Differences in the effects of beta2- and beta3-adrenoceptor agonists on spontaneous contractions of human nonpregnant myometrium.

Both BRL 37344 and ritodrine decreased contractility of human nonpregnant myometrium, with distinct effects on contraction parameters.

• BRL 37344 and ritodrine reduced the area under the curve (AUC) values, indicating decreased contractility.
• The degree of inhibition of spontaneous contractile activity was similar for both substances, remaining under 30%.
• BRL 37344 specifically decreased the mean frequency of contractions, while ritodrine reduced the mean amplitude.
• The inhibition of contractions by BRL 37344 was partially blocked by beta-blockers bupranolol and propranolol, but not by butoxamine.
• In contrast, ritodrine's effects were counteracted by all tested beta-blockers.

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