An increase in intraocular pressure due to clonidine

The rise in intraocular pressure (IOP) observed after the administration of clonidine into the carotid arteries was studied in anesthetized rats and cats. This increase of IOP proved to be blocked by the alpha-sympathicolytic agent piperoxane and by the muscle relaxants d-tubocurarine and gallamine. Our experiments suggest that the elevation of IOP after clonidine injection is due to contraction of the eyelids and extraocular muscles. In these tissues alpha-adrenoceptors seem to play a part.