[Excitatory beta-adrenoreceptors on enteral cholinergic interneurons of the large intestine and ileocecal sphincter]. / Vozbuzhdaiushchie beta-adrenoretseptory na énteral'nykh kholinérgicheskikh interneironakh tolstoi kishki i ileotsekal'nogo sfinktera.

Acute experiments were performed on the isolated intestinal loop, vascularly perfused with arterial blood by means of the constant flow perfusion pump. Contractile activity of the ileocecal sphincter and proximal parts of the large intestine was estimated by the maximal isometric tension and total (integrated) contractile activity. Isoprenaline (1-2 mg) induced contractile responses of the colonic segment and ileocecal sphincter. These responses were abolished or dramatically diminished by the blockade of beta-adrenoceptors, muscarinic, and nicotinic cholinergic receptors. Data obtained support the idea, that the large intestine and ileocecal sphincter have excitatory beta-adrenoceptors localized on cholinergic interneurones of the enteric nervous system.

[The participation of met-enkephalin in the display of contractile reactions of the large intestine and ileocecal sphincter]. / Ob uchastii met-énkefalina v proiavlenii sokratitel'nykh reaktsii tolstoi kishki i ileotsekal'nogo sfinktera.

Blockade of H-cholinoreceptors, alpha- and beta-adrenoreceptors did not lead to disappearance of the colon and ileocecal sphincter contractile responses to i.a. administration of met-enkephalin (0.05-8.0 micrograms). The responses of the colon, as well as ileum and jejunum were augmented under blockade of alpha-adrenoreceptors whereas the responses of ileocecal sphincter decreased. The latters were augmented under blockade of beta-adrenoreceptors. Met-enkephalin infused into the vascular bed of an isolated portion of the intestine (0.01-5.0 micrograms/ml/min), potentiated the colon and ileocecal sphincter responses to acetylcholine (1.0-20.0 micrograms), the colon responses to stimulation of the n. vagus efferent fibers, and the ileocecal sphincter responses to serotonin (20-100 micrograms).

[Initiating and modulating effects of met-enkephalin in the appearance of contractile reactions of the jejunum and ileum]. / Initsiiruiushchie i moduliruiushchie éffekty met-énkefalina v proiavlenii sokratitel'nykh reaktsii toshchei i podvzdoshnoi kishki.

In acute experiments on cats, an isolated loop of small intestine was vascularly perfused by means of the constant volume pump. The jejunum and ileum contractility was estimated by maximum isometric tension and total contractile activity. Neither N- nor M-cholinoreceptor blockade eliminates the contractile responses of jejunum and ileum to i.a. injection of metenkephalin. I.a. infusion of metenkephalin (10(-8)--10(-6) g/ml/min) potentiated contractile responses to acetylcholine, inhibited those to serotonin, potentiated or inhibited responses to electrical stimulation of vagal efferents. The data suggest metenkephalin to be able to modulate the contractile activity of intestinal smooth muscle, affecting the cholinergic excitatory and noncholinergic, nonadrenergic inhibitory mechanisms.

[Role of alpha- and beta-adrenoreceptors of the jejunum and ileum in displays of their contractile reactions]. / Rol' al'fa- i beta-adrenoretseptorov toshchei i podvzdoshnoi kishki v proiavlenii ikh sokratitel'noi reaktsii.

Acute experiments were performed on isolated segments of the cat small intestine vessels. The contractile activity of the jejunum and ileum was estimated by the maximal isometric tension. Blocking of the alpha-adrenoreceptors with phentolamine induced a reinforcement of the contractile reactions, whereas blocking of the beta-adrenoreceptors with propranolol led to inhibition of both jejunum and ileum contractile responses either to exogenous acetylcholine or electrical stimulation of vagal efferent fibers. The subthreshold activation of alpha-adrenoreceptors with noradrenaline induced mostly inhibition, whereas activation of beta-adrenoreceptors with isopropylnoradrenaline caused a potentiation of the contractile response to exogenous acetylcholine. The data obtained suggest existence of excitatory beta-adrenoreceptors with a presynaptic localization in the jejunum and ileum.

[Effect of activation of the cholinergic system of the small intestine on its contractile responses induced by serotonin]. / Vliianie aktivatsii kholinergicheskoi sistemy tonkoi kishki na ee sokratitel'nye reaktsii, vyzyvaemye serotoninom.

In acute experiments on cats, an isolated portion of the small intestine was vascularly perfused with arterial blood by means of the constant volume perfusion pump. Contractile activity of the ileal and/or jejunal segment was estimated by means of isometric tension. Activation of the myenteric cholinergic neurons as the result of the infusion of nicotinic cholinoreceptor agonist subecholine or electrical stimulation of the vagal efferents was followed by increased contractile response of intestinal smooth muscle to serotonin (2.5 X 10(-8) or 5.0 X 10(-9) mol). The same effect was observed after increasing endogenous acetylcholine concentration induced with application of anticholinesterase drug prozerin. The data obtained suggested that the modulating effect of acetylcholine might be of a certain physiological importance.