Central enhancement of taste pleasure by intraventricular morphine

Do centrally-administered opioid agonists stimulate feeding by enhancing the palatability of foods? This hypothesis has been supported by several lines of evidence, including previous 'taste reactivity' studies of the influence of systemic morphine on affective (hedonic and aversive) behavioral reactions to taste palatability. The presents study examined whether opioid agonists enhance palatability by acting centrally on brain palatability systems. Here we report the effect of intraventricular microinjections of morphine (0, 12, 25, 50 nmols) on hedonic taste reactions to a 0.12 M sucrose solution. The effect on feeding was also assessed in order to determine whether feeding and palatability enhancement are linked, as would be required by the hypothesis that feeding is due to enhanced palatability. Both hedonic taste reactivity patterns and feeding were significantly increased together by morphine administration into the lateral ventricle. We conclude that opioid-induced enhancement of the hedonic palatability of food is a centrally mediated effect. Enhancement of food palatability may be an important psychological route by which intracranial administration of opioid agonists induce feeding.