POST-TRAINING NUCLEUS BASALIS MAGNOCELLULARIS FUNCTIONAL TETRODOTOXINBLOCKADE EFFECTS ON PASSIVE-AVOIDANCE CONSOLIDATION IN THE RAT

The tetrodotoxin (TTX) functional ablation technique was employed in o rder to evaluate the temporal coordinates of the rat's nucleus basalis magnocellularis (NBM) involvement in memory trace processing. Under k etamine general anesthesia, TTX (10 ng in 1 mu l saline) was stereotax ically administered to rats, either in one or both NBMs. TTX was injec ted to different groups of rats, respectively 15 min, 6, 24, 48, 96 h after passive avoidance acquisition testing. The rats underwent retrie val testing 48 h later, i.e. after full recovery from TTX effects. Res ults show that: (I) monolateral TTX blockade significantly impairs PAR conditioned responding if induced up to 6 h but not 24 h after acquis ition testing; (2) bilateral TTX blockade dramatically impairs passive avoidance responding up to a 48-h delay but not 96 h after acquisitio n testing. The results indicate a very profound involvement of NBM in passive avoidance response consolidation. The experimental evidence is discussed together with previous functional ablation findings concern ing amygdala, parabrachial nuclei and neocortex.