3-H-ketanserin (serotonin type 2) binding in the rat frontal cortex: effect of immobilization stress

The number of 3H-ketanserin (5-HT2) binding sites in rat frontal cortex was estimated in groups of male rats subjected to a single or repeated immobilization stress (IMO). After an acute IMO for 30 or 120 min the number of 5-HT2 binding sites was significantly increased. Similar increase was found even in a group subjected for 120 min IMO for 6 consecutive days and then allowed 24 h rest (i.e. repeatedly stressed controls). If similarly treated animals were subjected to 30 min IMO after 24 h rest, the number of binding sites was increased compared to repeatedly stressed controls, but this was not the case after 120 min IMO. No significant changes of 5-HT2 receptor affinity to 3H-ketanserin were found. The changes of the ratio of 5-hydroxyindolacetic acid/5-hydroxytryptamine were similar to those of binding sites. It was concluded that the enhanced number of cortical 5-HT2 receptor binding sites may result from accelerated serotonin turnover induced by stress, but the results did not indicate any direct association between the serotonin turnover and 5-HT receptor function in the rat frontal cortex.