Is VIP the putative non-cholinergic, non-adrenergic neurotransmitter controlling protein secretion in rat lacrimal glands?

In the combined presence of cholinergic and adrenergic antagonists, electrical field stimulation (FS) caused a marked reversible increase in protein output from superfused rat lacrimal gland segments. The FS-evoked protein output was abolished by the nerve blocking drug tetrodotoxin (TTX; 10(-6) M) whereas high potassium (K+; 100 mM) continued to elicit secretion. Vasoactive intestinal polypeptide (VIP), but not adenosine 5'-triphosphate (ATP), stimulated protein secretion in a manner almost identical to that observed in response to FS. The results suggest that the non-cholinergic, non-adrenergic secretory response may involve VIP as an endogenous neurotransmitter.