Food and drugs can activate brain
dopamine systems and sensitivity to the effects of drugs acting on those systems is influenced by amount and content of food consumed. This study examined the effects of drinking
sucrose on behavioral effects of the direct-acting
dopamine receptor agonist quinpirole. Male Sprague-Dawley rats (n=6/group) had free access to water or 10%
sucrose and
quinpirole dose-response curves (yawning and
hypothermia) were generated weekly for 8 weeks. Subsequently, all rats drank water for 8 weeks with
quinpirole dose-response curves determined on weeks 9, 10, and 16. In rats drinking
sucrose, the ascending (D3 receptor-mediated), but not descending (D2 receptor-mediated), limb of the yawning dose-response curve shifted leftward. The D3 receptor-selective antagonist
PG01037 shifted the ascending limb of the dose-response curve to the right in all rats. When rats that previously drank
sucrose drank water, their sensitivity to
quinpirole did not return to normal.
Quinpirole-
induced hypothermia was not different between groups. These data show that drinking
sucrose increases sensitivity to a
dopamine D3, but not D2, receptor-mediated effect and that this change is long lasting.
Dopamine receptors mediate the effects of many drugs and the actions of those drugs are likely impacted by dietary factors.