Effect of a gel containing pilocarpine on vaginal atrophy in castrated rats

Abstract

Objectives: To evaluate the effect of Carbopol gel formulations containing pilocarpine on the morphology and morphometry of the vaginal epithelium of castrated rats.

Methods: Thirty-one female Wistar-Hannover rats were randomly divided into four groups: the control Groups I (n=7, rats in persistent estrus; positive controls) and II (n=7, castrated rats, negative controls) and the experimental Groups, III (n=8) and IV (n=9). Persistent estrus (Group I) was achieved with a subcutaneous injection of testosterone propionate on the second postnatal day. At 90 days postnatal, rats in Groups II, III and IV were castrated and treated vaginally for 14 days with Carbopol gel (vehicle alone) or Carbopol gel containing 5% and 15% pilocarpine, respectively. Next, all of the animals were euthanized and their vaginas were removed for histological evaluation. A non-parametric test with a weighted linear regression model was used for data analysis (p<0.05).

Results: The morphological evaluation showed maturation of the vaginal epithelium with keratinization in Group I, whereas signs of vaginal atrophy were present in the rats of the other groups. Morphometric examinations showed mean thickness values of the vaginal epithelium of 195.10±12.23 μm, 30.90±1.14 μm, 28.16±2.98 μm and 29.84±2.30 μm in Groups I, II, III and IV, respectively, with statistically significant differences between Group I and the other three groups (p<0.0001) and no differences between Groups II, III and IV (p=0.0809).

Conclusion: Topical gel formulations containing pilocarpine had no effect on atrophy of the vaginal epithelium in the castrated female rats.

Figure 1

Photomicrographs of histological sections of the vaginal epithelium of rats. Note the thickness of the vaginal epithelium (E) and keratin in rats in persistent estrus (A) and the thin layer of basal and parabasal cells in the castrated rats of Groups II (vehicle) (B), III (5% pilocarpine) (C) and IV (15% pilocarpine) (D). Original magnification 100x.