[Immunohistochemical and morphological investigations of the influence of botulinum toxin type A on the submandibular gland of the rats].

Objective: The morphological changes and the expression of substance P of BTX-A effected on the submandibular gland of the rat were investigated in the study.

Method: A total of 18 female Wistar rats were used. BTX-A was injected at right side submandibular gland. All the animals were sacrificed at the 6th day, 10th day and 30th day after treatment. Using morphological and SABC immunohistochemical methods to observe the changes of cell morphology and the expression of substance P after local applications of BTX-A at different times. The left gland was injected with physiological saline as control.

Result: The morphology of acinar cells and ducts were different after BTX-A injection at observed time points. At the 6th day after BTX-A injection, acinar cells began to atrophy. Especially to the 10th day after treatment, lots of acinar cells and gland ducts showed atrophy. At the 30th day, few atrophic acinar cell was observed which was as same as control side. There were no cellular infiltration and necrosis around the acinar cells and ducts in all groups. Immunohistochemical study revealed that the density of substance P immunoreactive (SP-IR) fibers lowered at the 6th day after BTX-A injection. A marked decrease of SP-IR fibers was shown at the 10th day after BTX-A application. There was significant difference vs control side (P<0.01). However, the expression of SP-IR increased at the 30th day, which was similar to control side.

Conclusion: It has been shown that BTX-A induced temporarily atrophy of acinar cells and ducts in rats submandibular gland and reduced the expression of substance P temporarily. The results suggested that local BTX-A treatment was a selective method to treat the hypersalivation.