Cholecystokinin reduces ingestive taste reactivity responses to water in fluid-replete but not fluid-deprived rats.

The effects of hydrational factors on the ability of cholecystokinin (CCK) to alter taste reactivity responses to intraoral water infusions was assessed in fluid-replete and fluid-deprived rats. Naive male rats were injected with CCK (8 micrograms/kg, IP), or physiological saline (1 ml/kg, IP) and taste reactivity responses elicited by brief (30 s) intraoral water infusions at 2, 4, 6, 8, and 10 min postinjection were measured. One week later and following a 24 h water deprivation period, taste reactivity responses to intraoral water infusions were measured again. Exogenous administration of CCK was found to produce a significant decrease in the frequency of ingestive responses accompanied by a significant increase in passive drip during oral water infusions in fluid-replete rats. In contrast, CCK was found to have no effect on the frequency of taste reactivity responses when rats were subjected to a period of water deprivation. These results demonstrate that the rat's state of hydration interacts with the ability of CCK to alter taste reactivity responses to intraoral water infusions.