Effects of gadolinium chloride on basal flow and compression-induced rapid hyperemia in the rabbit masseter muscle.

Aim of the present study is to investigate the role of mechano-sensitive channels on basal muscle blood flow and on the compression-induced rapid hyperaemia. To this aim, the mechano-sensitive channel blocker Gadolinium (Gd(3+)) is employed, which already proved to reduce the myogenic response in isolated vessels. Muscle blood flow (MaBF) was recorded from the masseteric artery in 8 urethane-anesthetized rabbits. Rapid hyperemic responses were evoked by 1-s lasting compressions of the masseter muscle (MC) delivered before and after close arterial infusion of Gd(3+) in the masseteric artery. Three infusions were performed at 1-h interval, producing estimated plasma concentration (EPC) of 0.045, 0.45 and 4.5 mM, in the masseteric artery. The amplitude of the hyperaemic response to MC, equal to 195±77% of basal flow in control condition, was reduced by 9.5±19.4% (p=0.18) and 45±28% (p<0.01) while basal MaBf increased by 10±3% (p=0.90) and by 68±30% (p<0.01) at EPC of 0.045 and 0.45 mM, respectively. At EPC of 4.5 mM a strong reduction in both MaBF (by 54±13%, p<0.01) and MC response (75±12%, p<0.01) was instead observed. These effects did not depend on time from infusion. At all doses employed Gd(3+) never affected arterial blood pressure, heart rate and contralateral MaBF. While the effects observed at the highest EPC likely result from blood vessel occlusion due to Gd(3+) precipitation, the effects observed at lower concentrations demonstrate that Gd(3+) affects musculo-vascular function by decreasing both resting vascular tone and responsiveness to mechanical stimuli. The results are compatible with a Gd(3+)-induced blockade of vascular mechano-sensitive channels.