Effects of gold thioglucose on food intake, growth and forebrain histology in goldfish, Carassius auratus

Abstract

The effects of gold thioglucose (GTG) injected intraperitoneally or into the ventricles of the brain on food intake, body weight gain, and forebrain histology in the goldfish were investigated. GTG caused a dose-dependent decrease in food intake, and usually initially caused loss of body weight, or at least slowed the rate of weight gain for up to 4 weeks. Over a long term the tendency was for recovery of normophagia and recovery of the normal rate of body weight gain. No significant effects on plasma glucose concentrations or growth hormone concentrations were detected following GTG treatment. No lesions were observed in the ventromedial hypothalamus of goldfish following intraperitoneal or brain injection of GTG. A dose dependent hypertrophy of the ependyma of the forebrain was found following brain injection of GTG. However, ependymal hypertrophy was found in only about half of the fish injected intraperitoneally with GTG at a dosage causing hypophagia. There was disruption of the ependyma lining the lateral-dorsal aspect of the lateral recess of the third ventricle, and some hypertrophy of the adjacent nucleus recessus lateralis, following brain injection, but not intraperitoneal injection, of a dose of GTG effective in causing decreased weight gain and hypophagia. Since no consistent histological effects of GTG were observed, its site of action in causing decreased weight gain and hypophagia in the goldfish is unknown. Fish injected with gold chloride all died soon after injection. Gold thiomalate injection caused weight loss and slowed the rate of weight gain, similar to GTG. The mechanism by which GTG causes hypophagia and decreased growth in goldfish is probably not related to the specific uptake of glucose by some brain center.