Cerebrovascular response to infused 5-hydroxytryptamine in the baboon. Part 1. 5-Hydroxytryptamine infusion.

Cerebral blood flow was measured in 17 baboons before and during infusion of 5-hydroxytryptamine (5-HT) into the internal carotid artery. The mean values for total cerebral blood flow, grey matter flow, and white matter flow before 5-HT infusion were 40.8, 59.2, and 12.7 ml/min/100 gm of tissue, respectively. There was no significant alteration in total blood flow or flow through grey matter when 5-HT was infused at dosages ranging from 0.5 to 10.0 microng/kg/min. A small but significant decrease in white matter blood flow was recorded when 5-HT was infused at a rate exceeding 2.5 microng/kg/min. The study indicates that in vivo, with the xenon clearance method, intra-arterial infusion of 5-HT does not significantly alter cerebral blood flow.