The effects of sucrose or fat ingestion and cocaine administration on locomotor activity and tyrosine hydroxylase in the rat

Palatable foods such as sucrose may enhance the behavioral effects of cocaine or amphetamine. Manifestation of this enhancement may indicate a cross-sensitization phenomenon parallel to the mechanism of actions of psychostimulants, such cocaine, and palatable foods, such as sucrose. Since dopamine is the major substrate linked to drug addiction, a better understanding of tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, may suggest novel mechanisms involved in the drug addiction process.; Does sucrose or a fat diet alter locomotion and tyrosine hydroxylase in the mesolimbic pathway? We demonstrated that neither fat nor a sucrose diet altered locomotion. On tyrosine hydroxylase, it was demonstrated that a fat diet significantly increased tyrosine hydroxylase in the ventral tegmental area but not in other brain regions.; Does sucrose or a fat diet influence the locomotor-activating effects of cocaine to enhance cocaine-induced locomotion and sensitization? Cocaine significantly increased locomotor activity on the 1st injection, and sensitization occurred on the 8th injection. However, neither sucrose nor a fat diet enhanced acute cocaine effects (1st injection). Although not significant, sucrose, not fat, tended to enhance cocaine-induced sensitization (8th injection).; Does the combination of a sucrose diet and cocaine, or a fat diet and cocaine affect levels of tyrosine hydroxylase? With a sucrose diet and cocaine, tyrosine hydroxylase in the medial prefrontal cortex and striatum was significantly decreased. Rats fed only chow and administered cocaine had significant decreases of tyrosine hydroxylase in the cortex. Finally, there was a significant decrease of tyrosine hydroxylase in the striatum of sucrose fed rats injected with saline; thus, supporting the theory that palatable foods can alter dopaminergic function. A fat-diet had no significant effects on tyrosine hydroxylase.; From these studies, it was demonstrated that both palatable foods and cocaine can significantly influence tyrosine hydroxylase. Although the effects of palatable food on locomotor activity are less clear, more studies merit further investigations.