RESUMO
<p><b>OBJECTIVE</b>To determine the mechanism of inhibitory effect of botulinum toxin type A (BTX-A) on parotid gland secretion.</p><p><b>METHODS</b>Female Wistar rats (n = 18) were randomly divided into saline injection group (n = 6) and BTX-A injection group ( n = 12), respectively. 0.1 ml of saline was injected into left parotid gland and 2.5 U of BTX-A injected into right parotid gland. Rats were sacrificed at day 7, 12 and 35 post-injections respectively for morphology and vasoactive intestinal polypeptide (VIP) immunoreactivity of parotid gland.</p><p><b>RESULTS</b>Following BTX-A injection, some atrophic cells and reduction of number of VIP-immunoreactive (VIP-IR) fibers were found in gland and tube at day 7 (P < 0.05); at day 12, there was more obvious reduction of VIP-IR fibers around tube and vessels and atrophy of cells in BTX-A injection gland than saline injection gland (P < 0.001); at day 35, the glandular cells and VIP-IR fibers were similar to saline injection group.</p><p><b>CONCLUSIONS</b>BTX-A is effective for temporary elimination of hyperfunctioning sialorrhea via inhibition of VIP release which plays a key role in modulation of parotid glands secretion.</p>