Opiate peptides modulate somatostatin release from dispersed hypothalamic cells

Alpha-melanocyte-stimulating hormone (MSH) and [Nle4,D-Phe7]-alpha-MSH: effects on core temperature in rats

The thermoregulatory effects of alpha-melanocyte stimulating hormone (MSH), its potent analog, [Nle4,D-Phe7]-alpha-MSH (NDP-MSH), and the 1-7, 4-10, and 7-13 amino acid fragments of NDP-MSH were examined by administering these substances to the anterior hypothalamic-preoptic area (AHPOA) of rats. In Experiments 1a (MSH) and 1b (NDP-MSH), animals received 0, 0.5, 1, 5, 10, or 50 pM peptide in 0.5 microliters sterile saline (n = 6/group), with core rectal temperatures being recorded 0, 10, 20, 30, 40, 50, and 60 min after injection. In Experiment 2, subjects received 5 pM NDP-MSH1-7, NDP-MSH4-10, NDP-MSH7-13, NDP-MSH, or the vehicle, 0.5 microliters sterile saline, in a counterbalanced fashion (n = 13). Results indicated a significant effect of dose for both MSH, F(5, 30) = 2.81, p = 0.03, and NDP-MSH, F(5, 30) = 4.98, p = 0.002. A Newman-Keul's analysis indicated that mean temperatures for all groups receiving MSH or NDP-MSH were significantly greater than for the group that received saline (p < 0.05). An analysis of the data from Experiment 2 indicated a significant effect of substance, F(4, 48) = 17.31, p < 0.001. Mean temperature of animals receiving NDP-MSH, the 4-10, or the 7-13 fragments, did not differ from each other but were significantly greater than mean temperatures for animals receiving sterile saline or the 1-7 fragment of NDP-MSH (p < 0.05).

Methods for the study of somatostatin

It is clear from the above that there are a number of methods for study of SRIF release. From the standpoint of convenience, the in vitro static incubation of ME is the most practical technique at the present time. Using this preparation SRIF release has been found to be modified by a number of neurotransmitters and peptides, and studies on the mechanism of release of the peptide have been initiated. There is no doubt that such studies should be complemented by perifusion studies, by studies involving larger pieces of the hypothalamus which encompass the entire somatostatinergic neuron, and by in vivo studies to determine the correlation of in vivo and in vitro release. Among the in vivo techniques which have been utilized, the push-pull cannula technique employing cannulae implanted in hypothalamus or anterior pituitary gland offers the most promise. A summary of the effects of some neurotransmitters and neuropeptides on hypothalamic SRIF secretion is reported in Table. I.

Opiate inhibition of growth hormone secretion in young chickens

Plasma concentrations of growth hormone (GH) were decreased following the intravenous administration of morphine sulfate. Maximum inhibition of GH secretion was observed 40 min after morphine sulfate challenge. At this time, doses of morphine sulfate (at 5 mg and 50 mg/kg) reduced the GH concentrations by 86 and 90%, respectively, in comparison with those in the vehicle-injected controls. An opiate antagonist, naloxone, had no stimulatory effect on basal GH concentrations, but attenuated the GH response to morphine. Neither morphine nor naloxone had any significant effect on circulating luteinizing hormone (LH) levels. These results indicate an inhibitory opiate pathway in the control of GH release and demonstrate effects on GH and LH secretion contrary to those observed in mammalian species.

Central nervous system effects of peptides, 1980-1985: a cross-listing of peptides and their central actions from the first six years of the journal Peptides

A tabular synopsis is presented for articles concerned with the effects of peptides on the central nervous system that appeared in the journal Peptides from 1980-1985. A table arranged alphabetically by peptide and one arranged by effects, both listing routes of injection, species, direction of change, and qualifying notes, provides easy cross-referencing of peptides and their effects. Over 80 peptides and over 135 effects are listed. The list of peptides includes, but is not limited to: ACTH, angiotensin, bombesin, bradykinin, calcitonin, casomorphin, CCK, ceruletide, CGRP, CRF, dermorphin, DSIP, dynorphin, endorphins, enkephalins, GRF, gastrin, LHRH, litorin, metkephamid, MIF-l, motilin, MSH, NPY, NT, oxytocin, ranatensin, sauvagine, substances P and K, somatostatin, TRH, VIP, vasopressin, and vasotocin. The list of effects includes, but is not limited to: aggression, alcohol, analgesia, attention, avoidance, behavior, cardiovascular regulation, catalepsy, conditioned behavior, convulsions, dopamine binding and metabolism, discrimination, drinking, EEG, exploration, feeding, fever, gastric secretion, GI motility, grooming, learning, locomotor behavior, mating, memory, neuronal activity, open field, operant behavior, rearing, respiration, satiety, scratching, seizure, sleep, stereotypy, temperature, thermoregulation and tolerance.

Thyrotropin-releasing hormone levels decrease in hypothalamus of aging rats

Because hypothalamic and extrahypothalamic levels of thyrotropin-releasing hormone immunoreactivity (TRH-IR) undergo profound changes during the prenatal and early postnatal period in rats, similar effects with advanced aging were anticipated. For this reason we measured hypothalamic and reproductive tissue levels of TRH-IR, hypothalamic levels of somatostatin (SRIF), and beta-endorphin (EP), serum levels of prolactin (Prl), growth hormone (GH), thyrotropin (TSH), and thyroxine (T4) in young, sexually mature and 24-28 month-old male Long-Evans and Sprague-Dawley rats. Hypothalamic and prostatic levels of TRH-IR were consistently reduced as were the levels of T4 in old rats compared to young controls. Aging did not change the ratio of TRH to the major TRH-like peptide in prostates, as determined by high pressure liquid chromatography (HPLC) or the levels of hypothalamic SRIF and EP. All of the hypothalamic TRH-IR in both old and young male rats consisted of TRH by HPLC. Falling hypothalamic TRH levels and TRH secretory capacity may play a role in the blunted TSH response to cold stress in old rats.

Low levels of somatostatin in human CSF mark depressive episodes

Somatostatin-like immunoreactivity was measured in the cerebrospinal fluid (CSF) of 85 inpatients with current or recent episodes of major depressive disorders, diagnosed according to Research Diagnostic Criteria (RDC) as assessed with the Schedule for Affective Disorders and Schizophrenia (SADS). Several biopsychiatric tests were run during the same week of investigation. Results indicate low levels of CSF somatostatin to be a state marker for episodes of depression characterized by sad appearance, feelings of tiredness, insomnia, and subjective inability to acknowledge any external precipitants for the depression. CSF somatostatin was negatively related to platelet monoamine oxidase (MAO) activity; MAO activity appeared to account better for the degree of melancholic features than did somatostatin. The ratio between 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA) in CSF also correlated negatively with somatostatin. A positive relationship was noted between CSF xanthine and somatostatin. There was a highly significant curvilinear correlation between CSF somatostatin and serum TSH concentrations, but no correlations between CSF somatostatin and serum GH or prolactin, or with plasma cortisol before or after dexamethasone.

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.