Substance P and naloxone enhancement of avoidance conditioning in rats.
Experiments were carried out to investigate the effects of peripheral post-training administration of substance P (SP) and naloxone on learning. Rats were trained in three different avoidance tasks (uphill, step-down and alcove) and tested 24 h later. Thirty minutes before each trial (training and testing) rats received naloxone (0.5, 1, 5, or 50 mg/kg, ip) or saline. SP (50 micrograms/kg) or vehicle was administered ip immediately after training. Animals that received SP and SP in combination with naloxone (5 and 50 mg/kg) showed significantly better retention test performance for the uphill and step-down avoidance (P less than 0.05 when compared to control rats treated with vehicle). In the alcove task no influence of SP and/or naloxone was demonstrable, probably due to a ceiling effect. These results suggest that the memory enhancement effects observed are mediated, at least in part, via interactions between substance P and the endogenous opioid systems.
Nogueira
P J
PJ
Laboratório de Psicobiologia, Faculdade de Filosofia, Universidade de São Paulo, Ribeirão Preto, Brasil.
Tomaz
C
C
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012153:Retention, Psychology / Q000187:drug effects*; D013373:Substance P / Q000494:pharmacology*
D013373:Substance P; D009270:Naloxone