[Role of cholinergic and adrenergic mechanisms in the development of contractile responses of the small intestines to bradykinin].

In anesthetized cats with i. a. perfusion of isolated small intestine segments, the blockade of N-cholinoreceptors with benzohexonium of M-cholinoreceptors with atropine reduced jejunum and ileum contractility induced by bradykinin. After an alpha-adrenoreceptor blockade induced by phentolamine, an increase of responsiveness to bradykinin was evident whereas noradrenaline stimulation reduced the contractility. The blockade of beta-adrenoreceptors with propranolol as well as their stimulation with isopropylnoradrenaline also reduced small intestine contractility. The bradykinin-induced contractions of the small intestine segments seem to be due to the direct action of bradykinin on the smooth muscle cells and to the stimulating effect of acetylcholine released from the efferent cholinergic neurons. These effects can be modulated with catecholamine because of its influence on the excitatory presynaptic beta-adrenoreceptors and inhibitory postsynaptic alpha- and beta-adrenoreceptors.