NONADRENERGIC, NONCHOLINERGIC INFLUENCES ON PAROTID ACINAR DEGRANULATION IN RESPONSE TO STIMULATION OF THE PARASYMPATHETIC INNERVATION IN THE ANESTHETIZED RAT

In pentobarbitione-anaesthetized rats the parasympathetic auriculotemp oral nerve of the parotid gland was continuously stimulated at suprama ximal Voltage and at maximal frequency (40 Hz) for salivary secretion. The animals were pretreated with phentolamine and propranolol (2 mg k g(-1) I.P. of each) and, in some groups, additionally with atropine (2 mg kg(-1) I.P.). Morphometric assessment at the light microscopic lev el (x 100) showed that the numerical density of parotid acinar secreto ry granules (per 100 mu m(2) acinar epithelial cytoplasm) was reduced by 30 and 39 % after 40 and 80 min, respectively, of stimulation in no n-atropinized animals and by 30 and 27 % in atropinized animals. The n umerical density of acinar granules was not influenced by pretreatment with the protein synthesis inhibitor cycloheximide. The results sugge st that most of the parasympathetic nerve-induced degranulation in the absence of muscarinic receptor blockade can be attributed to the acti on of non-adrenergic, non-cholinergic mechanisms.