ENHANCED GLUTAMATERGIC NEUROTRANSMISSION FACILITATES CLASSICAL-CONDITIONING IN THE FREELY MOVING RAT

Centrally active drugs that enhance alpha-amino-3-hydroxy-5-methyl-4-i soxazole propionic acid receptor-gated currents by increasing the ampl itude and duration of fast, excitatory synaptic responses in the hippo campus have recently been described. The effects of the compound 1-(1, 3-benzodioxol-5-ylcarbonyl) perperidine (BDP) on associative and non-a ssociative aspects of the classically conditioned eyeblink response in the freely moving rat were examined. Rats injected with BDP blinked s ignificantly more to an acoustic stimulus of 85 dB than did vehicle co ntrols, indicating that the drug enhances alpha responding to discrete auditory cues. Using a less intense stimulus of 80 dB, rats injected with BDP did not exhibit alpha responding or pseudo-conditioning, yet learned the conditioned response at a facilitated rate. These results suggest that increasing excitatory neurotransmission enhances the proc essing of sensory information and may contribute to subsequent conting ency detection.