstrates that no one type of site can be assigned to a specific hippocampal subregion nor does the intensity or the pattern of distribution of binding types agree well with the distribution of endogenous opioid peptides.

Striato-nigral dynorphin and substance P pathways in the rat. I. Biochemical and immunohistochemical studies

The effect of striatal ibotenic acid lesions on dynorphin-, substance P- and enkephalin-like immunoreactivities in the substantia nigra has been studied with immunohistochemistry as well as biochemistry. A comparison was made with the effects produced by intranigral ibotenic acid lesion and by 6-hydroxy-dopamine injection into the medial forebrain bundle. In addition, the effect of the striatal lesions on nigral glutamic acid decarboxylase (GAD)-positive structures was analysed with immunohistochemistry. The effect of the lesions was analysed functionally in the Ungerstedt rotational model, in order to obtain a preliminary evaluation of the extent of the lesions. The striatal lesions produced a parallel depletion of dynorphin and substance P levels in the substantia nigra, pars reticulata, ipsilateral to the treated side, which was dependent upon the extent and location of the lesion. Ibotenic acid lesions into the tail and the corpus of the striatum produced stronger nigral-peptide depletion than lesions in the head and the corpus of the striatum. Comparison of placement of lesions and localization of depleted area in the substantia nigra revealed a topographical relationship. Furthermore, the nigral depletion patterns of dynorphin and substance P were similar. The immunohistochemical analysis revealed that also GAD-positive fibers in the pars reticulata to a large extent disappeared after striatal lesions, in parallel to the dynorphin- and substance P-positive fibers. However, the depletion was less pronounced for GAD than for the peptides, probably related to presence of local GABA neurons in the zona reticulata of the substantia nigra. These results indicate that with the types of lesion used in this study it is not possible to provide evidence for a differential localization within the striatum of dynorphin-, substance P- and GABA-positive cell bodies projecting to the substantia nigra. The radioimmunoassay showed that (Leu)- but not (Met)-enkephalin was affected to the same extent as the dynorphin peptides, supporting the view that (Leu)-enkephalin in the pars reticulata of the substantia nigra is derived from proenkephalin B and not from proenkephalin A. In the immunohistochemical analysis (Met)-enkephalin-like immunoreactivity could only be detected in the pars compacta of the substantia nigra and did not seem to be affected by any of the lesions. The striatal lesions produced a behavioural asymmetry, which could be disclosed by stimulating the rats with apomorphine, which produced ipsilateral rotation.(ABSTRACT TRUNCATED AT 400 WORDS)

Coexistence of enkephalin and dynorphin immunoreactivities in neurons in the dorsal gray commissure of the sixth lumbar and first sacral spinal cord segments in rat

The dorsal gray commissure (DGC) of the sixth lumbar (L6) and first sacral (S1) spinal cord segments in the rat has been shown to contain several different peptides, including enkephalin (ENK) and dynorphin (DYN). The present study was conducted to determine if DYN and ENK immunoreactivities coexist in neurons in the DGC in L6 and S1. Coexistence was determined using the elution/restaining technique of Tramu in which sections were stained first with anti-DYN then with anti-ENK after elution of the DYN antiserum. The number and location of DYN-immunoreactive cells was compared to the number and location of ENK-immunoreactive cells using photographic negatives. Of 67 ENK-immunoreactive cells counted in 20 sections through L6, 54 also contained DYN immunoreactivity. Of 100 ENK-immunoreactive cells counted in 47 sections through S1, 95 also contained DYN immunoreactivity. No cells with only DYN immunoreactivity were seen. S1 was found to contain a significantly greater number (P less than 0.005) of ENK-immunoreactive cells that also contained DYN than L6. The results of these studies indicate that ENK and DYN immunoreactivities coexist in most, but not all, neurons in the DGC of L6 and S1 and that a difference exists between L6 and S1 in the extent of coexistence of these peptides. Further studies are necessary to determine if coexistence of opioids is limited only to autonomic regions of the nervous system and also to define the functional significance of this coexistence.

Localization of prodynorphin messenger rna in rat brain by in situ hybridization using a synthetic oligonucleotide probe

An in situ hybridization technique has been developed to study the distribution of messenger RNA (mRNA) encoding prodynorphin (proenkephalin B) in sections of rat brain. A 100-mer oligonucleotide was used as a template to synthesize a 32P-labelled DNA probe complementary to the coding region of rat prodynorphin mRNA. Using this probe, dense labelling was observed in the supraoptic and paraventricular nuclei of the hypothalamus, in the striatum and in the dentate gyrus. The results show for the first time the localization of prodynorphin mRNA in rat brain, and additionally demonstrate the usefulness of oligonucleotides to detect rare mRNAs by in situ hybridization.

Chronic haloperidol and clozapine differentially affect dynorphin peptides and substance P in basal ganglia of the rat

The effect of chronic neuroleptic treatment, using haloperidol or clozapine, on immunoreactive dynorphin peptide and substance P levels in basal ganglia of rats was examined. The drugs were administered i.p. in daily doses for 10 days (haloperidol 1 mg/kg and clozapine 10 mg/kg). Dynorphin A, dynorphin B and substance P were measured in substantia nigra, striatum, globus pallidus and hypothalamus using specific radioimmunoassays. The most prominent effects were observed with with clozapine which increased levels of all measured peptides in substantia nigra. Haloperidol only affected nigral substance P levels which declined, while nigral dynorphin peptide levels remained unchanged. In striatum, haloperidol slightly reduced dynorphin peptides while substance P was unaffected. Clozapine increased striatal substance P but the dynorphin peptides were not affected. Minor changes in dynorphin peptides found in globus pallidus and hypothalamus were not statistically reliable. Substance P was not changed in these structures after either of the two drugs. High molecular weight fragments (greater than or equal to 5,000) from the dynorphin precursor, proenkephalin B, were measured in substantia nigra and striatum using trypsin digestion and subsequent analysis of generated Leu-enkephalin-Arg6. These high molecular weight fragments were found to be affected in the same manner as the dynorphin peptides. This study indicates that the two types of neuroleptic drugs have different modes of interaction on peptide systems in basal ganglia of rats. Dynorphin peptides and substance P were also differentially affected.

Parkinson's disease: nigral receptor changes support peptidergic role in nigrostriatal modulation

Autoradiographic studies reveal densities of binding to somatostatin, neurotensin, mu-opiate, and benzodiazepine receptors in substantia nigra specimens from neurologically normal human brains. Binding to nigral angiotensin converting enzyme is also dense, whereas more modest densities of kappa-opiate, dopamine, and serotonin receptors are noted. In nigral specimens taken from patients with idiopathic Parkinson's disease, substantial reductions in somatostatin, neurotensin, mu-opiate and kappa-opiate receptors contrast with more modest reductions in dopamine and benzodiazepine I receptor subtypes. Angiotensin converting enzyme, serotonin, and benzodiazepine II binding are virtually unaltered. These results underscore the likelihood of strong peptidergic influences on normal and pathologically altered human nigrostriatal circuitry.

Autoradiographic localization of mu- and delta-opiate receptors in the forebrain of the rat

The autoradiographic distributions of mu opiate receptors, labeled in vitro by [125I]D-Ala2-MePhe4-Met(o)5-ol-enkephalin (FK), and delta-opiate receptors, labeled by [3H]D-Ala2-D-Leu5-enkephalin (DADLE) in the presence of oxymorphone to block high affinity binding to the mu site, were examined and compared in the forebrain of the rat. The mu- and delta-receptors were differentially distributed in most structures. mu Binding sites were found in nearly all gray matter structures and showed heterogeneous patterns of density that were correlated with cytoarchitecture and neuronal connections. Laminar density profiles were seen in laminated structures such as olfactory bulb, cerebral cortex and hippocampus. Highest mu binding densities were in striatal patches and the habenular streak. delta Sites had distinct laminar patterns in the main olfactory bulb and cortex which differed from the mu patterns. The external plexiform layer of the main olfactory bulb had the greatest density of delta binding sites; cortex and striatum were also densely labeled. The septum, globus pallidus, preoptic area and hypothalamus were lightly labeled by both ligands. The magnocellular hypothalamic nuclei had negligible mu and delta labeling. The thalamus had dense mu but sparse delta sites. mu And delta binding sites were both present in the amygdala but had different distributions. Two fiber tracts--optic tract and fasciculus retroflexus--had FK labeling. In contrast, a portion of the corpus callosum was labeled by DADLE and not by FK. The results suggest an association of mu-opiate receptors with sensory, especially olfactory, and limbic projections in the forebrain, and delta-opiate receptors with intrinsic and commissural forebrain pathways.

Distribution of dynorphin and enkephalin peptides in the rat brain

The neuroanatomical distribution of dynorphin B-like immunoreactivity (DYN-B) was studied in the adult male and female albino rat. The distribution of DYN B in colchicine- and noncolchicine-treated animals was also compared to that of another opioid peptide derived from the prodynorphin precursor dynorphin A (1-8) (DYN 1-8), and an opioid peptide derived from the proenkephalin precursor met-enkephalin-arg-gly-leu (MERGL). DYN B cell bodies were present in nonpyramidal cells of neo- and allocortices, medium-sized cells of the caudate-putamen, nucleus accumbens, lateral part of the central nucleus of the amygdala, bed nucleus of the stria terminalis, preoptic area, and in sectors of nearly every hypothalamic nucleus and area, medial pretectal area, and nucleus of the optic tract, periaqueductal gray, raphe nuclei, cuneiform nucleus, sagulum, retrorubral nucleus, peripeduncular nucleus, lateral terminal nucleus, pedunculopontine nucleus, mesencephalic trigeminal nucleus, parabigeminal nucleus, dorsal nucleus of the lateral lemniscus, lateral superior olivary nucleus, superior paraolivary nucleus, medial superior olivary nucleus, ventral nucleus of the trapezoid body, lateral dorsal tegmental nucleus, accessory trigeminal nucleus, solitary nucleus, nucleus ambiguus, paratrigeminal nucleus, area postrema, lateral reticular nucleus, and ventrolateral region of the reticular formation. Fiber systems are present that conform to many of the known output systems of these nuclei, including major descending pathways (e.g., striatonigral, striatopallidal, reticulospinal, hypothalamospinal pathways), short projection systems (e.g., mossy fibers in hippocampus, hypothalamo-hypophyseal pathways), and local circuit pathways (e.g., in cortex, hypothalamus). The distribution of MERGL was, with a few notable exceptions, in the same nuclei as DYN B. From these neuroanatomical data, it appears that the dynorphin and enkephalin peptides are strategically located in brain regions that regulate extrapyramidal motor function, cardiovascular and water balance systems, eating, sensory processing, and pain perception.

Neuronal architecture in the rat central nucleus of the amygdala: a cytological, hodological, and immunocytochemical study

The organization of neurons in the rat central nucleus of the amygdala (CNA) has been examined by using Nissl stain and immunocytochemical and retrograde tracing techniques. Four main subdivisions were identified on the basis of quantitative analyses of Nissl-stained material: medial (CM), lateral (CL), lateral capsular (CLC), and ventral (CV). An intermediate subdivision (CI), previously described by McDonald ('82), was apparent only in animals that had HRP-WGA injected into the bed nucleus of the stria terminalis. Large populations of neurotensin-, corticotropin-releasing factor (CRF)-, and enkephalin-immunoreactive neurons were present within the lateral divisions (mainly CL), although they were also seen within CM. Somatostatin-immunoreactive neurons were distributed mainly within CL and CM. Within CL, neurotensin- and enkephalin-immunoreactive neurons were more numerous laterally whereas CRF- and somatostatin-immunoreactive neurons were more numerous medially. Substance P-immunoreactive neurons were almost exclusively confined to CM. Only a few cholecystokinin- and vasoactive-polypeptide-immunoreactive neurons were seen in the CNA, and they were observed within CL, CV, and CM. The majority of neurons projecting to the dorsal medulla, hypothalamus, and ventral tegmental area were located within CM, although a significant number of cells were also seen within CL. Efferent projections to the bed nucleus of the stria terminalis were found to arise from neurons located within all subdivisions of the CNA. Thus, the distributional patterns of peptidergic and efferent neurons were not confined to individual cytoarchitectonically- defined subdivisions of the CNA. Rather, the results suggest overlapping medial to the lateral trends. Comparisons with the results of previous studies indicate that peptidergic and afferent terminal distribution patterns are more restricted to individual cytoarchitectonically defined subregions of the CNA. These observations suggest that the detailed cytoarchitecture of the CNA more likely reflects the functional integration of afferents rather than the organization of the CNA output neurons.

Further characterization of the extra-arcuate alpha-melanocyte stimulating hormone-like material in hypothalamus: biochemical and anatomical studies

Previous studies had shown the existence of an extra-arcuate cell group in lateral hypothalamus which contains alpha-melanocyte stimulating hormone (a-MSH)-like immunoreactivity, but no other pro-opiomelanocortin (POMC) immunoreactivity. The question we have attempted to address in this series of studies is whether the material is indeed a-MSH or a cross-reacting material. Chromatographic studies failed to detect any material which is different from a-MSH or des-acetyl-a-MSH, suggesting that either the material is authentic a-MSH/des-acetyl-a-MSH, or that it is not detected by our RIAs. A series of manipulations including dissections of arcuate vs. extra-arcuate hypothalamic areas, treatment with colchicine, lesions with monosodium glutamate and knife cuts were aimed at isolating the extra-arcuate region and showing that it contains an excess of a-MSH over beta-endorphin (B-END), presumably deriving from the extra-arcuate group. However, all studies showed parallel changes in a-MSH and B-END, suggesting that we were not detecting a non-POMC derived a-MSH in these studies. This led to the tentative conclusion that the material was not a-MSH and was not being detected by our RIA's. This hypothesis was tested by further characterizing the material immunohistochemically. These studies led to the conclusion that the extra-arcuate material had a carboxy-terminal homology with a-MSH but differed from it in the midregion, since antisera directed at the 4-10 region of a-MSH failed to stain this non-POMC cell group. Finally, the anatomy of this extra-arcuate group is described, particularly the projections to the striatum, hippocampus, neocortex and olfactory bulb.

Effect of discrete brain lesions on hypothalamic and pituitary immunoreactive dynorphin

Radiofrequency lesions of the anterior hypothalamic area reduced immunoreactive dynorphin (ir-DYN) in the hypothalamus and in the neurointermediate lobe of the pituitary. Ablation of the medial preoptic area was not associated with any significant modification of ir-DYN in the tissue examined. Destruction of the medial basal hypothalamus in parallel lowered ir-DYN in the hypothalamus and in both pituitary lobes. Neonatal administration of monosodium glutamate had no significant effect on ir-DYN. These findings indicate that changes of ir-DYN in the hypothalamus and pituitary are associated with the destruction of anatomically and functionally distinct neural systems.

Comparison of the substance P- and dynorphin-containing projections to the substantia nigra: a radioimmunocytochemical and biochemical study

A series of knife cuts were made in the striatonigral pathway and changes in dynorphin B (Dyn) and substance P (SP) input to the substantia nigra were examined using radiolabeled antibodies and radioimmunoassay (RIA). Cryostat cut sections were incubated with primary antibody followed by a secondary antibody labeled with 125I. Apposition of the radiolabeled sections to LKB Ultrofilm generated an image that was qualified by computerized optical densitometry. The striatonigral system served as a model system for comparing the quantitative capabilities of radioimmunocytochemistry with RIA. The results indicated a strong correlation between optical densitometry measurements and RIA for both Dyn (r = 0.97) and SP (r = 0.98) antisera. This suggests that radioimmunocytochemistry may be used for quantitative, as well as, qualitative descriptions of the distribution of tissue antigens. Knife cuts separating the rostral caudate putamen from the substantia nigra resulted in less than 40% depletion of dynorphin and substance P in the nigra pars reticulata, leaving the levels of both peptides relatively unchanged in the pars lateralis. More caudal knife cuts resulted in progressively greater depletions of both peptides in the pars reticulata and pars lateralis.

An autoradiographic study of projections ascending from the midbrain central gray, and from the region lateral to it, in the rat

Ascending projections from the midbrain central gray (CG) and from the region lateral to it were traced in the rat using tritiated amino acid autoradiography. Leucine or a cocktail of amino acids (leucine, proline, lysine, histidine, and tyrosine) were used as tracers. In addition to projections within the midbrain, ascending fibers follow three trajectories. The ventral projection passes through the ventral tegmental region of Tsai and the medial forebrain bundle to reach the hypothalamus, preoptic area, caudoputamen, substantia innominata, stria terminalis, and amygdala. There are labeled fibers in the diagonal bands of Broca and medial septum, and terminal labeling in the lateral septum, nucleus accumbens, olfactory tubercle, and frontal cortex. The dorsal periventricular projection terminates in the midline and intralaminar thalamic nuclei. The ventral periventricular projection follows the ventral component of the third ventricle into the hypothalamus, passing primarily through the dorsal hypothalamic area and labeling the rostral hypothalamus and preoptic area. Projections from the region lateral to the CG are similar, but exhibit stronger proximal, and weaker distal, projections. Rostral levels of the CG send heavier projections to the fields of Forel and the zona incerta, but fewer fibers through the supraoptic decussation, than do caudal levels. Ascending projections from the CG are both strong and widespread. Strong projections to the limbic system and the intralaminar thalamic nuclei provide an anatomical substrate for CG involvement in nociception and affective responses.

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

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