Expression and Localization of Peripheral Dopamine D1 and D2 Receptors in Rat and Human Seminal Vesicle

Hyun, Jae Seog; Hellstrom, Wayne J G

Abstract

PURPOSE
Dopamine, an established neurotransmitter in the central nervous system, is recognized for its role in penile erection and ejaculation in rats. However, its complete mechanism of action in the genitourinary tract is unknown. The objective of this study was to investigate the existence and expression of peripheral dopamine D1 and D2 receptor mRNAs and also the corresponding proteins in rat and human seminal vesicles. Concurrently, immunohistochemical staining was carried out for localizing peripheral dopamine D1 and D2 receptor proteins in rat and human seminal vesicles.
MATERIALS AND METHODS
The seminal vesicle tissues of male Sprague-Dawley rats and human radical prostatectomy specimens were used for the extraction of total RNA and proteins, and for the preparation of slide sections. The hypothalamus tissues of rat brain served as a control for dopamine D1 and D2 receptors. The presence and the expression of peripheral dopamine D1 and D2 receptor mRNAs in rat and human seminal vesicle tissues was performed by reverse transcription-polymerase chain reactions (RT-PCR). At the same time the detection of corresponding proteins of D1 and D2 receptor was also investigated by using Western blotting technique. The anatomical localizations of dopamine D1 and D2 receptor proteins in rat and human seminal vesicle were identified by immunohistochemical staining using an antipeptide polyclonal rabbit antibody.
RESULTS
Dopamine D1 and D2 receptor genes expression were detected in both human and rat seminal vesicle tissues. Western blot analyses demonstrated that peripheral dopamine D1 and D2 receptor proteins exist in both human and rat seminal vesicle tissues. Immunohistochemical localization of peripheral dopamine D1 and D2 receptor proteins were demonstrated in smooth muscle layer of human and rat seminal vesicle.
CONCLUSIONS
The results of this study demonstrate that peripheral dopamine D1 and D2 receptors are present in the seminal vesicle tissue of both rats and humans. These results suggest that seminal emission may be mediated in part by stimulation of peripheral dopamine receptors located in the seminal vesicles.