Reflex-elicited increases in female rat parotid protein synthesis involving parasympathetic non-adrenergic, non-cholinergic mechanisms

Normal rats or rats parasympathetically denervated on one side by cutting t he auriculo-temporal nerve were maintained on a liquid diet for I week. Aft er fasting overnight, experimental rats were then offered hard, pelleted fo od over a Period of 2 h, while unfed animals served as controls. The reflex -induced increase in the [H-3]leucine incorporation into trichloroacetic ac id-insoluble material of the parotid glands following intake of the food in the presence of the muscarinic blocker atropine and alpha- and beta -adren oceptor antagonists was greater (104%) than in the absence of the blockers (75%) in normal rats. The picture was the same when the innervated glands o f rats subjected to unilateral parasympathetic denervation were examined. I n this case, the protein synthesis increased by 108% in the presence of the blockers and by 63% in their absence. Analysis of the parasympathetically denervated and contralateral innervated glands revealed no support for a ch olinergic or adrenergic contribution to this response. The increase in prot ein synthesis in the innervated glands was 86% in the rats treated with atr opine, whilst it was 76% in those treated with alpha- and beta -adrenocepto r antagonists. The protein synthesis in the denervated glands increased by 57% in the absence of receptor blockade. Neither atropine (51%), nor a- and b-adrenoceptor antagonists (52%), nor a combination of the three blockers (55%) affected the response of the denervated glands. A large part of the r esponse in the presence of the traditional autonomic receptor blockers was thus dependent on the parasympathetic auriculo-temporal nerve. Under natura l feeding conditions, the parasympathetic non-adrenergic, non-cholinergic ( NANC) mechanisms are likely to contribute to the synthesis of secretory pro teins.