Effect of graded doses of methysergide on basal and pentagastrin stimulated gastric secretion in anaesthetised rats.

ABSTRACT

The effect of continuous infusion (iv) of graded doses of methysergide (0.1-50 microgram(s)/kg/hr) was studied on basal and pentagastrin (5 microgram(s)/kg/hr) stimulated gastric acid secretion in anaesthetised rats by the slow, continuous stomach perfusion method. Both basal and pentagastrin stimulated acid secretion indicated a biphasic response. Methysergide induced stimulation at a lower dose of 1 microgram(s)/kg/hr and inhibition at higher doses of 20-50 microgram(s)/kg/hr. The stimulatory effect may be due to postsynaptic receptor blockade while the inhibitory effect at higher dose may be due to blockade of presynaptic 5-HT autoreceptors, or due to a direct inhibitory effect of unknown basis.