Behavioural and spectrum power effects of opioid peptides in chicks

The effects of intracerebroventricular administration of beta-endorphin, dermorphin, D-ala2-methionine-enkephalinamide (DALA) and pentazocine, on behaviour, electrocortical activity and ECoG spectrum power in young chicks were studied. Beta-endorphin, dermorphin and DALA produced dose-dependent behavioural sedation and sleep accompanied by electrocortical high voltage slow wave activity and increase in total voltage power with a predominant increase in the lower bands of ECoG spectrum. Dermorphin was found significantly more potent than beta-endorphin and DALA since it was active at much lower doses. Behavioural and ECoG sleep evoked by opioid peptides were rapidly reversed by naloxone showing that these effects are mediated through an activation of specific opioid receptors. Doses of pentazocine equimolar with doses of dermorphin and beta-endorphin producing sleep did not affect behaviour and spectrum power whereas higher doses produced opposite effects, i.e., behavioural stimulation, pecking and increase in locomotor activity.