Central Cholinergic Modulation of Carrageenin-induced Pedal Inflammation in Rats.

Possible central cholinergic modulation of acute peripheral inflammation was investigated in rats, adopting the carrageenin-induced acute pedal edema as the experimental model. Intracerebroventricularly (icv) administered acetylcholine (Ach) and tremorine, a central cholinomimetic agent, significantly augmented the inflammation, whereas hemicholinium, which inhibits Ach synthesis, attenuated the edema. Paradoxically, icv administered atropine sulphate induced an Ach like pro-inflammatory effect and also failed to affect the Ach action. The atropine-induced inflammation promoting effect was annulled after hemicholinium pre-treatment, suggesting that it was dependent on the integrity of central cholinergic function. The pro-inflammatory effect of icv Ach was negated after peripheral administration of atropine ethoiodide. It is suggested that the carrageenin inflammation promoting effect of centrally administered Ach is due to enhanced peripheral cholinergic activity.