Conditioned taste aversion is disrupted by prolonged retrograde effects of intracerebral injection of tetrodotoxin in rats.

Acquisition of conditioned taste aversion (CTA) is disrupted when 10 ng tetrodotoxin (TTX) is injected into both parabrachial nuclei of rats immediately after saccharin drinking and before LiCl poisoning (Ivanova & Bures, in press). Further analysis of this finding showed that parabrachial TTX injection (a) elicited retrograde amnesia also when applied 1, 2, or 4 days but not 8 days after CTA acquisition; (b) did not abolish CTA produced by 2 or 3 saccharin-LiCl pairings; (c) did not cause persistent increase of quinine threshold; and (d) elicited anterograde CTA amnesia when applied 1 but not 2, 4, or 8 days before CTA acquisition. TTX-induced amnesia is not due to persistent gustatory agnosia but rather to disruption of the protracted consolidation of the permanent CTA engram by prolonged cessation of impulse activity in the information storing network.