Effects of naloxone treatment on memory-enhancing properties of post-training administration of substance P.
The present study investigated the effects of post-trial systemic injections of the neurokinin substance P (SP) on inhibitory avoidance learning in rats treated with naloxone before conditioning and/or test trials. Rats were trained in a step-down or uphill inhibitory avoidance task and tested 24 h later. The animals received, 30 min before training and/or testing an i.p. injection of saline or naloxone (Nx) at doses of 0.5; 1.0; 5.0 or 50 mg/kg. Immediately after training they were administered SP 50 micrograms/kg or vehicle. Animals that received Nx both before conditioning and test trials (5.0 and 50 mg/kg), in combination with SP, showed better test performance for the uphill and step-down avoidance then those treated only with SP. Nx administered only before training (5.0 and 50 mg/kg) or before test (0.5 to 50 mg/kg) reduced the effects of SP. These data are discussed in terms of the possibility that Nx produces a state-dependent learning when combined with SP.
Silva
M
M
Laboratory of Psychobiology, FFCLRP, University of São Paulo, Ribeirão Preto, Brazil.
Nogueira
P J
PJ
Tomaz
C
C
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D008297:Male; D008568:Memory / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013373:Substance P / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects
D013373:Substance P; D009270:Naloxone