Orofacial and somatic responses elicited by lithium-, nicotine- and amphetamine-paired sucrose solution.

Amphetamine and nicotine share the characteristics of both producing a conditioned taste avoidance response (CTA) via their action within the blood-brain-barrier (BBB) whereas lithium produces a CTA via its action outside of the BBB. Although, at the doses employed, all three drugs produced equally strong CTAs, amphetamine (3 mg/kg)- and nicotine (1 mg/kg)-paired 0.5 M sucrose solution elicited a similar pattern of orofacial and somatic responses which differed from that pattern elicited by a lithium (127.2 mg/kg)-paired sucrose solution. Sucrose paired with either amphetamine or nicotine elicited suppressed ingestion responses of tongue protrusion and paw licking, but did not elicit enhanced rejection responses. On the other hand, sucrose paired with lithium elicited not only suppressed ingestion responses, but also a pattern of enhanced rejection responses of chin rubbing and paw treading. The results suggest that the CTA established by lithium is qualitatively different than the CTA established by amphetamine or nicotine.