Posttraining presentation of a flashing light alters retrieval of a two-way active avoidance task in rats.
Rats were trained and tested in a two-way active avoidance task (30 trials, 0.4-mA footshock, 24-h training-test interval). Exposure to an open field with flashing light (60-W lamp, 30 Hz, for 7 min, OFL) 2 h after training caused a retrieval impairment for the avoidance task, a phenomenon called retroactive interference. Animals familiarized with the OFL 24 h before training showed no retrieval impairment when exposed to the OFL 2 h after training. Both adrenal medullectomy (performed 7 to 14 days before training) and dexamethasone treatment (2 mg/kg, injected IP 24 h and 12 h before training) prevented the OFL interfering effect. Time-course experiments revealed that OFL presented either 1 or 4 h after training caused no retrieval deficit, and that animals exposed to the OFL 2 h after training and receiving another OFL presentation 1 or 2 h, but not 4 h, prior to testing had normal retrieval performance. These results suggest: 1) that the retroactive interference caused by presentation of OFL 2 h after training is due to failure of retrieval of the avoidance task since it is counteracted by the pretest presentation to the OFL, 2) that the OFL-induced retrieval interfering effect partly depends on the novelty of the OFL situation, and on the functional integrity of pituitary ACTH and adrenomedullar-dependent mechanisms and 3) that there are different mechanisms involved in posttraining and pretest OFL effects since they present distinct time-courses.
Netto
C A
CA
Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil.
Valentè
J T
JT
Borges-Sobrinho
J B
JB
Walz
R
R
Tomaz
C A
CA
D000313:Adrenal Medulla / Q000502:physiology; D000324:Adrenocorticotropic Hormone / Q000502:physiology; D000818:Animals; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D001288:Attention / Q000187:drug effects / Q000502:physiology; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D003907:Dexamethasone / Q000494:pharmacology; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone