Effects of paraventricular hypothalamic microinjections of phenylpropanolamine and d-amphetamine on mash intake in rats.

The present experiment compared the effects of unilateral microinjections (40, 80 and 160 nmol/0.5 microliter) of phenylpropanolamine (PPA: d,l-norephedrine) and d-amphetamine sulfate within the paraventricular hypothalamus (PVN) on consumption of a palatable sweetened-mash diet in 15-hour food-deprived adult male rats. Intracranial microinjections were administered 5 minutes prior to each 30-minute feeding trial. PPA, at a dose of 160 nmol, suppressed feeding by 42%, whereas a similar dose of amphetamine suppressed feeding by 49%. Amphetamine or PPA doses of 40 and 80 nmol were without significant effect on feeding behavior. A relatively high dose of 160 nmol amphetamine was required to suppress feeding after injection into the PVN whereas much lower amphetamine concentrations are required to suppress feeding after injection into the perifornical hypothalamus. In contrast, PPA has some anorexic activity within the PVN but not within the perifornical hypothalamus.