An In Vivo Rat Model to Investigate Female Vaginal Arousal Response

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Abstract
We established a rat model to investigate the female vaginal arousal response and the role of the nitric oxide (NO) pathway on vaginal blood flow in vivo. Vaginal blood flow changes induced by pelvic nerve stimulation (PNS) in female Sprague-Dawley rats were determined by laser Doppler flowmetry. Frequency response data were determined in each animal. In addition, changes in vaginal blood flow were measured after intravenous administration of the NO synthase inhibitor L-NAME (NG-nitro-L-arginine methyl ester) or the phosphodiesterase type 5 inhibitor sildenafil in response to PNS at submaximal frequency. Changes in blood flow were evaluated by comparing the area under the curve of each response. Reproducible frequency dependent increases in vaginal blood flow were observed in response to PNS. Administration of L-NAME (a NO synthase inhibitor) resulted in significant attenuation (25.6% to 18.2% vs control at 30 minutes, p <0.00001) of the PNS induced increase in vaginal blood flow. In contrast, sildenafil administration significantly increased PNS induced vaginal blood flow (166.9% ± 25.8% vs control at 30 minutes, p <0.00001). Our data suggest that the rat is a useful and reliable animal model for investigating the vaginal arousal response. In addition, we used this model to demonstrate the important role of the NO-cyclic guanosine monophosphate pathway in vaginal arousal.