Elizabeth C. Lotter

Peptides and the control of meal size

SummaryThere are now a large number of experiments demonstrating that peripheral administration of exogenous cholecystokinin or its synthetic analogue, CCK-8, reduces meal size in a number of species. The peptide interacts with other factors which influence satiety, and treatments thought to be effective in eliciting secretion of cholecystokinin have predictable effects on meal size. Cholecystokinin is effective in the genetically obese Zucker rat, obese rats with lesions of the ventromedial hypothalamus, and subdiaphragmatically vagotomized rats. Somatostatin and bombesin are also reasonable candidates for satiety factors. Intraperitoneal naloxone reduces meal size in rats, and beta-endorphin injected intraventricularly causes an increase in meal size of 50% over 30 minutes. We conclude that cholecystokinin and bombesin may interact in weight regulation and control of meal time food intake.

Injections of insulin and changes of body weight

Abstract The effects of injections of long acting protamine zinc insulin (PZI) on body weight were studied on rats. Route of administration and dilution of PZI were parametrically varied. Results indicate that subcutaneous injections are more effective than intraperitoneal injections, and that concentrated insulin is more effective than dilute. Since insulin injections result in hypoglycemia and hyperphagia, a further series of experiments examining plasma glucose levels under various experimental conditions is reported. Intraperitoneal injections caused a more rapid decrease of glucose, and one which was quickly reversed, relative to subcutaneous injections. The results are discussed in terms of these changes of glucose.

Effect of force-feeding upon basal insulin levels of rats.

Summary Rats were over- or under-fed to achieve a wide range of body weights. The effect of this treatment on basal insulin levels, with and without pretreatment with atropine, was examined. Basal insulin was positively correlated with body weight and this relationship was essentially unchanged in the presence of atropine.

Cholecystokinin-induced satiety in weanling rats

Abstract Intraperitoneal injections fo the synthetic C-terminal octapeptide of cholecystokinin (CCK) into fasted 21-day-old weanling rats produced a significant suppression of intake of solid and liquid diets. Similar injections had no effect on water consumption of thirsty weanlings. The early appearance of CCK-induced satiety is consistent with the idea that this mechanism is responsible for the effectiveness of gastrointestinal factors in determining intake of very young rats.

Neuroendocrine regulation of food intake and body weight

Abstract This paper reviews the effects of peptide hormones upon food intake. These effects are seen as falling into one of two categories depending upon whether the hormone in question is affected by the degree of adiposity. Many gut peptides, such as CCK and somatostatin, influence the size of individual meals and presumably reflect only the calories involved with that meal. Other peptides, especially insulin as it acts at the CNS, influence the size of all meals by indicating the current degree of adiposity. Such signals reflect not only single meal calories but also calories stored in the adipose beds and are therefore often called “long-term” signals.

Intraventricular Angiotensin Elicits Drinking in the Baboon

Summary Cannulas aimed at the lateral cerebral ventricles were surgically implanted in baboons. A-II (5 /xg/animal) or control injections were made on subsequent days and water intake recorded to determine the patency of the cannulas. We found that (a) baboons drink considerable water after the IVT administration of A-II, (b) the response diminishes but still persists with repeated A-II tests spread over a several-month interval, and (c) elevated drinking in response to the administration of A-II is a practical way to confirm the success of ventricular cannulation.

Appetite suppression caused by CCK is diet specific in VMH-lesioned rats

Intraperitoneal injections of the C-terminal octapeptide of cholecystokinin-pancreozymin (CCK) failed to inhibit 5.5-h-fasted feeding of a high-fat diet in rats with electrolytic lesions of the ventromedial hypothalamus. Similar injections significantly reduced the intake of a high-fat diet in sham-lesioned controls. These results are consistent with Powley’s (1977) cephalic phase hypothesis (CPH) and are interpreted to mean that rats with electrolytic lesions of the ventromedial hypothalamus, when given a highly palatable diet, demonstrate a prolonged cephalic reflex, which results in metabolic disturbances which may override the effect of CCK at the 40 U/kg dose.

A dual-purpose device for protecting brain implants of baboons.

A device is described which is relatively easy to construct and which can be used to protect brain implants affixed to the skull of large primates. The device is essentially a stainless steel ring cemented around the brain implant. A plexiglass dome can then be attached to the ring to protect the implant. Further, a second device can be constructed which attaches to the ring and which provides gentle leverage to the brain implant to remove adhered obturators.