[Opioid receptors in the brain related to behavior]

The effects of opioid peptides selective for opioid receptors on drinking, dopamine-related behavior, discriminative stimulus and memory processes were investigated in detail. Mu opioid receptors in the paraventricular nucleus of hypothalamus played an important role in drinking behavior. The stimulation of mu and kappa opioid receptors inhibited dopamine D2 receptor-related behavior. The discriminative stimulus effects of morphine and pentazocine were mediated through mu opioid receptors, while the stimulus effects of cocaine through delta opioid receptors. Mu opioid agonists elicited memory dysfunctions, whereas kappa opioid agonists such as dynorphin A-(1-13) improved amnesia induced by ischemia, basal forebrain-lesion or scopolamine. It appears that opioid receptors are fully involved in the neural basis of behavioral responses.