Serum catecholamine and hormonal titers in the hibernating snake Naja haje haje, with reference to the annual climatic cycle

(1)The analysis of catecholamines revealed alterations in norepinephrine levels in the blood serum and the central nervous system of the Egyptian cobra during the different phases of the hibernation cycle. This may reflect an increased central demand for norepinephrine as a mediator for adaptive changes to cold.(2)The low and variable concentration of dopamine suggests retarded synthesis during all the phases studied.(3)Serotonin may be depleted or associated with increased activity of serotonergic neurons during cold acclimation. This increases the rate of turnover of serotonin to 5-hydroxy indole acetic acid.(4)Cricannual measurements of cortisol and adrenocorticotrophic hormones revealed marked suppression that would clarify the direct effect of hibernation on higher centers. The decreased levels during prehibernation and hibernation were restored in normothermic animals when the pituitary-adrenal axis resumed its activity.(5)The decline in thyroid hormone concentrations has its behavioural and physiological responses that lead to seasonal adjustments in the hibernating cobras.