Adenosine receptor agonists inhibit TRH-induced behaviour in rabbits: evidence for a main role of striatal A2 receptors.

The present article studies the influence of A2 (CGS 21680) and A1 (CPA) adenosine receptor agonists on TRH-induced behavioural excitation in rabbits. The results show that CGS 21680 was the most effective drug when administered into the nucleus caudate, while its intracerebroventricular (i.c.v.) administration did not influence the effects induced by TRH. Conversely, CPA exerted the same, slight effects after either intracaudate or i.c.v. administration. Since TRH-induced excitatory effects can be regarded as dopamine-related behaviours, the present results further confirm that the adenosine system inhibits the behavioural effects due to dopaminergic activation. The major involvement of striatal A2 receptors in this effect of adenosine is also discussed.