title: Changes in the responsiveness of the cat ileocecal sphincter to adrenergic agents during the postnatal period.
abstract: The changes in the responsiveness of the cat ileocecal sphincter (ICS) to adrenergic agents during the postnatal period were studied by the effect of noradrenaline (applied cumulatively: 0.01-100 mumol) on the mechanical activity:smooth muscle tone and phasic contractions. Noradrenaline contracted the ICS smooth muscle through alpha 1-adrenergic receptors. These receptors were differentiated in the first postnatal days but continue to develop functionally even after 60 days postnatal. An age-determined decrease in the EC50 values of noradrenaline, inducing tonic contractions, was established. Noradrenaline inhibited the phasic contractions of ICS. This effect increased after beta-adrenergic receptor blockers, and disappeared after blocking of alpha 1-adrenergic receptors, which suggests the existence of a postjunctional inhibitory adrenergic receptor of alpha 1 type. The beta-adrenergic receptors in the ICS smooth muscle are not differentiated until 15 days postnatal. They developed functionally towards 30 days postnatal.
mesh_terms: D000320:Adrenergic Fibers / Q000187:drug effects / Q000502:physiology*; D000367:Age Factors; D000818:Animals; D002415:Cats; D005260:Female; D007080:Ileocecal Valve / Q000187:drug effects* / Q000294:innervation; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D015016:Yohimbine; D011433:Propranolol; D009638:Norepinephrine