Role of neural input in photoperiod-induced changes in hamster brown adipose tissue

Repeated injections of 6-hydroxydopamine in Syrian hamster neonates maintained under long-day (16L:8D) photoperiod for 30 days retarded body growth and cellular proliferation in brown adipose tissue but did not affect the cellular content of mitochondrial proteins. Sympathectomy reduced GDP binding to isolated mitochondria without affecting the organelle uncoupling protein (UCP) content. Unilateral surgical denervation of the brown fat pad of 30-day-old hamsters caused loss of tissue protein and succinate dehydrogenase as well as reductions in GDP binding and UCP content of isolated mitochondria but did not prevent an increase in GDP binding observed after 1 month exposure to a short-day photoperiod. The increased GDP binding was not due to increased UCP content. These results indicate that an adrenergic neural input may not be essential for UCP expression in Syrian hamsters and that changes in GDP binding observed in a short-day photoperiod environment can be observed in denervated tissue in the absence of changes in mitochondrial UCP content.