Abstract
This study was designed to determine whether in the submandibular glands of the rat, subjected to chemical sympathectomy with reserpine administration, a model animal of cystic fibrosis, at a dose of 5mg/kg for one day (Group 1), two days (Group 2) and at a dose of 0.5mg/kg once a day for 6 consecutive days (7 day-Group; Group 3), p-and m-octopamines, and dopamine used at different doses (10, 20, 50 and 100mg/kg) acted completely or partially as false neurotransmitters, as seen in tyramine at all doses used.
Enlargement of the submandibular glands induced by reserpine treatment was completely stopped by pargyline, a monoamine-oxidase inhibitor. The volume of saliva secreted by the submandibular glands of reserpinized rats was significantly reduced in response to m-octopamine at all days and dopamine at almost all days and all doses used, whereas in response to p-octopamine it was significantly reduced only at low doses and in combination with prazosin, but not other blockers. The total output of protein secreted, whether expressed as mg/h or μg/mg/h, by the reserpinized submandibular glands was significantly reduced in response to m-octopamine at all days after reserpine treatment. In contrast, it significantly increased at 7 days after reserpine treatment in response to dopamine and p-octopamine alone, and to p-octopamine with atropine. However, no replacement was observed in the types of proteins in the submandibular saliva of reserpinized rats in response to the three sialogogues used at any dose and with any blockers except prazosin.
These results suggest that two octopamines and dopamine could be partially false neurotransmitters and have dual actions, direct and indirect, to the salivary glands of rats.
