INVOLVEMENT OF 5-HT2 RECEPTORS IN POSTHYPOXIC STIMULUS-SENSITIVE MYOCLONUS IN RATS

We have previously reported that rats exhibited audiogenic myoclonus a t 3 days after cardiac arrest. This phenomenon peaked at 14 days, grad ually tapered off at older ages, and disappeared in most rats by 60 da ys following cardiac arrest. Because treatment with the 5-HT2-selectiv e agonist, (+/-)-1-2,5-dimethoxy-4-iodophenyl-2-aminopropane (DOI) sig nificantly attenuated audiogenic myoclonus in these postcardiac-arrest rats, the involvement of 5-HT2 receptors in posthypoxic stimulus-sens itive myoclonus was suggested. In the current study, we, therefore, ex amined the binding properties of 5-HT2 receptors in the rat bain at va rious time points following cardiac arrest. The affinity constant of [ H-3]ketanserin binding to 5-HT2 receptors in cortical membranes of rat s did not change. In contrast, B-max values were found to be reduced a t 3 and 14 days after cardiac arrest with some recovery after 60 days. Taken together with previous results, these results indicate that hyp oactivity of central 5-HT2 neurotransmission may underlie the developm ent of posthypoxic stimulus-sensitive myoclonus in rats.