The mechanism of steroid anaesthetic (alphaxalone) block of acetylcholine-induced ionic currents

Open Access
Publisher Website
Google Scholar
Abstract
1 The effects of the steroid anaesthetic alphaxalone on acetylcholine (ACh)-induced ionic channels were studied in voltage clamped ‘myoballs’ in culture. 2 Alphaxalone produced a reversible blockade of the ACh-evoked inward current, ED50 = 6.0 μM. 3 The ACh reversal potential (−5.0 mV), the single channel conductance (13.5 pS) and mean open time (3.6 ms) were unchanged by the drug. Thus, alphaxalone produced an ‘all or none’ block of the ionic channel. 4 In double pulse conditioning experiments, alphaxalone produced an additional inhibition with a time constant of recovery (550 ms) much longer than the time constant of recovery of the normal desensitization (250 ms). 5 It was concluded that alphaxalone blocks active (open) ionic channels.