title: Vasoactive intestinal polypeptide, an erectile neurotransmitter, improves erectile function more significantly in castrated rats than in normal rats.
abstract: OBJECTIVE
  • To investigate the regulatory role of androgen in VIP-mediated erectile effect. Androgen is essential for physiological erection. Vasoactive intestinal polypeptide (VIP) is an important erectile neurotransmitter. While previous studies demonstrated that VIP expression in the penis was androgen-independent, it remains controversial whether androgen has any effect on VIP-mediated erection.
  
  
  METHODS
  • Male SD rats were divided into a control group, a castration group, and a castration-with-testosterone-replacement group. Four weeks later, each group was subdivided into low and high-dose VIP subgroups and subjected to intracavernous injection of 0.5 and 2 µg VIP, respectively. • Erectile function was tested by recording intracavernosal pressure (ICP) and mean arterial blood pressure (MAP) before and after VIP injection. • The expressions of the VIP-receptor (VPAC2), G-protein stimulatory and inhibitory alpha subunits (Gs-α, Gi-α), and PDE3A in rat corpus cavernosum (CC) was qualified by real-time PCR and Western blot analysis.
  
  
  RESULTS
  • Castration reduced erectile function while testosterone restored it. VIP improved erectile function in a dose-dependent manner. • High-dose VIP significantly enhanced erectile function in castrated rats and there was no difference of ICP/MAP among three groups after injection of high-dose VIP. • Low-dose VIP also resulted in a higher improvement of erectile function in castrated rats, although the ICP/MAP was lower in these rats than in the other two groups. VPAC2 and Gs-α were up-regulated while Gi-α and PDE3A were down-regulated in CC of castrated rats.
  
  
  CONCLUSIONS
  • VIP improves erectile function much more significantly in hypogonadal condition, mainly due to the higher expression of VPAC2, Gs-α, and lower expression of Gi-α and PDE3A in CC of castrated rats. Androgen may negatively regulate the erectile effect of VIP.
authors.affiliation: Department of Urology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, PR China. zhangmg1970@hotmail.com
authors.forename: Min-Guang
authors.initials: MG
authors.lastname: Zhang
authors.forename: Zhou-Jun
authors.initials: ZJ
authors.lastname: Shen
authors.forename: Cun-Ming
authors.initials: CM
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Ping-Jin
authors.initials: PJ
authors.lastname: Gao
authors.forename: Shan-Wen
authors.initials: SW
authors.lastname: Chen
authors.forename: Wen-Long
authors.initials: WL
authors.lastname: Zhou
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D007267:Injections; D008297:Male; D018377:Neurotransmitter Agents / Q000008:administration & dosage / Q000494:pharmacology*; D009919:Orchiectomy; D010410:Penile Erection / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D014660:Vasoactive Intestinal Peptide / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D018377:Neurotransmitter Agents; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D014660:Vasoactive Intestinal Peptide; D013739:Testosterone; D019205:GTP-Binding Protein alpha Subunits, Gs