Food restriction alters pramipexole‐induced yawning, hypothermia, and locomotor activity in rats: Evidence for sensitization of D2, but not D3 receptor‐mediated effects

Abstract

It has been well established that food restriction enhances sensitivity to the reinforcing effects of drugs of abuse, and that food restriction alters a variety of behavioral and pharmacological responses to dopaminergic agonists. Evidence from behavioral and molecular studies suggests that augmented dopaminergic responses observed in food‐restricted animals result from a sensitization of the D2 receptor, however, little is known about how food restriction affects the D3 receptor. These studies were aimed at defining the effects of food restriction on D2 and D3 receptor function by assessing pramipexole(PPX)‐induce yawning, penile erection (PE), hypothermia, and locomotor activity in free‐fed and food‐restricted rats. Food restriction resulted in a suppressed level of PPX‐induced yawning, a sensitized hypothermic response, and an enhanced locomotor response to PPX; there was no effect on PPX‐induced PE. In food‐restricted rats, the D3‐selective antagonist, PG01037, inhibited PPX‐induced yawning and PE while the D2‐selective antagonist, L‐741,626, restored PPX‐induced yawning to free‐fed levels. These results suggest that food restriction sensitized rats to the D2‐mediated effects of PPX while having no effect on the D3‐mediated effects of PPX.Supported by grants DA20669 & F013771 through NIDA