Background: Alverine citrate is commonly used in the treatment of painful affections of the colon.
Aim: To determine whether alverine citrate acts on the vagal sensory endings.
Methods: Unitary recordings were performed at the level of the vagal fibres in the nodose ganglion of anaesthetized cats using extracellular glass microelectrodes, and the patterns of response to chemical and mechanical stimuli applied to identified vagal intestinal mechanoreceptors were studied.
Results: The intestinal mechanoreceptors located at the endings of type C vagal fibres responded mainly to mechanical stimuli (distension and contraction), but also responded to chemical substances (cholecystokinin and substance P). The most conspicuous effect of alverine (2 mg/kg) was that it significantly inhibited the pattern of vagal activity produced in response to either cholecystokinin (5-10 microg/kg), substance P (5-10 microg/kg) or phenylbiguanide (5-10 microg/kg), a 5-HT3 receptor agonist. On the other hand, the unitary vagal response to the mechanical distension was slightly enhanced by alverine, as was any spontaneous activity present.
Conclusions: Based on the present data, alverine citrate can be said to decrease the sensitivity of the intestinal mechanoreceptors, which is consistent with its previously established anti-spasmodic effects.