Abstract
Aim To investigate the possible beneficial effect of mirabegron [a selective β3-adrenoceptor (AR) agonist] treatment on erectile dysfunction (ED) in streptozotocin-induced
diabetic rats.
Methods Sprague-Dawley rats (n=20) were divided into two groups: control group and streptozotocin-induced
diabetic group. In vivo erectile responses were evaluated after intracavernosal injection
of mirabegron (0.4 mg/kg) in rats. The relaxation responses to electrical field stimulation
(EFS, 10 Hz), sodium nitroprusside (SNP, 10 nM) and sildenafil (1 μM) of corpus cavernosum
(CC) strips were examined after the incubation with mirabegron (10 μM). β3-ARs expression and localization were determined by Western blot and immunohistochemical
analyses in CC tissue.
Results In vivo erectile responses of diabetic rats [intracavernasal pressure (ICP) / mean
arterial pressure, 0.17±0.01] were decreased, which were restored after administration
of mirabegron (0.75±0.01, P<0.001). The basal ICP (7.1±0.6 mmHg) in diabetic rats
was markedly increased after mirabegron (36.1 ±5.4 mmHg, P<0.01). Mirabegron caused
markedly relaxation in diabetic rat CC after phenylephrine precontraction. The relaxation
responses to EFS and sildenafil were reduced in diabetic CC, which were increased
in the presence of mirabegron. Mirabegron enhanced SNP-induced relaxation response
in both groups. The expression and immunoreactivity of β3-ARs localized to CC smooth muscle were observed in control and diabetic rats.
Conclusions This is the first study to show that intracavernosal administration of mirabegron
improved erectile function and neurogenic relaxation of CC in diabetic rats. These
results may be supported by further studies using combinations of mirabegron and phosphodiesterase
type 5 (PDE5) inhibitors for the treatment of diabetic ED, especially in patients
who do not respond to PDE5 inhibitor therapy.
Key words
corpus cavernosum - erectile dysfunction - intracavernosal pressure - mirabegron -
diabetes.