INVOLVEMENT OF SERETONIN IN COLD-INDUCED THERMOGENESIS IN MUSCOVY DUCKLINGS: A HPLC STUDY Short communication

On the basis of its marked thermogenic and lipolytic effects in birds, glucagon appears as a strong mediator of avian nonshivering thermogenesis (NST).The present work was performed to test whether glucagon administration acts directly on avian thermoregulatory mechanisms by inducing thermogenesis or indirectly through the participation of serotonin (5-HT); a widely distributed monoamine neurotransmitter within the brain of vertebrates that contributes to the control of neural activity. Our experiments aim at studying the effects of intraperitoneal injection of glucagon on metabolic rates and energy metabolites using cold-acclimated ducklings which developed muscle nonshivering thermogenesis. Our results showed that at ambient temperature (25°C), circulating serotonin was decreased in cold acclimated ducklings (–37%) and thermoneutral ducklings. An intraperitoneal injection of glucagon (360 μg.kg–1) was followed after 10 min by prominent lipolysis and a large increase in circulating serotonin. The increase of serotonin levels was less pronounced in cold acclimated ducklings. According to our results, the thermogenic action of glucagon in birds involves at least the stimulation of serotonin and lipids. We suggest the presence of a potential adaptive mechanism associated with peripheral serotoninergic activity during cold acclimation and leading to nonshivering thermogenesis.