Measurement of chloride flux associated with the myogenic response in rat cerebral arteries

1. Self-referencing ion-selective (SERIS) electrodes were used to measure the temperature and pressure dependence of Cl- efflux, during myogenic contraction of pressurized rat cerebral resistance arteries. 2. At room temperature (18-21 degreesC), a small, pressure-independent Cl- efflux was measured. On warming to 37 degreesC, arteries developed pressure-dependent myogenic tone, and this was associated with a pressure-dependent increase in Cl- efflux (n = 5). 3. Both myogenic tone and the pressure- and temperature-dependent Cl- efflux were abolished on application of 10 muM tamoxifen, a Cl- channel blocker (IC50 3.75 +/- 0.2 muM). Tamoxifen (10 muM) also prevented contraction to 60 inns K+, suggesting non-specific effects of tamoxifen (n = 5). 4. Myogenic tone was abolished by 2 pm nimodipine, but Cl- efflux was unaffected. In the presence of nimodipine, 10 muM tamoxifen still abolished pressure- and temperature-dependant. Cl- efflux (n = 3). 5. In summary, a Cl- efflux can he measured from rat cerebral arteries, with a temperature dependence that is closely correlated with myogenic contraction. We conclude that Cl- efflux through Cl- channels contributes to the depolarization associated with myogenic contraction.