[Y1 receptors mediate inhibitory and stimulatory effects of peptide YY in isolated small intestine and large intestine muscles of the rabbit].

Peptide YY has been shown to have stimulatory and inhibitory effects on gastrointestinal motility. However, the receptors mediating these effects are unknown. To determine if specific YY receptor agonists can mediate the effects on gastrointestinal motility we studied the effects of peptide YY (PYY), of Pro34PYY, a selective Y1 agonist, and of PYY 3-36, a selective Y2 agonist, on the motility in isolated smooth muscle strips from rabbit small and large intestine. In strips from distal colon, PYY stimulated spontaneous motility whereas it inhibited spontaneous contractions in circular strips from distal ileum. In distal circular colon maximal inotropic response (10.1 +/- 2.1% of a maximal response to carbachol 10(-5) M) was found at PYY 10(-8) M; (ED50 3.1 +/- 1.2 x 10(-9) M). In distal circular ileum maximal inhibition (by 39 +/- 20% of basal motility index) was found at 10(-7) M; (ID50 6.2 +/- 1.4 x 10(-9) M). PYY caused a dose-dependent inhibition of the on-contraction induced by electrical field stimulation. This inhibition could not be reversed by alpha- or beta-adrenergic blockade. PYY had no influence on the inotropic response evoked by carbachol. Both the stimulatory effect of PYY observed in distal colon and the inhibitory effect in distal ileum could be reproduced by the Y1 agonist Pro34PYY, but not by the Y2 agonist PYY 3-36. In distal circular colon the maximal inotropic response evoked by the Y1 agonist was 10 +/- 1.4%; (ED50 1.2 +/- 0.5 x 10(-8) M).(ABSTRACT TRUNCATED AT 250 WORDS)