AMPA RECEPTOR FACILITATION ACCELERATES FEAR LEARNING WITHOUT ALTERINGTHE LEVEL OF CONDITIONED FEAR ACQUIRED

Rats treated with the AMPA receptor-facilitating drug 1-(quinoxolin-6- ylcarbonyl)piperidine (BDP-12) during training acquired fear condition ing to a tone faster than vehicle-treated controls. The effect on acqu isition was dependent on the dose given. BDP-12-treated rats and vehic le-treated controls reached the same level of conditioned fear and ext inguished at the same rate. The dissociation of learning rate from the se other normally covariant measures suggests that the drug had a spec ific and isolated effect on acquisition. Controls for drug effects on stimulus sensitivity, locomotor activity, generalized fearfulness, and other performance factors support this interpretation, the known acti on of BDP-12 on receptor dynamics suggests that its effect on acquisit ion. may be attributed to specific modulation of an AMPA and NMDA rece ptor-dependent plasticity mechanism. The finding that the drug acceler ates acquisition but does not affect the level of conditioned fear acq uired parallels the effect of the drug on long-term potentiation (LTP) (increasing the rate but not the ceiling of potentiation) and suggest s that common mechanisms may underlie fear conditioning and LTP.