Down-regulation of Dopamine D1 Receptor in Rat Penile Tissue after Cavernous Neurotomy

Hyun, Jae Seog; Jung, Hang Ki; Bahk, Jong Yoon

Abstract

PURPOSE: Dopamine plays a critical role in promoting sexual drive and penile erection through dopamine receptors. This study was performed to investigate whether the cavernousal nerve controls the expression of peripheral dopamine D1 receptors in rat penile tissues after cavernousal nerve injury.
MATERIALS AND METHODS
Male rats (n=20) were divided into two groups: a control group consisting of sham-operated rats (n=10) and an experimental group consisting of rats that underwent incision of the bilateral cavernous nerve (n=10). Three months later, the intracavernous pressure response was monitored using an intracavernous papaverine injection of 300 microgram. The expression of dopamine D1 receptor mRNA were studied using an RT-PCR method, and dopamine D1 receptor protein expression by Western blot analysis and immuno-histochemical staining in each group. The expressed band density of the RT-PCR and Western blot were measured by a densitometer.
RESULTS
Erectile functions, as studied by intracavernosal papaverine injection at three months, were similar in both groups. The dopamine D1 receptor mRNA and protein expressions were significantly lower in the neurotomy group. The immuno-histochemical staining also showed a reduction in the dopamine D1 receptor expression in the neurotomy group compared with the control group.
CONCLUSIONS
Our results show that dopamine D1 receptors in penile tissues were down-regulated following cavernousal nerve injury. These findings suggest that cavernousal nerve injury affects directly the reduction of dopamine D1 receptor expression, and that the action of dopamine on the cavernousal dopamine receptor will be affected in cavernousal nerve injured rats.