The effects of clonidine and three 2-imidazoline derivatives on the secretion of protein and some electrolytes by rat submandibular and parotid glands.

1. Three imidazoline analogues of clonidine were potent secretagogues for the parotid and submandibular glands at relatively high doses. 2. Salivation in response to clonidine was completely abolished by prazosin, phentolamine, phenoxybenzamine and dihydroergotamine. 3. The gamma-type of proteins was secreted in response to three of the analogues, whereas with p-aminoclonidine the alpha-type of proteins was secreted by the submandibular gland. 4. Albumin was specifically secreted by the submandibular gland in response to clonidine but not to isoproterenol or phenylephrine.