Seasonal Features of the Effects of Blockade of Opioid Receptors on Adaptive Behavior in Hibernating Animals

Abstract

Studies of hibernating Yakutianian long-tailed ground squirrels (n = 42) addressed the effects of blockade of opioid receptors with naloxone on behavior in an open field and a holeboard chamber in the autumn (during preparation for hibernation) and in the spring (on waking at the end of hibernation). The inhibitory effects of opioid receptor blockade on systematic parameters of the overall level of CNS activation of the squirrel CNS were more marked in the autumn than in the spring. Biochemical analysis of monoamine contents revealed differences in the noradrenaline/serotonin ratio in the animals’ brains in spring and autumn. It is suggested that the interaction between the opioid and monoaminergic systems, working with a number of other factors, transfers homeostasis in hibernating animals to the new levels required both for preparation for entering hibernation – in autumn – and for transfer to the active homeothermic state – in spring.