EFFECT OF CHEMICAL SYMPATHECTOMY ON SERUM LEVELS OF THYROID-HORMONES AND THE BIOCHEMICAL PROFILE OF DOMESTIC PIGEONS

Recent studies have stressed the importance of the cholinergic system on avian metabolism. However, the role of the sympathetic nervous syst em (SNS) remains unclear. The present study was, therefore, aimed to p robe the mechanisms for modulation of avian metabolism by the sympathe tic nervous system after inhibition of the adrenergic responses. Activ ities of serum thyroid hormones (tri-iodothyronine, T-3, and thyroxine , T-4), body weight, hepatic weight, as well as total lipid and water content in the liver and body temperature were some of the parameters examined after chemical sympathectomy with 6-hydroxydopamine (6-OHDA) and reserpine treatment in 24-h starved pigeons. In addition, glucose was administered to the pigeons to identify the regulatory role played by glucose after disruption of the SNS. A reduction in body weight of the pigeons and an enhancement in the lipogenic machinery along with a corresponding increase in water content were some of the obvious eff ects in 6-OHDA + reserpine treated, as well as glucose-loaded sympathe ctomized birds. The cloacal temperature (T-c) and both the thyroid hor mones showed a drastic decrease while the T-3/T-4 ratio was augmented as a result of sympathectomy. However, serum T-3 and T-4 levels were r estored to control values when glucose load was given, indicating that glucose might be reversing some of the detrimental effects of 6-OHDA treatment by activating intrinsic autoregulatory mechanisms of thyroid gland, thereby reviving the levels of thyroid hormones. Thus, the inf luence of SNS appears to be crucial in the maintenance of serum thyroi d hormones and body temperature, as well as metabolic activities of he patic cells.