Clonidine, but not ritanserin, suppresses kainic acid-induced automatisms in developing rats

In young rats, systemic or local administration of kainic acid (KA) elicits scratching as the prevailing automatism whereas in adult rats, wet dog shakes (WDS) are usually recorded. We tested the effects of the alpha sub(2)-adrenergic agonist clonidine also acting, however, on imidazoline receptors), which has been reported to block KA-induced WDS in adult rats and the 5-HT sub(2) antagonist ritanserin in rats aged 7, 12, 18, 25, and 90 days treated IP with doses of KA that induce maximum number of automatisms with minimal early lethal effects. We have demonstrated that KA-induced automatisms develop from scratching in pups to prevailing WDS in adult rats, whereas the incidence of scratching rather decreases during development. As indicated by the presence of both automatisms in the same animal, we suggest that there are probably different neuronal circuits responsible for the induction of automatisms, however, both modulated by the alpha sub(2)-adrenergic or imidazoline receptor system.