Study Of Dependence Of Protein Expression Of Calcitonin Gene Related Peptide Onandrogen In Rat Penis

Although androgens are essential for expression of normal libido in male, their role in the maintenance of the processes of penile erection is much less clear. Many researches indicated that nitric oxide (NO)> vasoactive intestinal polypeptide (VIP) , calcitonin gene-related peptide (CGRP) ^ substance P are main neurotransmitters for penile erection. Although some studies have revealed the dependence of mRAN expression of nitric oxide synthase (NOS) and VIP on androgen in rat penis, so far no study has investigated whether protein expression of CGRP in rat penis is regulated by androgen, including testosterone (T) and dihydrotestosterone (DHT), or whether CGRP is dependent on T or DHT. In this research, on the basis of our animal models, the effect of androgen on protein expression of CGRP of SD rats was studied. Objective:In order to know the dependence of protein expression of CGRP on androgens (testosterone and dihydrotestosterone ). Whether androgens could affect the protein expressions of CGRP in rat penis.Materials and Methods:The study was conducted on 64 male Sprague-Dawley (SD) rats (10 weeks old, body weight 320?2g). Rats were maintained in alternating cycles of darkness (6:00 p.m. to 6:00 a.m.) and light 6:00 a.m. to 6:00 p.m.). Food and water were freely available. Rats were randomly divided into 4 groups: GroupA. castrated: Group B. treated with finasteride 4.5mg/kg/day. orally; Group C. castrated, treated with testosterone undecanoate 50mg/kg/month. intramuscular injection and Group D. intact control. Four and ten weeks after treatments described above, half of rats were killed under the condition of intraperitoneal injection of ketamine (35mg/kg). During the operation, blood samples were taken for the measurements of testosterone (T) and dihydrotestosterone (DHT) by radioimmunoassay. Penis samples were stored under 10% formaldehyde (for the second part of the research). Paraffin-embedded tissue sections of the rat penis were stained with antibodies against CGRP using Envision System immunohistochemical technique. Those nerve fibers whose colors were stained to be brown-yellow were identified to be CGRP positive nerve fibers. At *200 magnification of light microscopy, computer assisted quantitative image analysis system was used to count the mean areas of CGRP positive nerve fibers and CGRP negative nerve fibers of 5 randomly selected fields of each section, so as to count the percent of CGRP positive nerve fibers area.SPSS 10.0 statistical computer programs were used, if PO.05. it means that difference between two groups is significant.Results:1. There was no significant difference of the percent of CGRP positive nerve fibers area between group A. B. C and group D in 4 weeks model (P=0.276. 0.068,0.176)2. In 10 weeks model, the percent of CGRP positive nerve fibers area of control group was significant higher than that of group A, group B, group C (E=0.000,.0.000, 0.000)3. In each experimental group, the percent of CGRP positive nerve fibers area in each 4 weeks model was significant higher than that of 10 weeks model (P=0.013, 0.031, 0.000); while in control group, there was no significant difference of the percent of CGRP positive nerve fibers area between 4 and 10 weeks models (P=0.579).Conclusions:1 . The serum level of androgens may have an effect on the protein expression of CGRP of the rat penile nervous tissue. Decrease of the serum level of androgen results in the lower expression of CGRP; and with the time passing, it becomes more distinct.2. Androgens may give rise to the penile erection via CGRP.