Nitric oxide modulates lithium-induced conditioned taste aversion

Nitric oxide (NO) has been shown to affect the behaviour in animal models o f depression, anxiety and avoidance learning. Lithium has marked effect in avoidance learning, an effect that can be modulated via the 5-HT system. Ex periments were carried out using the conditioned taste aversion (CTA) parad igm to investigate whether administration of NO-modifying drugs, serotonerg ic drugs and lithium, alone or in combination, induced or affected a CTA. T he NO-precursor L-arginine (L-Arg), the non-specific inhibitor of NOS and g uanylate cyclase, methylene blue (MB) and the specific NOS inhibitor 7-Nitr oindazole (7-NI) all produced CTAs in a dose-dependent fashion. Furthermore , we found that L-Arg counteracted the CTAs induced by LiCl or MB but faile d to modulate the CTA produced by;7-NI. The administration of the selective 5-HT,, agonist, 8-OH-DPAT, counteracted the CTAs produced by MB and 7-NI. In contrast, depletion of 5-HT by p-Chlorophenylalanine did not affect the aversions produced by MB and 7-NI, but counteracted the CTA produced by L-A rg. Our results suggest that NO plays a role in the acquisition of the CTA induced by LiCl. Furthermore, the results suggest that the 5-HT1A receptor plays an important role in the CTA induced by MB and 7-NI, thus indicating a possible interaction between the 5-HT and NO systems. (C) 2001 Elsevier S cience B.V. All rights reserved.