Orosensory self-stimulation by sucrose involves brain dopaminergic mechanisms

The most convincing body of evidence supporting a role for brain dopaminergic mechanisms in sweet taste reward has been obtained using the sham-feeding rat. In rats prepared with a chronic gastric fistula and tested with the cannula open, intake is a direct function of the palatability of the solution offered as well as of the state of food deprivation. Because essentially none of the ingested fluid passes on to the intestine, negative postingestive feedback is eliminated. Thus, the relative orosensory/hedonic potency of the food determines and sustains the rate of sham intake; long periods of food deprivation are not required. In this way, the sham feeding of sweet solutions may be considered a form of oral self-stimulation behavior and afford a preparation through which the neurochemical and neuranatomical substrates of sweet taste reward may be identified. The results obtained in the series of experiments summarized in this paper clearly indicate that central D-1 and D-2 receptor mechanisms are critical for the orosensory self-stimulation by sucrose in the rat. In conclusion, I suggest that such investigations of the roles of brain dopaminergic mechanisms in the sucrose sham-feeding rat preparation may further our understanding of normal and aberrant attractions to sweet fluids in humans (see Cabanac, Drewnowski, and Halmi, this volume), as an innate, positive affective response of human neonates to sucrose and the sustained positive hedonic ratings for glucose when tasted but not when consumed have demonstrated.