Cerebrocortical modulation of S2-receptors and turnover rate of 5-hydroxytryptamine in ischemia.

A possible relationship between the changes in the properties of S2-receptor binding sites and the turnover rate of 5-hydroxytryptamine (5-HT) has been investigated in cerebral ischemia associated with either little or marked edema. Bilateral common carotid artery occlusion for 5 or 15 min with 1 hour of reestablished blood flow in gerbils served as a model for the respective studies. An alteration in kinetic characteristics of S2-receptor binding sites labeled with [3H]ketanserin (the potent 5-HT antagonist for postsynaptic receptors) was detected in the synaptosomes separated from brains of gerbils subjected to 1 hour release after 15 but not following 5 min of bilateral ischemia. At the same time, an increased turnover rate of 5-HT was found in the cerebro-cortical homogenate. The duration of ischemic insult which leads to the changes in the properties of S2-binding sites and the increase in turnover rate of 5-HT has been identical with that needed for the marked accumulation of water in the gerbil brain reported previously. Thus, these findings are consistent with the implicated involvement of 5-HT in the formation of ischemic cerebral edema.