Electromechanical coupling in feline basilar artery in response to serotonin.

This study was undertaken to define some of the cellular mechanisms of action of serotonin on cerebral vascular muscle. Application of serotonin to cat basilar artery resulted in a dose dependent depolarization and contraction beginning at 10(-8) M. The correlation coefficient relating the degree of force development with the change in membrane potential (Em) was 0.98. Excess K+ depolarized these vascular muscle cells with a slope (between 10 and 100 mM [K]0) of 54 mV/decade. When the muscle cells within this artery were depolarized by only 7 mV by addition of excess K+ there was a significant reduction in force development in response to serotonin. When the membrane was depolarized from -63 to -40 mV the mechanical response to serotonin was reduced by around 50%. Steady state current/voltage curves demonstrated a reduction in input resistance suggesting that serotonin's mechanism of depolarization is not due to a reduction in gk. These data demonstrate that serotonin contracts cat basilar artery through mechanisms involving vascular muscle cell depolarization and that factors which influence the level of Em will markedly effect the contractile response to serotonin.