H. Aoki et al., INVOLVEMENT OF VASOACTIVE-INTESTINAL-PEPTIDE (VIP) AS A HUMORAL MEDIATOR OF PENILE ERECTILE FUNCTION IN THE DOG, Journal of andrology, 15(2), 1994, pp. 174-182
The effects of intracorporeal infusion of anti-vasoactive intestinal p
eptide (anti-VIP) antisera on electrically induced penile erection wer
e studied in 18 male mongrel dogs. Electrical pulse stimulation (4 V,
4 milliseconds, 40 Hz) of the pelvic splanchnic nerve consistently pro
duced penile erection (''electroerection''). Using this erection model
, effects of anti-VIP serum were evaluated with regard to the peak int
racorporeal pressure during electroerection. Pretreatment of the anima
ls with repetitive intracorporeal infusion of anti-VIP rabbit serum co
mpletely abolished the electroerection in nine dogs, partially suppres
sed it (P < 0.01) in five, and was without effects in four. In contras
t, control treatment of the same 18 dogs with normal rabbit serum was
totally ineffective. In six dogs in which anti-VIP serum failed to pro
duce a complete suppression of electroerection, 0.5 mg atropine sulfat
e was additionally given i.v. All six dogs exhibited significant (P <
0.01) suppression of the peak intracorporeal pressure after atropine.
However atropine alone did not affect the intracorporeal pressure to a
ny significant degree. To five of these six dogs with positive respons
e to the combination treatment with anti-VIP serum and atropine, prazo
sin HCl was added i.v. It was found that prazosin HCl reversed the att
enuation of electroerection produced by combined anti-VIP serum and at
ropine. Prazosin did not affect the intracorporeal pressure when admin
istered following anti-VIP serum. These results suggest that VIP plays
a role as a humoral mediator involved in penile erection and that the
re is a synergistic interaction between VIP and acetylcholine. Also it
appears that the effect of acetylcholine but not that of VIP is media
ted by the alpha-1 adrenergic mechanism.