Brain Neuropeptide Research Articles

S6 phosphorylation results from prothoracicotropic hormone stimulation of insect prothoracic glands: a role for S6 kinase.

The insect prothoracic glands are the source of steroidal molting hormone precursors and the glands are stimulated by a brain neuropeptide, prothoracicotropic hormone (PTTH). Previous work from this laboratory revealed that PTTH acts via a cascade including Ca2+/calmodulin activation of adenylate cyclase, protein kinase A, and the subsequent phosphorylation of a 34 kDa protein (p34) hypothesized, but not proven, to be the S6 protein of the 40S ribosomal subunit. The immunosuppressive macrolide, rapamycin, is a potent inhibitor of cell proliferation, a signal transduction blocker, and also prevents ribosomal S6 phosphorylation in mammalian systems. We demonstrate here that rapamycin inhibited PTTH-stimulated ecdysteroidogenesis in vitro by the prothoracic glands of the tobacco hornworm, Manduca sexta, with half-maximal inhibition at a concentration of about 5 nM. At concentrations above 5 nM, there was a 75% inhibition of ecdysteroid biosynthesis. Similar results were observed with the calcium ionophore (A23187), a known stimulator of ecdysteroidogenesis. Most importantly, the inhibition of ecdysteroid biosynthesis was accompanied by the specific inhibition of the phosphorylation of p34, indicating that p34 indeed is ribosomal protein S6. In vivo assays revealed that injection of rapamycin into day 6 fifth instar larvae resulted in a decreased hemolymph ecdysteroid titer and a dose-dependent delay in molting and metamorphosis. When S6 kinase (S6K) activity was examined using rapamycin-treated prothoracic glands as the enzyme source and a synthetic peptide (S6-21) or a 40S ribosomal subunit fraction from Manduca tissues as substrate, the date revealed that rapamycin inhibited S6K activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermoregulatory effect of intracerebral injections of neuropeptide Y in rats at different environmental temperatures

1. 1. In order to characterize the thermoregulatory actions of brain neuropeptide Y (NPY), the effects of intra-third ventricular (I3V) injection of NPY on temperatures of colon ( T co), brown adipose tissue ( T BAT) and tail skin ( T s) were observed at ambient temperatures ( T a) of 19 and 8°C. 2. 2. The injection of NPY in a dose of 8 mcg/100 g body wt evoked a fall of T co by about 2°C in both neutral and cold environments. NPY (4 and 8 mcg/100 g body wt) induced dose-dependent T co falls in rats at thermoneutral environment. The thermolytic reactions induced by I3V administration of NPY were associated with a fall in T BAT but no changes in I s were observed. 3. 3. The results suggest that NPY may mediate hypothermic response in neutral and cold environments mainly by its effects on the brown adipose tissues in the rat.

Age-related changes in the contents of neuropeptides in the rat brain and pituitary

β-Endorphin, Leu-enkephalin, Met-enkephalin, substance P, somatostatin, and cholecystokinin were measured in the brain and the pituitary of male Sprague-Dawley rats aged 3 months, 12 months, and 22 months. β-Endorphin, Met-enkephalin and Leu-enkephalin contents in the neurointermediate lobe, and the enkephalin levels in the anterior lobe of the pituitary increased with age. The increases in contents were both in the day and at night for β-endorphin and Met-enkephalin. However, the increase for Leu-enkephalin content was in the day only. Hypothalamic β-endorphin content decreased with age only in the day. β-Endorphin and Leu-enkephalin contents in the brain stem, and Leu-enkephalin levels contents in the cortex decreased with age at night. Leu-enkephalin in the striatum decreased with age in the day. There was also an age-related decrease for somatostatin and substance P contents in the striatum and the hypothalamus in the day, and in cholecystokinin levels in the hippocampus, and the hypothalamus at night. It is concluded that there are age differences in neuropeptide levels, and that these changes may differ according to diurnal rhythms.

Participation of endogenous neuropeptide Y in the suppression of baroreceptor reflex response by locus coeruleus in the rat

We evaluated the potential participation of endogenous brain neuropeptide Y (NPY) in the suppression of baroreceptor reflex (BRR) response by locus coeruleus (LC), using adult male Sprague-Dawley rats anesthetized with pentobarbital sodium (40 mg/kg, i.p.). Bilateral microinjection of an antiserum against NPY (1:20, 20 nl) into the caudal one-third level of the nucleus tractus solitarii (NTS), the terminal site for baroreceptor afferent fibers, significantly reversed the suppressive effect of electrical or chemical activation of the LC on the BRR response. Treatments with NPY (4.65 pmol, 20 nl), normal rabbit serum, aCSF and heat-inactivated NPY or NPY antiserum, on the other hand, were ineffective. The LC-promoted inhibition of the BRR response was also attenuated by the α 1- adrenoceptor antagonist prazosin (50 pmol, 20 nl), either microinjected alone or in combination with NPY antiserum into the bilateral NTS. Mathematical treatment of our data revealed that the depressive effect on the BRR response of NPY or NE released at the NTS following LC activation manifested different time-course and magnitude. The one by endogenous NPY maximized at 40 min and amounted to no more than 20% of, whereas that by NE peaked at 10 min and contributed no less than 30% to, the suppression. These results suggest that both endogenous NPY and NE may participate in the suppression of BRR response by the LC at the NTS.

Insect myotropic peptides: differential distribution of locustatachykinin- and leucokinin-like immunoreactive neurons in the locust brain

Locustatachykinin I is one of four closely related myotropic neuropeptides isolated from brain and corpora-cardiaca complexes of the locust Locusta migratoria. Antiserum was raised against locustatachykinin I for use in immunocytochemistry. It was found that the antiserum recognizes also locustatachykinin II and hence probably also the other two locustatachykinins due to their similarities in primary structure. Locustatachykinin-like immunoreactive (LomTK-LI) neurons were mapped in the brain of the locust, L. migratoria. A total of approximately 800 LomTK-LI neurons were found with cell bodies distributed in the proto-, deuto- and tritocerebrum, in the optic lobes and in the frontal ganglion. Processes of these neurons innervate most of the synaptic neuropils of the brain and optic lobes, as well as the frontal ganglion and hypocerebral ganglion. The widespread distribution of LomTK-LI neurons in the locust brain indicates an important role of the locustatachykinins in signal transfer or regulation thereof. As a comparison neurons were mapped with an antiserum against the cockroach myotropic peptide leucokinin I. This antiserum, which probably recognizes the native peptide locustakinin, labels a population of about 140 neurons distinct from the LomTK-LI neurons (no colocalized immunoreactivity). These neurons have cell bodies that are distributed in the proto- and tritocerebrum and in the optic lobe. The processes of the leucokinin-like immunoreactive (LK-LI) neurons do not invade as large areas in neuropil as the LomTK-LI neurons do and some neuropils, e.g. the mushroom bodies, totally lack innervation by LK-LI fibers. In some regions, however, the processes of the LomTK-LI and LK-LI neurons are superimposed: most notably in the central body and optic lobes. A functional relation between the two types of neuropeptide in the locust brain can, however, not be inferred from the present findings.

Norepinephrine levels in paraventricular nucleus of spontaneously hypertensive rats: role of neuropeptide Y

Recent evidence supports the view that the sympathetic system actively participates in the development of hypertension. Because norepinephrine, contained within central neurons involved in cardiovascular sympathetic regulation, is known to coexist with neuropeptide Y, it is possible that a functional interaction between neuropeptide Y and norepinephrine exists within the brain. In an effort to clarify whether or not central catecholamine systems are modulated by neuropeptide Y in hypertensive situations, the paraventricular nucleus of spontaneously hypertensive rats was exposed to neuropeptide Y (10(-9) M), and levels of norepinephrine were sampled by microdialysis. Norepinephrine levels in spontaneously hypertensive rats were significantly increased and did not change after exposure to neuropeptide Y, in sharp contrast to the decreases seen in Wistar-Kyoto controls. To ascertain whether these alterations in norepinephrine control were specific to the model used, a similar series of experiments was carried out in the paraventricular nucleus of aortic-banded rats. These studies supported the previous findings. Norepinephrine levels in aortic-banded rats were markedly elevated when compared with sham-operated controls and demonstrated no change after exposure to neuropeptide Y, whereas decreases of > 50% were seen in sham-operated controls. These results support the view that mechanisms normally involving neuropeptide Y as a neuromodulator in the paraventricular nucleus are altered in hypertensive situations. It is suggested that hypertension may precipitate changes in mechanisms involving brain neuropeptide Y and increased sympathetic activity.

Neuropeptides in the insect brain: a review.

Neuropeptides in the insect brain: a review.

Neuropepride Regulators of Insect Corpora Allata

SYNOPSIS. Neuropeptides of the insect brain that regulate juvenile hormone synthesis by the corpora allata include allatotropins, stimulatory modulators, and allatostatins, inhibitory modulators. A radiochemical assay for juvenile hormone synthesis by corpora allata in vitro was utilized in the high pressure liquid chromatographic isolation of brain neuropeptides leading to the determination of their primary structure. Identified are an allatotropin and an allatostatin from a Lepidopteran, Manduca sexta , and a family of five allatostatins from a Dictyopteran, Diploptera punctata . These neuropeptides are all unique, effective at low concentration (10−10 to 10−8 M), act quickly (within hrs) and appear to be effective only within the same order of insects as that from which the peptides were isolated. The physiological state of the corpora allata conditions the effectiveness of the allatostatins of D. punctata . These neuropeptide regulators of corpora allatal function may have multiple regulatory roles. This is indicated for D. punctata allatostatin I by specific receptors in brain and fat body as well as in corpora allatal membrane preparations, and also by immunocytochemical localization of allatostatin I in medial nerve cells that terminate within the brain as well as in the lateral neurosecretory cells that terminate on corpus allatum cells.

C-type natriuretic peptides are potent dilators of shark vascular smooth muscle.

Previous studies of the effects of C-type natriuretic peptides (CNP) in intact mammals have demonstrated limited hypotensive responses, in contrast to other natriuretic peptides. Our previous studies, on isolated vascular smooth muscle (VSM) from various fish species, utilizing either mammalian or non-homologous fish atrial natriuretic peptides (ANP), have demonstrated vasodilation with a relatively high sensitivity (EC50 approximately 5 nM). The recent sequencing of a C-type natriuretic peptide from the heart of the dogfish shark, Squalus acanthias, has enabled us to compare the efficacy of this peptide on aortic VSM from that species with two other CNPs (from killifish and pig), as well as rat ANP. The EC50 of dilation for sCNP, as well as kCNP and pCNP, was 0.5 nM, over 15 times lower than the EC50 of the response to rANP. These data suggest that CNP is released from the dogfish shark heart and is a circulating hormone with potent vasodilatory effects, in sharp contrast to the apparent role of CNP predominantly as a brain neuropeptide in mammals.

Effect of allatostatin and proctolin on antennal pulsatile organ and hindgut muscle in the cockroach, Diploptera punctata

Diploptera punctata allatostatins are brain neuropeptides that inhibit juvenile hormone synthesis by corpora allata. They also occur in nerves of many organs other than corpora allata. The distribution of allatostatins in, and the effect of allatostatins on two other organs, antennal pulsatile organ and hindgut, are demonstrated here. Allatostatin I-like immunoreactive material is present in cells of subesophageal and terminal abdominal ganglia; these ganglia are known to contain the cells that project to antennal heart nerve and proctodeal nerve, respectively. Electron micrographs of both organs show nerve terminals with allatostatic immunoreactive granules along with terminals containing nonimmunoreactive granules. Immunoreactive neurosecretory granules are about 200 nm in largest dimension. In the antennal pulsatile organ, profiles of the nerve terminals are larger in the ampullar wall than in the muscle; in hindgut the terminals with immunoreactive granules are associated with the muscle net below the circular muscle. Hindgut responded to allatostatins I and IV with a dose-dependent decrease in amplitude and frequency of contraction that was reversible, with the threshold concentration for response between 10(-8) and 10(-7) M. In contrast, pulsatile organ muscle showed no such change with either allatostatin at 10(-7)-10(-4) M. However, both organs responded to proctolin with increased amplitude and frequency of contractions. Allatostatins I and IV inhibited the proctolin-induced increase of hindgut contraction, whereas no such effect was seen in antennal pulsatile organ muscle. Extract of antennal pulsatile organ muscle showed proctolin-like bioactivity that comigrated with authentic proctolin on three sequential HPLC systems.

Tonic suppression of baroreceptor reflex response by endogenous neuropeptide Y at the nucleus tractus solitarius of the rat

We evaluated the potential participation of endogenous brain neuropeptide Y (NPY) in central cardiovascular regulation, using adult male Sprague-Dawley rats anesthetized with pentobarbital sodium (40 mg/kg, i.p.). Bilateral microinjection of NPY (4.65 pmol) into the caudal one-third level of the nucleus tractus solitarius (NTS), the terminal site for baroreceptor afferent fibers, promoted a significant suppression of the baroreceptor reflex (BRR) response. The maximal inhibition occurred at 30–40 min postinjection, and amounted to −42.7 ± 8.6% (mean ± S.E.M., n = 9). The same treatment, however, only caused transient (≈5 min) hypotension and bradycardia. Blocking the endogenous NPY activity at the NTS with its antiserum appreciably enhanced the sensitivity of BRR response (+ 59.2 ± 18.8%, mean ± S.E.M., n = 6), but had no appreciable effect on systemic arterial pressure or heart rate. These results suggest that neurons that contain NPY may participate in central cardiovascular regulation by tonically suppressing the BRR response, possibly by exerting an influence on the baroreceptive neurons at the NTS.

Brain neuropeptides: Changes by treatment with the convulsants pentylenetetrazole and bicuculline

1. The effects of chemically induced convulsions, clinically similar to those elicited by electroconvulsive treatment (ECT), on brain regional distribution of neuropeptide Y-, neurokinin A-, substance P- and neurotensin-like immunoreactivities were studied in the rat 2. Pentylenetetrazole (PTZ) and bicuculline (BIC) were used to induce grand mal seizures. Rats were divided into three groups receiving one of the following treatments: Saline, PTZ (45 mg/kg) or BIC (1.5 mg/kg). 3. After sacrifice by focused microwave irradiation, brains were dissected, peptides extracted and measured by specific radioimmunoassays. 4. Repeated grand mal convulsions induced by PTZ, in similarity to ECT, markedly increased NPY-LI concentrations in frontal cortex and hippocampus. In contrast to ECT, no changes in NKA- or SP-LI levels were seen. NT-LI was lowered in striatum. 5. Bicuculline effects were more circumscribed: some animals developed grand mal and died while convulsing (peptides not measured), others did not develop generalized seizures and were sacrificed after the fourth treatment 6. The results demonstrate a similar effect of PTZ and ECT on regional NPY-LI concentrations and raise the possibility that grand mal, regardless of etiology, is necessary for effects on peptides.

Neuropeptides in rat brain: modification by lithium and electroconvulsive treatment

Neuropeptides in rat brain: modification by lithium and electroconvulsive treatment

Distribution of preproatrial natriuretic peptide mRNA in rat brain detected by in situ hybridization of DNA oligonucleotides: enrichment in hypothalamic and limbic regions.

The expression and distribution of mRNA encoding preproatrial natriuretic peptide (ppANP) in rat brain has been investigated by in situ hybridization of two 35S-labeled synthetic DNA oligonucleotides, based on a cDNA clone sequence that encodes rat ppANP. The highest relative concentrations of ppANP mRNA were detected in the medial preoptic hypothalamic nucleus ("anteroventral/third ventricle region") and the medial habenula. Moderate concentrations of ppANP mRNA were observed in the CA1 pyramidal cells of the hippocampus, the endopiriform nucleus, the arcuate nucleus, the zona incerta, and cells of the pontine tegmental and peduculopontine nuclei. Several of these regions, including the habenula and the hypothalamic areas, have previously been reported to contain atrial natriuretic peptide (ANP)-like immunoreactivity, but the expression of ppANP mRNA in CA1 pyramidal cells suggests the occurrence of differential translation of ppANP mRNA into protein product in different brain regions, or the existence of different immunological forms of the peptide. The abundance of ppANP mRNA in brain was relatively low in comparison with that previously reported for many other mRNA species encoding other brain neuropeptides. These results demonstrate that ANP gene expression occurs in discrete neuronal populations of the CNS and that studies of the regulation of this expression should now be possible using quantitative in situ hybridization.

Changes in neuropeptide Y after experimental traumatic brain injury in the rat.

We utilized a model of fluid percussion (FP) brain injury in the rat to examine the hypothesis that alterations in brain neuropeptide Y (NPY) concentrations occur following brain injury. Male rats (n = 44) were subjected to FP traumatic brain injury. One group of animals (n = 38) was killed at 1 min, 15 min, 1 h, or 24 h after brain injury, and regional brain homogenates were analyzed for NPY concentrations using radioimmunoassay. A second group of animals (n = 6) was killed for NPY immunocytochemistry. Concentrations of NPY in the injured left parietal cortex were significantly elevated at 15 min post injury (p less than 0.05). No changes were observed in other brain regions. NPY-immunoreactive fibers were seen at 15 min post injury predominantly in the injured cortex and adjacent hippocampus. These temporal changes in NPY immunoreactivity, together with previous observations concerning posttraumatic changes in regional CBF in these same areas, suggest that an increase in region NPY concentrations after brain injury may be involved in part in the pathogenesis of posttraumatic hypoperfusion.

Anatomical organization of the hypophysiotrophic systems in the electric fish, Apteronotus leptorhynchus.

The organization of afferents to the pituitary was investigated by applying DiI crystals to the pituitary or pituitary stalk of the gymnotiform electric fish, Apteronotus leptorhynchus. Most hypophysiotrophic cells were found in the hypothalamus and were distributed throughout its rostrocaudal extent: nucleus preopticus periventricularis, pars anterior and posterior; suprachiasmatic nucleus; anterior, dorsal, ventral, lateral, and caudal hypothalamic nuclei; and nucleus tuberis lateralis, pars anterior and posterior. In addition a small number of retrogradely labeled cells were found in the ventral telencephalon (area ventralis, pars ventralis) and, most surprisingly, in a thalamic nucleus (nucleus centralis posterioris). The nucleus preopticus periventricularis pars posterior and the anterior hypothalamic nucleus appear to correspond to the parvicellular and magnocellular divisions of the nucleus preopticus of other teleosts. Integration of these results with immunohistochemical localization of monoamines and neuropeptides in the apteronotid brain suggests many homologies between the hypophysiotrophic nuclei of teleosts and other vertebrates, including mammals. Apteronotus communicates electrically during agonistic and sexual interactions. There are numerous anatomical links between the hypophysiotrophic systems and the brain areas related to electrocommunication.

Beta-endorphin, vasoactive intestinal peptide and cholecystokinin in peripheral blood mononuclear cells from healthy subjects and from drug-free and haloperidol-treated schizophrenic patients.

Beta-endorphin, cholecystokinin and vasoactive intestinal peptide were measured in peripheral blood mononuclear cells of healthy controls, and schizophrenic patients at the first diagnosis before any treatment and after 2 or 15 d of treatment with haloperidol. Beta-endorphin concentrations were similar in controls and untreated patients, and increased with treatment. Cholecystokinin concentrations were higher in patients than in controls, and decreased during treatment. Vasoactive intestinal peptide was lower in patients and did not change with treatment. These observations are consistent with measurements of the same peptides in autopsy samples or cerebrospinal fluid. Peripheral blood mononuclear cells might be an useful tool for the study of some neuropeptides in brain.

Stimulation of sex pheromone production by proteinaceous extracts of the bursa copulatrix in the redbanded leafroller moth

AbstractPheromone biosynthesis in the redbanded leafroller moth, Argyrotaenia velutinana, was stimulated by homogenates of the bursa copulatrix. Although pheromonotropic activity was also extractable from the ovary, the activity of pheromone biosynthesis activating neuropeptide (PBAN) or bursa extracts was not impaired in isolated abdomens by removal of the ovary. Response to the bursa extracts was dependent on the dose administered and the time of incubation. Amounts of pheromone present in adult females of different ages appeared to be correlated with the extractable amount of pheromonotropic activity from their bursa copulatrix. Decapitation did not result in the suppression of burse factor production. Homogenates of the bursa elicited similar effects in both isolated gland and isolated abdomen incubations, but the brain neuropeptide, PBAN, was less active in the former than in the latter. Bursa extracts stimulated pheromone production in isolated abdomen incubations deprived of the bursa copulatrix, but PBAN did not. Loss of activity of bursa homogenates after treatment with either pronase E or carboxypeptidase Y indicated that the pheromonotropic factor is a proteinaceous substance. The mechanism through which pheromone production is regulated in redbanded leafroller moths is discussed. © 1992 Wiley‐Liss, Inc.

Neuropeptides in the Amphibian Brain

Publisher Summary This chapter focuses on neuropeptides in the amphibian brain emphasizing neuroendocrine relations. Neuropeptides are synthesized as multiple molecular variants, and they may play different roles in various organisms. An analysis of the distribution of neuropeptides in vertebrates and their phenotypic plasticity, especially during development, leads to an understanding of the basic neurochemical organization but, at the same time, gives an appreciation of the wide diversity among species. The neuroendocrine and immunological functions exerted by neuropeptides constitute a fundamental link with other homeostatic systems that permit adaptation to a changing environment. Gonadotropin-releasing hormone (GnRH) is a decapeptide amide originally identified in the brain of a pig for its ability to stimulate the release of gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) from the anterior pituitary. The main groups of GnRH-secreting perikarya are located within the telencephalon from the olfactory bulb to the septum. The distribution of GnRH cell bodies and fibers corresponds to the course of the olfactory nervus terminalis, which is a small cranial nerve made of fibers and associated cells that form glanglion-like clusters. In addition, GnRH stimulates the synthesis and release of gonadotropins from the amphibian pituitary. Mammalian GnRH—added in vitro to interrenal gland from male and female Rana esculenta —induces a significant increase in prostaglandin F 2 concentrations.

Modulation of sympathetic activity by brain neuropeptide Y in cardiac hypertrophy

Several observations now support the view that the sympathetic system actively participates in the development of cardiac hypertrophy. Since norepinephrine (NE)-containing neurons involved in cardiovascular regulation in the brain are known to coexist with neuropeptide Y (NPY), it is possible that a functional interaction between NPY and NE exists centrally. In an effort to clarify whether or not central catecholamine systems are modulated by NPY soon after imposing an increased pressure overload on the heart, male Sprague-Dawley rats underwent aortic constriction and were examined 14 days later. Rats were anesthetized and subjected to microdialysis sampling by stereotaxically implanting a probe into the caudal ventrolateral medulla (A 1). Perfusate was collected after a 1-hour stabilization period, purified, and analyzed for interstitial concentrations of NE and other catecholamines using high-performance liquid chromatography with an electrochemical detector. Extracellular NE concentrations in the A 1 area were found to be decreased. These results were associated with increased rate of change in the specific activity of NE (NE turnover) in heart, indicating increased sympathetic activity and an increased left ventricular weight. Also, infusion of NPY (10 −9 mol/L) by microdialysis in the A 1 area resulted in the reduction of NE concentration; epinephrine and dopamine levels were also decreased. In contrast, methionine-enkephalin, another neuropeptide, had no effect on the extracellular catecholamine concentrations in the A 1 area. Since neurons of the A 1 group project almost exclusively to forebrain structures inhibiting sympathetic activity, it is concluded that decreases of NE and other catecholamines in afferent pathways regulating the caudal ventrolateral medulla may lead to an enhanced sympathetic activity. It is suggested that cardiac hypertrophy may be precipitated secondary to changes in brain NPY levels.