Localization of peripheral dopamine D1 and D2 receptors in rat corpus cavernosum

Abstract

Objective To detect and locate anatomically peripheral dopamine D1 and D2 receptors in rat cavernosa, as dopamine is important in sexual drive and penile erection through receptors located in the central nervous system. Materials and methods Corpora cavernosa were obtained from Sprague-Dawley rats; total RNA and membrane proteins were extracted and cryostat sections prepared. The rat brain hypothalamus was used as a control for dopamine D1 and D2 receptors. The presence and expression of peripheral dopamine D1 and D2 receptor mRNAs in rat corpus cavernosa was assessed using reverse transcription and polymerase chain reaction (RT-PCR), and Northern blot hybridization using 32 P-UTP-labelled RNA probes. Concurrently, corresponding proteins from D1 and D2 receptors were assayed and detected by a Western blotting technique. The anatomical location of dopamine D1 and D2 receptor mRNAs in rat penile tissues was identified by in situ hybridization using 35 S-UTP-labelled RNA probes in cryostat sections.Immunohistochemical staining was used to locate peripheral dopamine D1 and D2 receptor proteins in rat corpora cavernosa. Results Dopamine D1 and D2 receptor gene expression was detected in rat corpora cavernosa. In situ hybridization signals for dopamine D1 and D2 receptor mRNAs were localized to corpus cavernosal tissues and dorsal vessels in the rat penis. Western blot analyses showed peripheral dopamine D1 and D2 receptor proteins in rat corpora cavernosa. Immunohistochemically, peripheral dopamine D1 and D2 receptor proteins were detected in dorsal nerves, dorsal vessels and corpus cavernosal smooth muscle of the rat penile tissues. Conclusions Peripheral dopamine D1 and D2 receptors are present in the corpora cavernosa of rats. The functional significance of these receptors and signal transduction pathways in modulating the vascular tone of the penis warrants further investigation.

Novel identification of peripheral dopaminergic D2 receptor in male germ cells

“…In addition to the role of pituitary hormones (mainly FSH and LH), a multitude of cell-cell interactions are also involved in this regulation process, which involves soluble and membrane bound factors produced by both somatic and germ cells of the seminiferous tubule [Skinner, 1991;Mauduit and Benahmed, 1996]. The presence of dopamine receptors in rat testis germ cells may suggest unknown interactions between the nervous and reproductive systems [Hyun et al, 2002]. This opens many new possibilities for future research, such as studying the activation of D2 receptor by dopamine inside the seminiferous tubules.…”

“…In a previous study, dopamine D1 and D2 receptor mRNAs and their corresponding proteins were detected in rat corpus cavernosum [Hyun et al, 2002]. Dopamine and apomorphine (a dopamine agonist) induce penile erection in humans and rats, and a stretching-yawning syndrome in normal rats.…”

“…The peripheral location of dopamine receptors and significant physiological effects of dopaminergic agents on renal, adrenal, and cardiovascular function have been documented [Missale et al, 1998]. The presence of dopamine receptor subtypes outside the CNS has been shown by pharmacological and biochemical techniques [Missale et al, 1998;Hyun et al, 2002]. Dopamine receptors have been identified in kidney, heart, and lymphocytes [Ozono et al, 1996;Barili et al, 1998;Caronti et al, 1998;Missale et al, 1998;Amenta et al, 1999].…”

Light and electron microscopic study on the effect of antischizophrenic drugs on the structure of seminiferous tubules of adult male albino rats

“…However, it has been shown in rats that dopamine receptors are present in germ cells of seminiferous tubules [36,37]. Considering that olanzapine and aripiprazole can bind to these receptors, a direct effect of these drugs on spermatogenesis is possible.…”

Animal models of erectile dysfunction (ED): potential utility of non-human primates as a model of atherosclerosis-induced vascular ED

“…Additionally, rats have been used to determine the potential role of peripheral endothelin receptors, 53 dopamine receptors (D1 and D2), 54,55 serotonin receptors, 56 prostanoid receptors, 57 endocannabinoids, 58 the nitric oxide (NO)/guanylate cyclase pathway 59 --61 and the RhoA/Rho-kinase pathway 62 in the pathophysiology and treatment of ED. The role of ion channels (chloride channels, potassium channels) in modulating erectile function has also been well established in the rat model.…”