Abstract:

Objective To investigate the effects of benzamil, amiloride and ruthenium red(RR) on the activity of carotid sinus baroreceptor and to probe into the properties of the mechanosensitive ion channels in arterial baroreceptor.
Methods The carotid sinus nerve discharge(CSND) was recorded from rabbit carotid sinus-nerve preparations in vitro with doubly perfusing the sinus internally and externally while the intrasinus pressure was clamped. The effects of the above-mentioned chemicals on the baroreceptor discharge were investigated.
Results Benzamil blocked CSND dose-dependently with IC50=18.5 μmol/L. The effect was reversible after washing out. Amiloride(2 mmol/L) inhibited the nerve activity reversibly by 95%. RR(100 μmol/L) blocked CSND irreversibly by 89%.
Conclusion Benzamil, amiloride and RR could block the baroreceptor activities of both type A and type C nerve endings, implying that similar mechanosensitive ion channels might locate in the two types of receptors. However, the relevant mechano-electrical transductive molecule remains to be clarified.

Key words: baroreceptor, benzamil, ruthenium red, mechanosensitive channel, epithelial sodium channel, acidsensitive channel