Sympathetic control of the coronary circulation during trigeminal nerve stimulation in humans

We sought to investigate the sympathetic mechanism controlling coronary circulation during trigeminal nerve stimulation in healthy women.

The protocol consisted of 3 min of trigeminal nerve stimulation (TGS) with cold stimuli to the face, in two conditions: (1) control and β-blockade (oral propranolol), and (2) control and α-blockade (oral prazosin).

Thirty-one healthy young subjects (women: n = 13; men: n = 18) participated in the study. By design, TGS decreased heart rate (HR), and increased blood pressure (BP) and cardiac output (CO). Before the β-blockade coronary blood velocity (CBV-Δ1.4 ± 1.3 cm s^-1) increased along with the decrease of coronary vascular conductance index (CVCi-Δ-0.04 ± 0.04 cm s^-1 mmHg^-1) during TGS and the β-blockade abolished the CBV increase and a further decrease of CVCi was observed with TGS (Δ-0.06 ± 0.07 cm s^-1 mmHg^-1). During the α-blockade condition before the blockade, the CBV increased (Δ0.93 ± 1.48 cm s^-1) along with the decrease of CVCi (Δ-0.05 ± 1.12 cm s^-1 mmHg^-1) during TGS, after the α-blockade CBV (Δ0.98 ± cm s^-1) and CVCi (Δ-0.03 ± 0.06 cm s^-1 mmHg^-1) response to TGS did not change.

Coronary circulation increases during sympathetic stimulation even with a decrease in heart rate.