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Male and female rats with ad lib access to separate sources of carbohydrate, fat, and protein were implanted with minipumps providing one of three dosages (0.0, 40.0, or 80.0 mg/kg/day) of phenylpropanolamine (PPA) for 2 weeks. Body weight, macronutrient intake, and water consumption were measured daily before, during, and after PPA treatment. Phenylpropanolamine lowered body weight and caloric intake in males and females, and water consumption in females, but did not alter dietary composition in either sex. After PPA termination, caloric intake returned to control levels in both males and females. However, body weight returned to control levels in males only, while PPA-treated females continued to weigh less than controls. Phenylpropanolamine termination was associated with significant increases in water consumption and the percentage of total calories consumed from protein and reductions in the percentage of calories from carbohydrate in males. In contrast, water and macronutrient consumption was similar comparing PPA-treated females to controls after drug termination. These results suggest there are sex differences in the effects of PPA termination on water and macronutrient consumption that result in differential weight gain in males and females.

This experiment examined the effects of phenylpropanolamine (0.0, 5.0, 10.0, 20.0 mg/kg PPA) on regulatory (RG) and nonregulatory (NRG) eating and drinking in rats using a within-subjects design. Administration of PPA produced dose-dependent reductions in eating in animals deprived to 80-85% of baseline weight, and reduced drinking after 23.5-h of water deprivation. Nonregulatory eating, elicited by tail pinch in nondeprived animals, was similarly inhibited. Nonregulatory drinking was elicited in the schedule-induced polydipsia (SIP) paradigm. Water consumption, locomotion, licking, lick efficiency (licks/ml water), and entries into the food magazine were simultaneously measured. At the lowest dose, only locomotion was significantly reduced. At 10.0 mg/kg, lick efficiency and entries into the food magazine were also significantly reduced, while all measured behaviors, including licking and water consumption, were decreased by the highest dose of PPA. The reduction in lick efficiency suggested a PPA-induced motor impairment in the capacity for licking. Considered together, these results indicated that the observed decreases in regulatory and nonregulatory eating and drinking could be at least partially accounted for by the drug's effects on behaviors contributing to ingestion, as well as apparent motor impairments in ingestive behavior at higher doses.