Decrease of vasoactive intestinal polypeptide (VIP) in the penises from impotent men.

Vasoactive intestinal polypeptide (VIP)-containing nerves were depleted in the penises of 28 impotent men. The extent of the decrease in VIP-containing nerves broadly reflected the severity of erectile dysfunction. VIP-immunoreactive nerves were most depleted in those men with complete erectile impotence, irrespective of the aetiology of the dysfunction, whereas in those men in whom some erectile function persisted, loss of VIP-immunoreactive nerves was more variable and less complete. Conventional histology demonstrated only mild changes (muscle atrophy and occasional thickening of blood vessel walls). VIP levels, measured by radioimmunoassay of tissue extracts, were depleted by more than 80% in penises from impotent diabetics (43.4 +/- 9.9 pmol/g wet weight [mean +/- SEM]), when compared with 6 controls (189.9 +/- 45.9 pmol/g). These findings not only support the contention that VIP may be the principal neurotransmitter involved in penile erection, but also suggest that depletion of this powerful vasodilatory peptide may play a key role in the development of penile impotence.