The facilitatory effects of α-adrenergic drugs on neuromuscular transmission has been studied in the curarized rat phrenic-hemidiaphragm. The reversal effect of blocking action of (+)-tubocurarine on indirectly-induced twitch by α-adrenergic agents was higher with noradrenaline (EC50 = 6.51 ± 0.18 μM) compared with adrenaline (EC50 = 11.80 ± 1.06 μM) or phenylephrine (EC50 = 17.36 ± 1.02 μM). Methoxamine, clonidine and azepexol showed no effect. The action of noradrenaline was blocked by prazosin (IC50 = 3.96 ± 0.76 nM) and tolazoline (IC50 = 10.30 ± 0.5 nM) but not by yohimbine at the concentration range 0.01-0.1 μM. From these results it could be concluded that an α1-adrenergic mechanism might be involved in the facilitatory action of α-adrenergic agents at the level of motor nerve terminals.
|Journal||Archives Internationales de Pharmacodynamie et de Therapie|
|Publication status||Published - 1 Jan 1988|