The effects and selectivity of β-adrenoceptor agonists in rat myometrium and urinary bladder

Both BRL 37344 and ritodrine effectively inhibited oxytocin-induced contractions in isolated rat myometrial strips.

• The selective beta(3)-adrenoceptor agonists BRL 37344 and ritodrine produced potent inhibition of contractions in the myometrium, with pD(2) values of 6.79 and 6.89, respectively.
• Cumulative concentration-response curves for BRL 37344 and ritodrine were significantly affected by the selective beta(2)-adrenoceptor antagonist ICI 118551, shifting 10 to 30-fold to the right.
• In detrusor strips, BRL 37344 and CL 316243 also showed potent inhibition (pD(2) values of 8.51 and 8.61), while ritodrine demonstrated significantly lower potency (pD(2)=5.83).
• Pretreatment with the non-selective beta-adrenoceptor antagonist bupranolol significantly reduced responses to all agonists tested.
• Only ritodrine's response was notably affected by ICI 118551, suggesting distinct mediation pathways between the myometrium and detrusor.

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