The effects of dose and repeated administration on the longer-term hypophagia produced by amphetamine in rats.
Rats are hypophagic approximately 1-3 and 13-27h after receiving amphetamine (2.0mg/kg). This study examined how these short- and longer-term phases of hypophagia were affected by repeated administration of different amphetamine doses. Throughout eight five-day tests, the rats could lever press for food pellets for 1-hour periods beginning every three hours. On test day 1, the rats were treated with saline, and on test day 3, they were treated with a dose of amphetamine. Across tests, for one group, treatment on day 3 alternated between 0.0 (saline) and 0.5mg/kg amphetamine; for a second, group treatment on day 3 alternated between 1.0 and 2.0mg/kg amphetamine; and for a third group, treatment on day 3 was always 1.0mg/kg amphetamine. The patterns of food intake following day 1 saline and day 3 treatment were compared. Short-term food intake was abolished by 0.5, 1.0, and 2.0mg/kg amphetamine, and no tolerance was observed to this effect. Longer-term hypophagia was produced by 1.0 and 2.0 but not by 0.5mg/kg. Tolerance to longer-term hypophagia was seen when 1.0mg/kg alone was used as the day 3 treatment, but not when 1.0 and 2.0mg/kg were alternated across tests as the day 3 treatment. Short- and longer-term hypophagia were dissociated by threshold doses for elicitation and by differential tolerance. Occasional receipt of a higher amphetamine dose may sometimes increase the longer-term hypophagia produced by a lower dose.
White
Wesley
W
Department of Psychology, Morehead State University, Morehead, KY 40351, United States. w.white@moreheadstate.edu
Hundley
Marcus B
MB
White
Ilsun M
IM
D000818:Animals; D000855:Anorexia / Q000139:chemically induced* / Q000523:psychology*; D001067:Appetite Depressants / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D004435:Eating / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D001067:Appetite Depressants; D003913:Dextroamphetamine