The β‐adrenoreceptors mediating uterine relaxation throughout the oestrous cycle of the rat are predominately of the β2‐subtype

Abstract

1 The .beta.-adrenoreceptor subtype(s) mediating uterine relaxation throughout the 4-day oestrous cycle of the rat were determined by using pharmacological techniques. 2 The order of potency of the test .beta.-adrenoreceptor agonists in dioestrus, proestrus, oestrus and metoestrus was the same, being isoprenaline = fenoterol > salbutamol > noradrenaline > prenalterol > BRL 28410. 3 The pA2 values for the antagonists atenolol and ICI 118551 against both noradrenaline and fenoterol were not altered by the stage of oestrus and were consistent with the receptor being solely of the .beta.2-subtype. 4 It is concluded that the .beta.-adrenoreceptors mediating uterine relaxation are of the .beta.2-subtype throughout the natural oestrous cycle.