Biochemical and functional characterization of alpha-adrenergic receptors in the rabbit vagina.
Vascular and non-vascular smooth muscle within the vagina mediate important physiological changes during sexual arousal in women. In this study, we have characterized alpha-adrenergic receptors (AR) in rabbit vagina by assessment of radioligand binding, contractility of isolated tissue strips and genital hemodynamics. [3H]Prazosin and [3H]RX821002 (alpha-1 and alpha-2 AR selective antagonists) bound to rabbit vaginal membrane preparations with high affinity and limited capacity. Competition binding assays using both non-selective and subtype selective ligands for AR (phentolamine, prazosin, delequamine, rauwolscine and UK14304) further confirmed the presence of alpha-1 and alpha-2 AR in vaginal tissue. In organ bath preparations of vaginal tissue strips, norepinephrine-induced contraction was attenuated by alpha-1 and alpha-2 AR antagonists (prazosin, tamsulosin, delequamine and phentolamine). In anesthetized rabbits, intravaginal injection of the alpha-1 AR selective antagonist REC 15/2615 (50 and 100 microg/kg) caused a 2 to 3-fold increase in genital tissue oxyhemoglobin (OHb) concentration. Similar increases in tissue OHb were observed with intravaginal injection of phentolamine (500 microg/kg) or a tri-mixture of vasodilators (PGE1, papaverine, phentolamine). REC 15/2615, phentolamine or the tri-mixture also enhanced the amplitude and/or duration of change in genital tissue OHb after pelvic nerve stimulation. Thus, vaginal tissue expresses functional alpha-1 and alpha-2 AR, which modulate vaginal smooth muscle contractility and genital engorgement.
Kim
Noel N
NN
Department of Urology, School of Medicine, Boston University, 700 Albany St. W607, Boston, MA 02118, USA. nnkim@bu.edu
Min
Kweonsik
K
Huang
Yue-hua
YH
Goldstein
Irwin
I
Traish
Abdulmaged M
AM
D000282:Administration, Intravaginal; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D004359:Drug Therapy, Combination; D005260:Female; D019329:Idazoxan / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008024:Ligands; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D010108:Oxyhemoglobins / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism / Q000494:pharmacology; D011817:Rabbits; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012725:Sexual Behavior / Q000502:physiology*; D014621:Vagina / Q000187:drug effects / Q000378:metabolism*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D008024:Ligands; D010108:Oxyhemoglobins; D011942:Receptors, Adrenergic, alpha; D014665:Vasodilator Agents; C058525:2-methoxyidazoxan; D011224:Prazosin; D019329:Idazoxan