The influence of 2-(2,6-dichlorphenylamino)-2-imidazoline hydrichloride (clonidine) and some related compounds on gastric secretion in the anaesthetized rat

Drugs tested on the anesthetized rat were: clonidine, naphazoline, xylometazoline, tolazoline, and phentolamine. Clonidine, naphazoline, xylometazoline and tolazoline produced a dose dependent stimulation of gastric acid secretion. The effect was probably not related to the influence of these drugs on haemodynamics. Phentolamine did not increase gastric acid secretion.

The increased production of gastric acid was hardly affected by atropine but was considerably reduced after pretreatment with hexamethonium. Only the effect of tolazoline was completely blocked by atropine.

Clonidine was less effective in the anaesthetized guinea pig than in the rat.

Clinidine did not affect gastric secretion in the despinalized (pithed rat). The response to histamine was also markedly reduced.

The stimulatory effect of clonidine and related drugs in the anaesthetized rats is possibly caused by a histamine-like action or by the liberation of histamine. Ganglionic stimulation may also contribute. In conscious animals the decreased gastric secretion resulting from treatment with clonidine is probably of central origin.