We examined the effects of serotonin (5-HT) on cardiovascular responses and blood flows in the right common carotid artery (RCCA), superior mesenteric artery (SMA) and right femoral artery (RFA), stimulated by glutamate (Glu) in the dorsomedial medulla (DM), rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM). Microinjection of Glu into the DM produced increases in systemic arterial pressure (SAP) and flows in the RCCA and RFA, and decrease in flow in the SMA. Microinjection of Glu into the RVLM produced increases in SAP and decreases in flows in the RCCA, SMA and RFA. Prior microinjections of 5-HT into the same sites attenuated all the Glu-induced responses. Microinjection of Glu into the CVLM produced decreases in SAP and flows in the RCCA, SMA and RFA. These decreases were potentiated by prior injection of 5-HT. These findings suggest that 5-HT modulates the cardiovascular and blood flow responses induced by Glu in the medulla.
