“…However, in the presence of the 0-adrenoreceptor antagonist propranolol, a-adrenoreceptor mediated motor responses to NA and Adr were observed in three of the four stages of the natural oestrous cycle (oestrus, metoestrus and dioestrus, but not proestrus). Similar responses in the presence of a 0-adrenoreceptor antagonist have previously been described (Jensen & Vennerod, 1961;Brooks, Schaeppi & Pincus, 1965;Butterworth & Randall, 1970). Although Adr is nearly always inhibitory, occasionally strips of uterus from rats in oestrus, produced a motor response (Bonney & Ferguson, 1950).…”