Possible role for endogenous opiates in the regulation of food intake in the newborn rat.
The possible role of endogenous opiates in the regulation of food intake was investigated by studying their influence on body weight of rat pups. Subcutaneous injection of the opiate antagonist Mr 1452 to non-deprived 1 day old rats (1-4 mg/kg) and 1.5 hr deprived 5 day old rats (2-8 mg/kg) inhibited feeding. Its stereoisomer Mr 1453 increased intake when injected to nondeprived 1 day old rats (1-4 mg/kg), but was ineffective in altering feeding behavior in 1.5 hr deprived 5 day old rats (2-8 mg/kg). Subcutaneous injection of another opiate antagonist, levallorphan (6 and 9 mg/kg), to 3 hr deprived rats also decreased intake, while its stereoisomer dextrallorphan (3-9 mg/kg) was inactive in the same experimental conditions. Subcutaneous injection of the opiate agonist met5enkephalin (16 and 32 mg/kg) to 1.5 hr deprived 5 day old rats increased feeding but leu5enkephalin (8 and 16 mg/kg) did not alter feeding behavior in the same condition. Taken together, these findings suggest a role for endogenous opiates in the facilitation of feeding in the newborn rat.
Lal
K J
KJ
Institut de Pharmacologie, Université de Lausanne, Switzerland.
Sewell
R D
RD
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001575:Benzomorphans / Q000494:pharmacology; D001835:Body Weight; D004435:Eating / Q000502:physiology*; D004723:Endorphins / Q000502:physiology*; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D007279:Injections, Subcutaneous; D007977:Levallorphan / Q000494:pharmacology; D051381:Rats
D001575:Benzomorphans; D004723:Endorphins; D004745:Enkephalins; D007977:Levallorphan; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C029552:Mr 1452