Plasma Free 5HT, Plasma 5HIAA and Whole Blood 5HT in the Rat

Abstract

Previous results from this and other laboratories (Anderson et al., 1987) showed that a free pool of serotonin (5HT) occurs in human plasma and that it can be pharmacologically differentiated after several treatments including clomipramine (Sarrias et al., 1987), lithium (Artigas et al., 1989) or carbidopa (Ortiz et al., 1988). Also, free 5HT in plasma and platelet 5HT undergo independent seasonal changes (Sarrias et al., 1989). These data suggest that, when working with human blood, it is possible to have only negligible or no contribution from platelets to free plasma 5HT. As a consequence, it is of interest to study how both 5HT pools (free and stored) are affected by pathologies in which 5HT is thought to be involved and to examine their change after drug treatment. Since 5HT uptake inhibitors (acting in CNS and in platelets) are widely used as antidepressant drugs, such a peripheral model could be useful in the study of their “in vivo” mode of action in patients and in experimental animals. In the latter, CNS changes after drug treatment can also be studied, enabling a direct comparison of CNS and peripheral effects. For that purpose, we have explored the possibility of using rat blood to study the plasma free and platelet pools of 5HT.