Which Opioid Receptor Mechanism Modulates Feeding?

There is substantial evidence for the role of endogenous opioid peptides in the regulation of appetite. This communication examines the possible opioid peptide mechanism(s) which are involved in appetite regulation. In the rat, activation of both the dynorphin-kappa opioid receptor and the beta-endorphin-epsilon opioid receptor appear to enhance feeding, most probably acting in different areas of the central nervous system. It also appears that rats may have a mu anorectic system. Too few studies have been undertaken to define whether the delta or sigma receptor systems are also involved in feeding responses. It is becoming apparent that a great deal of species diversity exists in the feeding responses to opiates, making it difficult to extrapolate the results obtained in rats to other species. In humans, studies with naloxone suggest an opioid sensitive feeding system which possibly is specifically involved in the regulation of carbohydrate uptake. In addition, we report here preliminary data suggesting the presence of a mu anorectic system in humans. Thus, analogous to the findings for the role of opioid receptors in analgesia, it appears that multiple opioid receptors may be involved in appetite regulation, each receptor relating to a different aspect of feeding.     

Abnormal zinc metabolism in type II diabetes mellitus

Zinc metabolism in 20 patients with stable type II diabetes mellitus was investigated. Twenty-five percent of these patients had depressed serum zinc concentrations, and all demonstrated hyperzincurla. Urinary zinc loss was greater when proteinuria was present and correlated with the mean serum glucose concentration. Studies of gastrointestinal zinc absorption suggested zinc malabsorption in patients with type II diabetes mellitus. Glucose infusion in normal dogs produced hyperzincuria without a diminution in serum zinc. It is concluded that hyperzincuria, resulting from a glucose-mediated process that is not osmotic, interacts with impaired zinc absorption to produce zinc deficiency in patients with type II diabetes mellitus.     

Effect of renal transplantation on pituitary gonadal function.

Twelve adult male patients who had undergone successful renal transplantation were investigated. The gonadotropin responses to 100 microgram luteinizing hormone-releasing hormone (LRH) were studied, and basal serum testosterone and prolactin assayed. Significantly elevated mean basal levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were found, associated with a correspondingly excessive LH and FSH response to LRH. Mean basal serum testosterone levels in the posttransplant patients were significantly lower than in normal controls, while the mean basal prolactin levels were similar in the two groups. The results were not influenced by the varying degrees of renal function found in the posttransplant patients.     

Temporal artery pulse amplitude wave shapes in migraineurs: A methodological investigation

This paper describes three atypical wave forms observed in temporal artery pulse amplitude recordings. Analysis of concurrent EMG records showed that two of these wave forms, spikes and spasms, were associated with muscle changes and may be regarded as artefacts. The third wave form, double peak, was not associated with EMG changes and may represent a local vascular dysfunction. Double peaks were observed to occur more frequently in migraineurs and specifically at the site of pain onset. Explanations for double peaks are discussed. It is concluded that they indicate a dysfunction in the regulation of vascular tonicity. This dysfunction is described as variable tonicity.     

The endocrinology of the opiates and opioid peptides

Since the isolation of the enkephalins five yr ago, there has been an explosive increase in knowledge concerning the effects of the opiates and opioid peptides. This review deals with the interactions of opiates with the endocrine system in rat and man. The opioid peptides have been demonstrated to exert a variety of effects on pituitary hormone secretion in rat and man. In the rat, opiates stimulate growth hormone, prolactin and ACTH release and inhibit the release of the glycoprotein hormones. In man, the physiologic role of the endogenous opiates appears to be involved predominantly in ACTH and gonadotrophin regulation. Opiate effects are mainly exerted at the level of the hypothalamus but further modulating effects may occur at the pituitary and at end-organs. Opiate-induced hormonal effects appear to be mediated through dopaminergic and/or serotonergic mechanisms. Recent studies have also suggested a possible local neuromodulatory role for the opioid peptides in the control of carbohydrate metabolism and reproductive processes.