Colocalization of alpha-neo-endorphin and dynorphin immunoreactivity in hypothalamic neurons

kappa-Opioid receptor signaling and brain reward function

The dynorphin-like peptides have profound effects on the state of the brain reward system and human and animal behavior. The dynorphin-like peptides affect locomotor activity, food intake, sexual behavior, anxiety-like behavior, and drug intake. Stimulation of kappa-opioid receptors, the endogenous receptor for the dynorphin-like peptides, inhibits dopamine release in the striatum (nucleus accumbens and caudate putamen) and induces a negative mood state in humans and animals. The administration of drugs of abuse increases the release of dopamine in the striatum and mediates the concomitant release of dynorphin-like peptides in this brain region. The reviewed studies suggest that chronic drug intake leads to an upregulation of the brain dynorphin system in the striatum and in particular in the dorsal part of the striatum/caudate putamen. This might inhibit drug-induced dopamine release and provide protection against the neurotoxic effects of high dopamine levels. After the discontinuation of chronic drug intake these neuroadaptations remain unopposed which has been suggested to contribute to the negative emotional state associated with drug withdrawal and increased drug intake. kappa-Opioid receptor agonists have also been shown to inhibit calcium channels. Calcium channel inhibitors have antidepressant-like effects and inhibit the release of norepinephrine. This might explain that in some studies kappa-opioid receptor agonists attenuate nicotine and opioid withdrawal symptomatology. A better understanding of the role of dynorphins in the regulation of brain reward function might contribute to the development of novel treatments for mood disorders and other disorders that stem from a dysregulation of the brain reward system.

The dynorphin/kappa opioid system as a modulator of stress-induced and pro-addictive behaviors

Stress is a complex experience that carries both aversive and motivating properties. Chronic stress causes an increase in the risk of depression, is well known to increase relapse of drug seeking behavior, and can adversely impact health. Several brain systems have been demonstrated to be critical in mediating the negative affect associated with stress, and recent evidence directly links the actions of the endogenous opioid neuropeptide dynorphin in modulating mood and increasing the rewarding effects of abused drugs. These results suggest that activation of the dynorphin/kappa opioid receptor (KOR) system is likely to play a major role in the pro-addictive effects of stress. This review explores the relationship between dynorphin and corticotropin-releasing factor (CRF) in the induction of dysphoria, the potentiation of drug seeking, and stress-induced reinstatement. We also provide an overview of the signal transduction events responsible for CRF and dynorphin/KOR-dependent behaviors. Understanding the recent work linking activation of CRF and dynorphin/KOR systems and their specific roles in brain stress systems and behavioral models of addiction provides novel insight to neuropeptide systems that regulate affective state.

New pharmacologic approaches to the prevention of space/motion sickness

Fundamental approaches in selection of new agents for evaluation in prevention of space/motion sickness (SMS) are reviewed. The discussion centers on drugs under investigation at the Johnson Space Center. Methodology that employs the rotating chair for measuring SMS symptomatology and susceptibility is described. The most obvious approach to the development of new agents relies on selection of agents from drug classes that possess pharmacologic properties of established anti-motion sickness agents. A second approach selects drugs that are used to prevent emesis caused by means other than exposure to motion. The third approach relies on basic research that characterizes individual differences in susceptibility. The hypothesis is: detection of individual differences leads to identification of specific drugs, which target physiologic systems that show individual differences. These physiologic systems are targets for therapy and may play a role in the etiology of SMS. Two drugs that reduce susceptibility to SMS include dexamethasone and d(CH2)5Tyr(Me)AVP, a vasopressin (AVP)V1 antagonist. The latter peptide has demonstrated complete blockade of emesis and other significant symptoms in squirrel monkeys. These studies were predicated on observations that subjects who were more resistant to SMS had higher plasma AVP after severe nausea than subjects with lower resistances. Investigations are underway to test a 0.5-mg intravenous dose in humans. Kappa opioid agonists inhibit AVP release and offer new therapeutic possibilities and advantages over AVP peptides. This review details the experimental data collected on AVP and adrenocorticotropin. The literature supports interrelated roles for AVP and opioid peptides in SMS. Experimental testing of kappa agonists is warranted because specific opioid agonists act at neuroanatomical sites causing nausea and vomiting. It is argued opioid receptors in the chemoreceptor trigger zone and vomiting center stimulate and inhibit the emetic response, respectively. The evidence suggests kappa and/or mu receptors at VC are involved in inhibition of emesis, whereas delta opioid receptors at CTZ are involved in stimulation of emesis.

Localization of chemical messengers in magnocellular neurons of the hypothalamic supraoptic and paraventricular nuclei: an immunohistochemical study using experimental manipulations

Indirect immunofluorescence histochemistry was used to investigate the distribution and extent of co-localization of chemical messengers in magnocellular neurons of the supraoptic and paraventricular nuclei. In order to increase the number of neurons immunoreactive to the antisera used, experimental manipulations were employed. The homozygous Brattleboro (diabetes insipidus) rat was also investigated. In untreated rats, only vasopressin- and oxytocin-like immunoreactivities could be observed. Colchicine treatment alone resulted in appearance of galanin-, dynorphin-, cholecystokinin-, [Leu]enkephalin- and thyrotropin-releasing hormone-positive cells. In hypophysectomized rats, all these markers, except tyrosine hydroxylase, showed substantial further increases. In addition, peptide histidine-isoleucine-immunoreactive cell bodies could now be seen. After salt-loading alone, tyrosine hydroxylase-like immunoreactivity was markedly increased, whereas vasopressin- and oxytocin-like immunoreactivity were very weak or undetectable. When salt-loaded rats received colchicine, corticotropin-releasing factor- and peptide histidine-isoleucine-like immunoreactivity in addition increased, whereas galanin- and dynorphin-like immunoreactivity markedly decreased. The Brattleboro rats resembled untreated rats, except their lack of vasopressin-like immunoreactivity, the marked increase in tyrosine hydroxylase-like immunoreactivity, and smaller increase in galanin- and dynorphin-like immunoreactivity. Addition of colchicine to Brattleboro rats resulted in some distinct further changes in that dynorphin-like immunoreactivity decreased in some neurons and that [Leu]enkephalin-, corticotropin-releasing factor- and peptide histidine-isoleucine-like immunoreactivity increased substantially. Several similarities could be observed between the salt-loaded and Brattleboro rats, with or without colchicine. However, a marked difference in immunoreactive [Leu]enkephalin levels was observed with no difference in dynorphin-like immunoreactivity, and opposite changes in galanin-like immunoreactivity. The results confirm the traditional view that hypothalamic magnocellular neurons in the supraoptic and paraventricular nuclei contain two separate cell populations, characterized by vasopressin and oxytocin, respectively, and that they contain additional messenger molecules in specific patterns. Vasopressin-containing neurons primarily express tyrosine hydroxylase, galanin, dynorphin, [Leu]enkephalin and peptide histidine-isoleucine, and to a minor extent cholecystokinin and thyrotropin-releasing hormone. Oxytocin-containing neurons mainly have cholecystokinin and corticotropin-releasing factor, and to a minor extent galanin, dynorphin, [Leu]enkephalin and thyrotropin-releasing hormone. Furthermore, our results detail individual co-existence situations among these putative messenger molecules. Thus, magnocellular neurons respond in a differential way to various stimuli and they store multiple bioactive substances in specific combinations.

Alpha-neo-endorphin coexists with dynorphin-A(1-8) within intramurally lying perikarya of rat duodenum

By the use of the immunofluorescent microscopic staining technique, adjacent serial sections through the rat duodenum were alternately stained with specific antisera directed to the opioid peptides alpha-neo-endorphin and dynorphin-A(1-8). alpha-Neo-endorphin immunoreactivity has been revealed exclusively within perikarya lying intramurally in the longitudinal muscle layer. These alpha-neo-endorphin and dynorphin-A(1-8) immunoreactive perikarya were large in diameter, round in shape, contained a large and round nucleus, and were recognized only occasionally there. alpha-Neo-endorphin immunoreactivity was coexistent with dynorphin-A(1-8)-positive material within these perikarya. Since no alpha-neo-endorphin material was detected within duodenal nerve fibres and terminals, it might be concluded that this peptide is further enzymatically cleaved to the opioid pentapeptide Leu-enkephalin during its axonal transport from intramural perikarya to nerve terminals and during its storage there.

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

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

Co-existence of cholecystokinin- or gastrin-like peptides with other peptides in the hypophysis and the hypothalamus

The presence of cholecystokinin and gastrin has been reported in the hypothalamohypophyseal system. These peptides present a peculiar distribution in the hypothalamic nuclei, the median eminence, and the neurohypophysis. CCK and gastrin have close relationships with other peptides like oxytocin, CRF, vasopressin, and the enkephalins; these relationships vary in different projecting areas and in different types of hypothalamic neurons. The functional role of G-CCK in neurosecretion seems to be linked to the role of these closely associated peptides and certainly deserves further investigation.

Sequence and expression of the rat prodynorphin gene

We report here the isolation of a lambda genomic clone that contains the nucleotide sequence coding for the main exon of the rat prodynorphin (proenkephalin B) gene. This exon codes for the majority of the translated region of prodynorphin mRNA including the opioid peptides alpha-neo-endorphin, dynorphin A, and dynorphin B. The entire 3' untranslated region is also contained on the lambda clone. Nucleotide sequence comparison with the main exon of the human prodynorphin gene reveals both structural and sequence homology. RNA blot analysis reveals that prodynorphin transcripts can be seen in numerous regions of the rat brain and in the adrenal gland, spinal cord, testis, and anterior pituitary.

Localization of dynorphin B-like and alpha-neoendorphin-like immunoreactivities in the guinea pig organ of Corti

Antiserum to dynorphin B and antiserum to alpha-neoendorphin were used in an immunocytochemical examination of the guinea pig organ of Corti. Immunoreactive staining for these two proenkephalin B (prodynorphin)-derived peptides was seen in the lateral system of olivocochlear efferents in the organ of Corti: the inner spiral bundle, the tunnel spiral bundle and by the bases of inner hair cells. Immunoreactive staining with both antisera was also seen in efferent terminals on outer hair cells at or above the level of the nucleus, which may represent terminals of either the lateral or the medial system. No immunoreactive staining was seen in tunnel crossing fibers and at bases of outer hair cells corresponding to the medial system of efferents. The staining seen with antiserum to dynorphin B and to alpha-neoendorphin has similar distribution to that seen with antisera to methionine enkephalin; there may be co-localization of these neuropeptides in the lateral system of efferents. Choline acetyltransferase-like immunoreactivity (co-localized with enkephalin-like immunoreactivity in the lateral system in the brainstem) and glutamic acid decarboxylase (GAD)-like immunoreactivity have also been found in olivocochlear efferents. Further studies will be necessary to determine if the dynorphins are co-localized with other neurotransmitter candidates and what their interactions may be.

Opioid biology: the next set of questions

A range of biologically different opioid peptides are synthesised as components of three distinct precursors, pro-opiomelanocortin, proenkephalin, and prodynorphin. They interact with a number of receptors which have so far been characterised as mu, delta, kappa, sigma, and epsilon. It is unclear which ligands bind to which receptors under physiological circumstances, but preferential in vitro interactions include enkephalins with delta receptors, dynorphin with kappa receptors, and beta-endorphin with epsilon receptors. Post-translational processing determines which of several opioid products are produced from each precursor, but the identity of the enzymes involved and regulation of processing is unknown. Opioid involvement in the neuroendocrine and cardiovascular systems is reviewed. Naloxone-sensitive opioid mechanisms are implicated in the control of gonadotrophin and adrenocorticotropic hormone secretion and in the hypotension of various types of shock. The investigation of possible dynorphin involvement in neurohypophysial function is taking place because vasopressin and dynorphin A (1-8) have been shown to coexist in the neurosecretory vesicles of magnocellular neurons.

Steady state levels of pro-dynorphin-related end products in the striatum and substantia nigra of the adult rhesus monkey

Analysis of an acid extract of the striatum of the rhesus monkey revealed that the molar ratio of dynorphin A(1-8)-sized material and dynorphin (A(1-17)-sized material is approximately 1:1. In addition, the molar ratios of the dynorphin A-related end products to both dynorphin B(1-13)-sized material and alpha-neo-endorphin-sized material were approximately 1:1. Fractionation of an acid extract of the substantia nigra by gel filtration and reverse phase HPLC revealed the following molar ratios for pro-dynorphin-related end products. The molar ratio of dynorphin A(1-8) to dynorphin A(1-17) is approximately 6:1. The molar ratios of dynorphin A-related end products to dynorphin B(1-13) and alpha-neo-endorphin were approximately 0.5 and 0.8, respectively. Comparisons between proteolytic processing patterns of pro-dynorphin in the striatum and the substantia nigra of the rhesus monkey are considered. In addition, comparisons between pro-dynorphin processing in the substantia nigra of the rhesus monkey and the substantia nigra of the rat are discussed.

Prodynorphin peptide immunocytochemistry in rhesus monkey brain

The present study describes the immunocytochemical distribution of peptides derived from the prodynorphin precursor in the brain of the rhesus monkey (Macaca mulatta). Animals were treated with colchicine (intracerebroventricularly) prior to perfusion to enhance the observation of perikaryal immunoreactivity. Using antisera generated against dynorphin A(1-17), dynorphin B(1-13), and prodynorphin(186-208) (or bridge peptide), the anatomical distribution of dynorphin systems was mapped. The results indicate a widespread neuronal localization of immunoreactivity from the cerebral cortex to the caudal medulla. Anti-dynorphin B and anti-bridge peptide sera proved useful for the demonstration of neuronal perikarya, while the dynorphin A antiserum was best for localizing terminal projection fields. Immunoreactive perikarya are located in numerous brain loci, including the cingulate cortex, caudate nucleus, amygdala, hypothalamus (especially the magnocellular nuclei), thalamus, substantia grisea centralis, parabrachial nucleus, nucleus tractus solitarius, and other nuclei. In addition, fiber and terminal immunoreactivity are seen in varying densities in the striatum and pallidum, substantia innominata, hypothalamus, substantia nigra pars reticulata, parabrachial nucleus, spinal trigeminal nucleus, and other areas. The distribution of prodynorphin peptides in the brain of the monkey is similar to that described for the rat brain; however, significant differences also exist. Other interspecies differences in the anatomy of prodynorphin and proenkephalin neuronal systems in the monkey and human brain are further discussed.

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

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

Subcellular distribution of opioid peptides in rat hypothalamus and pituitary

Homogenates of rat anterior lobe (AL) and neurointermediate lobe (NIL) pituitary and rat hypothalamus were subjected to subcellular fractionation and density gradient centrifugation. The subcellular distribution of immunoreactive dynorophin A (ir-Dyn A) in NIL was found to be similar to that of ir-arginine vasopressin (ir-AVP). ir-Dyn A migrated as a discrete band on sucrose density gradients, which corresponded in sedimentation rate to that of ir-AVP, suggesting that these two peptides are stored within organelles of similar size and density. Two other products of prodynorphin, ir-alpha-neoendorphin (ir-alpha-nEND) and ir-Dyn A-(1-8) also comigrated with ir-AVP. ir-[Leu5]-enkephalin (ir-LE), which may be a product of prodynorphin or proenkephalin, was also found to migrate in this region of the gradient. When a homogenate of rat hypothalamus was prepared using a method that has been developed for synaptosome isolation, ir-Dyn A was found to comigrate with Na+/K+-activated adenosine triphosphatase (Na/K-ATPase), a synaptosomal marker enzyme. Using a more concentrated homogenate ir-Dyn A was found to migrate to a less dense region where peptide-containing synaptic vesicles have previously been localized. When a synaptosomal preparation was lysed in hypotonic solution a shift was seen in the migration rate of ir-Dyn A to this region of the gradient (containing putative synaptic vesicles). Thus the bulk of hypothalamic dynorphin appears to be present within synaptosome-like structures which, upon lysis, release a less dense, smaller subcellular organelle corresponding in sedimentation characteristics to other types of peptide-containing synaptic vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracerebral injection of different antibodies against endogenous opioids suggests alpha-neoendorphin participation in control of feeding behaviour

The mechanism of feeding behaviour of rats was examined. We used antibodies to different opioid peptides in order to reduce the tonic activity of various endogenous opioid peptide systems that may underly appetite. Unilateral microinjection of anti-alpha-neoendorphin antibodies into various areas of the ventromedial hypothalamus (VMH) inhibited food and water intake up to 45% in deprived animals. Injections outside this area failed to affect feeding. Administration of anti-beta-endorphin antibodies into the VMH moderately attenuated appetite. A considerable decrease of food and water intake was observed only upon injection of this antibody into the nucleus periventricularis hypothalami, a region generally believed to be involved with feeding. A marginal reduction of appetite was observed with anti-dynorphin antibodies injected into the VMH. These data may suggest that alpha-neoendorphin is involved in the control of food and water intake in the VMH.

Vasopressin release by D-aspartic acid, morphine and prolyl-leucyl-glycinamide (PLG) in DI Brattleboro rats

The L-asparaginase activities of the brains of the Wistar, heterozygous and homozygous Brattleboro rats divided into three parts namely the anterior, middle and posterior which respectively contained cerebral cortex, hippocampus + midbrain + thalamus + hypothalamus cerebellum + pons + medulla oblongata were estimated. The L-asparaginase activities of all the three parts in the homozygous Brattleboro rats were significantly higher than in the Wistar rats as well as in the heterozygous Brattleboro rats. Twenty min following the injections of 200 mg/kg D-aspartic acid, 20 mg/kg morphine, 200 mg/kg D-aspartic acid + 20 mg/kg morphine, 6 mg/kg prolyl-leucyl-glycinamide (PLG) and 6 mg/kg PLG + 20 mg/kg morphine the L-asparaginase activities of all three parts of the homozygous Brattleboro rat brains were found to be significantly inhibited. After having seen the suppressive effect of the drugs and their combinations used before the homozygous Brattleboro rats were given D-aspartic acid, morphine, D-aspartic acid + morphine, PLG and PLG + morphine for seven days. Then their plasma vasopressin levels were determined by RIA. The treatments applied to the homozygous Brattleboro rats caused the appearance of a significant amount vasopressin in the plasma. The results were interpreted as evidence for the fact that the inhibition of the brain L-asparaginase provides and/or accelerates the biosynthesis and/or release of vasopressin. As morphine has a vasopressin releasing and a brain L-asparaginase inhibiting effect the antidiuretic action of morphine was considered to be linked to its inhibitory effect on the brain L-asparaginase.

Neuropeptides in the hypothalamo-hypophyseal system: lateral retrochiasmatic area as a common gate for neuronal fibers towards the median eminence

The source and topography of neuropeptide-containing axons in the median eminence are summarized. Several of these neuropeptide-containing neurons (thyrotropin-releasing hormone, corticotropin-releasing hormone, vasopressin, oxytocin, cholecystokinin) are localized in the paraventricular nucleus. The periventricular and medial preoptic nuclei constitute the main sources of somatostatin and luteinizing hormone releasing hormone axons in the median eminence, respectively. Dynorphins and alpha-neo-endorphin-synthetizing neurons in the supraoptic nucleus also project to the median eminence. Wherever they originate, the projections may follow a common organization pattern and use a common gate--the lateral retrochiasmatic area--to enter the median eminence.

Immunoreactive dynorphin and alpha-neo-endorphin in rat hypothalamo-neurohypophyseal system

Concentrations of dynorphin and alpha-neo-endorphin were measured in rat supraoptic and paraventricular nuclei, median eminence and posterior pituitary. Paraventricular lesions did not alter the level of either peptide in the median eminence or posterior pituitary. Knife cuts in the lateral retrochiasmatic area that severed the supraoptico-hypophyseal tract reduced dynorphin and alpha-neo-endorphin levels by 64-80% in the posterior pituitary and by somewhat less in the median eminence. Knife cuts in the vicinity of the supraoptic nucleus that did not interrupt the supraoptico-hypophyseal tract did not affect peptide concentrations in the posterior pituitary. Our data suggest that dynorphin and alpha-neo-endorphin in the posterior pituitary are in processes of supraoptic nucleus neurons. These neurons also project to the median eminence which may receive fibers from other dynorphin and alpha-neo-endorphin containing cells too.

Monoclonal antibody to the message sequence Tyr-Gly-Gly-Phe of opioid peptides exhibits the specificity requirements of mammalian opioid receptors

Six myeloma cell hybrids producing antibodies to human beta-endorphin were isolated from a single mouse spleen. The monoclonal antibodies displayed different binding patterns with the antigen. We report the characterization of one antibody which recognizes the tetrapeptide Tyr-Gly-Gly-Phe representing the message sequence found at the NH2 terminus of all naturally occurring mammalian opioid peptides. Competition experiments in radioimmunoassay and immunohistochemistry show that the antibody fails to bind the beta-endorphin precursor beta-lipotrophin, does not discriminate among opioid peptides that share the same message sequence but have different COOH-terminal extensions, and does not react with pharmacologically inactive derivatives of beta-endorphin. The antibody recognition of the message sequence of natural opioid peptides is sensitive to those molecular changes that affect their receptor binding competence.

Immunohistochemical distribution of dynorphin B in rat brain: relation to dynorphin A and alpha-neo-endorphin systems

A specific antiserum was prepared against dynorphin B, an endogenous opioid peptide contained in a recently isolated 4,000-dalton dynorphin. The antiserum did not crossreact with dynorphin A, alpha-neo-endorphin, beta-neo-endorphin, dynorphin-(1-8), or [Leu]enkephalin. In immunohistochemical staining experiments on frozen sections through rat brains from normal and colchicine-treated animals, the antiserum labeled the same neuronal fiber systems previously described as containing both dynorphin A and alpha-neo-endorphin immunoreactive material. The alpha-neo-endorphin/dynorphin A immunoreactive perikarya in the hypothalamic magnocellular nuclei also were labeled by the dynorphin B antiserum. In addition, the dynorphin B antiserum revealed groups of immunoreactive neuronal cell bodies in several other hypothalamic and extrahypothalamic areas, including brain-stem, midbrain, central nucleus of amygdala, and in the dorsomedial, lateral, and anterior nuclei of hypothalamus. These perikarya had not been detected in previous studies that used dynorphin A and alpha-neo-endorphin antisera. The findings are in agreement with recent studies demonstrating a common precursor for dynorphin A, dynorphin B, and alpha-neo-endorphin. The apparently wider distribution of dynorphin B immunoreactive cell bodies compared to alpha-neo-endorphin/dynorphin A immunoreactive perikarya may be a reflection of differential processing of the precursor in different brain regions.

Pro-dynorphin peptides are found in the same neurons throughout rat brain: immunocytochemical study

It is known that the opioid peptide dynorphin A has a broad distribution throughout the neuraxis. Recent biochemical studies have extended the sequence of dynorphin A by 15 amino acids to include another [Leu]enkephalin-containing peptide known as dynorphin B. These sequence data have been validated by the elucidation of the structure of the hypothalamic mRNA coding for alpha- and beta-neo-endorphin, dynorphin A, and dynorphin B. Using specific antisera directed against each of the three opioid peptides, we have studied their cellular distribution in rat brain. Their distribution patterns are extremely similar, if not identical. Furthermore, all three peptide immunoreactivities can be localized to the same cells in five nuclear groups throughout the brainstem--the supraoptic nucleus, the paraventricular nucleus, a group of cells in the lateral hypothalamic area, the nucleus parabrachialis, and the nucleus tractus solitarius. The sequence of a common precursor for dynorphin A, B, and alpha- and beta-neo-endorphin was deduced from hypothalamic mRNA. The ability to localize all three peptides together within cells in widely placed nuclei strongly supports the use of the same biosynthetic precursor for the neo-endorphin and dynorphin peptides in other parts of the central nervous system as well.

Immunoreactive dynorphin-(1-8) and corticotropin- releasing factor in subpopulation of hypothalamic neurons

Immunoreactive corticotropin-releasing factor (CRF) and dynorphin-(I-8) were visualized in rat hypothalamus by immunohistofluorescence with specific antibodies. In brains from colchicine-treated, adrenalectomized rats, neuronal perikarya with immunoreactive CRF were observed in the paraventricular nucleus of the hypothalamus. The CRF occurred together with the dynorphin-(1-8). However, the CRF immunoreactivity occurred only in a subpopulation of the dynorphin-(1-8) immunoreactive cells. These findings suggest that there may be a functional interrelationship of CRF with dynorphin-related opioid peptides and provide further evidence that neurons may contain more than one bioactive substance.

Comparison of the distribution of dynorphin systems and enkephalin systems in brain

A study of the anatomical distribution of the endogenous opioid dynorphin in rat brain showed that the peptide is localized in a widespread system with multiple cell groups and projections. This network is revealed by the use of multiple antiserums against dynorphin and can be distinguished from the system containing methionine-enkephalin and leucine-enkephalin, which is mapped by the use of antiserums against the enkephalins and biosynthetically related peptides in the adrenal. It thus appears that the brain contains at least three separate opioid neuronal networks: an enkephalin family with components similar to those found in the adrenal, a beta-endorphin family, and a dynorphin family.

Dynorphin immunocytochemistry in the rat central nervous system

The distribution of dynorphin in the central nervous system was investigated in rats pretreated with relatively high doses (300-400 micrograms) of colchicine administered intracerebroventricularly. To circumvent the problems of antibody cross-reactivity, antisera were generated against different portions as well as the full dynorphin molecule (i.e., residues 1-13, 7-17, or 1-17). For comparison, antisera to [Leu]enkephalin (residues 1-5) were also utilized. Dynorphin was found to be widely distributed throughout the neuraxis. Immunoreactive neuronal perikarya exist in hypothalamic magnocellular nuclei, periaqueductal gray, scattered reticular formation sites, and other brain stem nuclei, as well as in spinal cord. Additionally, dynorphin-positive fibers or terminals occur in the cerebral cortex, olfactory bulb, nucleus accumbens, caudate-putamen, globus pallidus, hypothalamus, substantia nigra, periaqueductal gray, many brain stem sites, and the spinal cord. In many areas studied, dynorphin and enkephalin appeared to form parallel but probably separate anatomical systems. The results suggest that dynorphin occurs in neuronal systems that are immunocytochemically distinct from those containing other opioid peptides.

Endogenous opiates: 1981

This paper is the fourth of an annual series reviewing the research concerning the endogenous opiate peptides. This installment covers only work published during 1981 and attempts to provide a comprehensive, but not exhaustive, survey of the area. Previous papers in the series have dealt with research done before 1981. Topics concerning endogenous opiates reviewed here include a delineation of their receptors, their distribution, their precursors and degradation, behavioral effects resulting from their administration, their possible involvement in physiological responses, and their interactions with other peptides and hormones. Due to the burgeoning literature in this field, the comprehensive nature of this review in the future will be limited to considerations of behavioral phenomena related to the endogenous opiates.

Rimorphin, a unique, naturally occurring [Leu]enkephalin-containing peptide found in association with dynorphin and alpha-neo-endorphin

The tridecapeptide NH2-Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr-COOH has been purified from extracts of bovine posterior pituitary glands. This unique peptide, which has been given the name "rimorphin," is a major [Leu]enkephalin-containing peptide in all tissues examined that contain dynorphin and alpha-neo-endorphin. However, except for the initial hexapeptide sequence, it is structurally unrelated to the other two peptides.

Immunohistochemical localization of dynorphin (1-8) in hypothalamic magnocellular neurons: evidence for absence of proenkephalin

Dynorphin(1-8) immunoreactivity was visualized by immunohistofluorescence in hypothalamic magnocellular neurons of the rat. No immunoreactive met-enkephalin-Arg6-Gly7-Leu8, a fragment of the adrenal medulla pro-enkephalin molecule, was detected in magnocellular neurons. However, a strong met-enkephalin-Arg6-Gly7-Leu8-like immunostaining was seen in other regions of the brain. These results suggest that in magnocellular neurons dynorphin(1-8) exists independently from pro-enkephalin and therefore the magnocellular neurons represent a third opioid peptide neuronal system in brain. These observations, however, do not rule out a coexistence of proenkephalin and dynorphin-related peptides in other regions of the brain.

Dynorphin is located throughout the CNS and is often co-localized with alpha-neo-endorphin

The opioid peptide dynorphin has been described as widely distributed in CNS when measured by RIA. Our previous immunohistochemical studies have only demonstrated dynorphin cells as those containing AVP. We now report the specific localization of dynorphin throughout the neuraxis. Further, dynorphin and alpha-neo-endorphin have been co-localized to the same magnocellular neurosecretory cells in hypothalamus. We report agreement with the findings of others and extend them to include a cell group in dorsomedial hypothalamus, further strengthening the association between dynorphin and alpha-neo-endorphin.

Leucine-enkephalin-like immunoreactivity in vasopressin terminals is enhanced by treatment with peptidases

When sections through rat neurohypophyses were treated with trypsin prior to incubation with enkephalin antibodies, vasopressin terminals invariably exhibited leucine-enkephalin-like immunoreactivity. Omitting tryptic cleavage the vasopressin terminals of some specimens only were immunostained. The enkephalin-like material was contained in the neurosecretory granules as shown by the protein A gold and the peroxidase anti-peroxidase method. We assume that the leucine-enkephalin sequence in vasopressin endings to some extent is present in a precursor form, possibly as dynorphin or alpha-neo-endorphin, from which the pentapeptide is liberated by enzymatic cleavage.

Hypothalamo-posterior pituitary system in Brattleboro rats: immunoreactive levels of leucine-enkephalin, dynorphin (1-17), dynorphin (1-8) and alpha-neo-endorphin

The levels of immunoreactive leucine-enkephalin, alpha-neo-endorphin, dynorphin (1-17) and dynorphin (1-8) have been determined in the hypothalamus and posterior pituitary from male and female Brattleboro rats homozygous (unable to produce vasopressin) and heterozygous (producing vasopressin) for diabetes insipidus, and from male and female Long Evans rats. In the hypothalamus we found no significant differences in the levels of these peptides while there were great differences in extracts from the posterior pituitary: female homozygous animals have greatly reduced levels in all four peptides compared to the heterozygous controls. In male homozygous animals the differences in the dynorphin (1-17) and leucine-enkephalin levels were small whereas the concentrations of alpha-neo-endorphin and dynorphin (1-8) showed a significant decrease compared to the male heterozygous controls. The results indicate a reduction in opioid peptides linked to the vasopressin deficiency in a partially sex dependent manner.

Immunohistochemical distribution of alpha-neo-endorphin/dynorphin neuronal systems in rat brain: evidence for colocalization

alpha-Neo-endorphin and dynorphin immunoreactivities in rat brain were visualized by double antibody immunofluorescence of frozen sections. Antibodies were used that were specific for their respective antigens. The pattern of neuronal immunostaining produced by alpha-neo-endorphin and dynorphin antisera in adjacent serial sections was completely superimposible. No areas were found in which alpha-neo-endorphin or dynorphin immunoreactivities existed alone. The following brain regions contained alpha-neo-endorphin/dynorphin-immunoreactive fibers and terminals: the median forebrain bundle, the internal capsule, the substantia nigra, the hypothalamus, the nucleus accumbens, the hippocampus, and the medulla oblongata. A few fibers were seen in the cerebral cortex and in the corpus striatum. In many regions, this neuronal fiber system seems to overlap the neuronal system previously described to contain [Met]-/[Leu]enkephalin-immunoreactive material. In brains from colchicine-treated animals, numerous alpha-neo-endorphin/dynorphin-immunoreactive neuronal cell bodies were seen in the supraoptic, retrochiasmatic supraoptic, paraventricular, and magnocellular accessory nuclei of the hypothalamus. It is concluded that alpha-neo-endorphin-like and dynorphin-like immunoreactivities are part of the same neuronal system.

Enzymatic cleavage prior to antibody incubation as a method for neuropeptide immunocytochemistry

When deplasticized Epon sections were treated with endo- and/or exopeptidases prior to incubation with antibodies, the neuropeptide immuno-reactivity of secretory nerves was often altered in a predictable way. Cleavage of neurosecretory material in octopus nerves by trypsin and carboxypeptidase-B enhanced enkephalin-like immunoreactivity, while Molluscan neuropeptide-like immunoreactivity was prevented by tryptic cleavage. The enzyme effects indicated the occurrence of a heptapeptide (Tyr-Gly-Gly-Phe-Met/Leu-Arg-Phe) that contains both the enkephalin and the Molluscan neuropeptide sequence. Vasopressin terminals of the rat neurohypophysis, which presumably contain enkephalin precursor sequences, exhibited enkephalin-like immunostaining after tryptic cleavage. ACTH/beta-endorphin cells of the rat intermediate pituitary, which synthesize the enkephalin sequence at the N-terminus of Beta-endorphin, exhibited enkephalin=like immunoreactivity when sections were treated with alpha-chymotrypsin or trypsin, but not after incubation with leucine-aminopeptidase or carboxypeptidase-B. Enkephalin-like immunostaining could not be induced in any way in ACTH/beta-endorphin cells of the anterior pituitary. Enzymatic cleavage may give additional information in immunocytochemical localization studies on neuropeptide sequences in secretory nerves and hormonal granules.