title: The effect of altering the external Ca++ concentration and TMB-8 on noradrenaline-induced contractions of the rat anococcygeus muscle.
abstract: The effect of varying external Ca++ concentration and 8(-N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) on noradrenaline-induced contractions of the rat anococcygeus muscle was studied. The contractile response to NA was not significantly altered when the external Ca++ concentration was reduced by 50% and 75%. The contractions were however reduced to approximately 10% of the control on complete withdrawal of extracellular Ca++. The loss of contractile response to NA in O-Ca++ was time-dependent and the rate was not modified by EGTA (0.1 mM). There was a rapid restoration of NA responses on re-introducing Ca++. NA-induced contractions were concentration-dependently antagonized by TMB-8, an intracellular Ca++ antagonist. The results are interpreted to suggest that alpha 1-adrenoceptor activation in the rat anococcygeus muscle releases Ca++ from intracellular stores.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats
chemical_list: D002121:Calcium Channel Blockers; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D004110:Diltiazem; D002118:Calcium; D009638:Norepinephrine