A role for ATP-sensitive potassium channels in male sexual behavior

Carbamazepine-induced sperm disorders can be associated with the altered expressions of testicular KCNJ11/miR-let-7a and spermatozoal CFTR/miR-27a

Male infertility is a global health problem, and the underlying molecular mechanisms are not clearly known. Ion channels and microRNAs (miRNAs), known to function in many vital functions in cells, have been shown to play a significant role in male infertility through changes in their expressions. The study aimed to evaluate the alterations of testicular and/or spermatozoal potassium voltage-gated channel subfamily J member 11 (KCNJ11), Cystic fibrosis transmembrane conductance regulator (CFTR), miR-let-7a and miR-27a expressions in carbamazepine-related male infertility. Here, we showed that carbamazepine reduced sperm motility, increased abnormal sperm morphology, and impaired hormonal balance as well as increased relative testis weight and decreased relative seminal vesicle weight. On the other hand, downregulated KCNJ11 and upregulated miR-let-7a expressions were determined in testis (p < .05). Also, downregulated KCNJ11 and upregulated CFTR and miR-27a expressions were found in spermatozoa (p < .05). Interestingly, altered testicular KCNJ11 and miR-let-7a expressions were correlated with decreased sperm motility and elevated sperm tail defect. Besides, spermatozoal CFTR and miR-27a expressions positively correlated with sperm tail defects. The results indicated a significant relationship between ion channel and/or miRNA expression alterations and impaired sperm parameters due to carbamazepine usage.

Verapamil-induced ion channel and miRNA expression changes in rat testis and/or spermatozoa may be associated with male infertility

The effect of verapamil, a calcium channel blocker, on male fertility in terms of ion channel and miRNA gene expressions in testis/spermatozoa was evaluated in this study. Rats were divided into sham and verapamil groups (n = 15). Verapamil was performed orally for 60 days. Sperm parameters and levels of serum follicle-stimulating hormone (FSH), luteinising hormone (LH) and testosterone (T) hormones were analysed. Alterations of microRNA (miRNA) and ion channel gene expressions in spermatozoa/testis were detected by using qPCR. Verapamil treatment reduced sperm concentration. Increased serum FSH, LH and T hormone levels were detected. Upregulated transient receptor potential cation channel subfamily V member 5 (TRPV5) and potassium voltage-gated channel subfamily J member 11 (KCNJ11) gene expressions and downregulated miR-let-7b, miR-10a, miR-320 and miR-760 expressions were found in testis of verapamil group. However, upregulated anoctamin 1 (ANO1), ATP-binding cassette subfamily C member 9 (ABCC9), miR-27a and miR-130a expressions and downregulated miR-20a, miR-92a, miR-132, miR-320 and miR-760 expressions were detected in spermatozoa. In addition, these altered gene expressions were found to be associated with decreased sperm concentration. The results indicate that the changes in testicular and/or spermatozoal ion channels and miRNA expressions due to verapamil treatment may affect male fertility.

Androgen Affects the Dynamics of Intrinsic Plasticity of Pyramidal Neurons in the CA1 Hippocampal Subfield in Adolescent Male Rats

Androgen receptor (AR) is abundantly expressed in the preoptico-hypothalamic area, bed nucleus of stria terminalis, and medial amygdala of the brain where androgen plays an important role in regulating male sociosexual, emotional and aggressive behaviors. In addition to these brain regions, AR is also highly expressed in the hippocampus, suggesting that the hippocampus is another major target of androgenic modulation. It is known that androgen can modulate synaptic plasticity in the CA1 hippocampal subfield. However, to date, the effects of androgen on the intrinsic plasticity of hippocampal neurons have not been clearly elucidated. In this study, the effects of androgen on the expression of AR in the hippocampus and on the dynamics of intrinsic plasticity of CA1 pyramidal neurons were examined using immunohistochemistry, Western blotting and whole-cell current-clamp recording in unoperated, sham-operated, orchiectomized (OCX), OCX + testosterone (T) or OCX + dihydrotestosterone (DHT)-primed adolescent male rats. Orchiectomy significantly decreased AR-immunoreactivity, resting membrane potential, action potential numbers, afterhyperpolarization amplitude and membrane resistance, whereas it significantly increased action potential threshold and membrane capacitance. These effects were successfully reversed by treatment with either aromatizable androgen T or non-aromatizable androgen DHT. Furthermore, administration of the AR-antagonist flutamide in intact rats showed similar changes to those in OCX rats, suggesting that androgens affect the excitability of CA1 pyramidal neurons possibly by acting on the AR. Our current study potentially clarifies the role of androgen in enhancing the basal excitability of the CA1 pyramidal neurons, which may influence selective neuronal excitation/activation to modulate certain hippocampal functions.

Possible involvement of monoamine neurons in the emotional abnormality in Kir6.2-deficient mice

ATP-sensitive potassium (K_ATP) channels consist of two structurally different subunits: a pore-forming subunit of the Kir6.0-family (Kir6.1 or Kir6.2) and a regulatory sulfonylurea receptor subunit (SUR1, SUR2A or SUR2B). Although Kir6.2 is widely distributed in the brain, the mechanisms that underlie the impact of Kir6.2 on emotional behavior are not yet fully understood. To clarify the role of Kir6.2 in emotional behavior, in the present study, we investigated the behavioral characteristics of Kir6.2-knockout (Kir6.2^-/-) mice. Kir6.2^-/- mice showed impaired general behavior in a locomotor activity test and open field test. In addition, anxiety-like behavior was observed in the open field test, elevated plus-maze test and light-dark test. In particular, excessive anxiety-like behavior was observed in female Kir6.2^-/- mice. Moreover, we investigated whether Kir6.2 is expressed on monoamine neurons in the brain. Immunohistochemical studies showed that Kir6.2 was co-localized with tryptophan hydroxylase (TPH), a marker of serotonergic neurons, in dorsal raphe nuclei. Kir6.2 was also co-localized with tyrosine hydroxylase (TH), a marker of dopaminergic/noradrenergic neurons, in the ventral tegmental area and locus coeruleus. Next, we checked the protein levels of TH and TPH in the midbrain. Interestingly, TPH expression was significantly elevated in female Kir6.2^-/- mice. These results suggest that Kir6.2 in monoamine neurons, especially serotonergic neurons, could play a key role in emotional behavior.

Molecular biology of K(ATP) channels and implications for health and disease

The ATP-sensitive potassium (K(ATP)) channel is expressed in most excitable tissues and plays a critical role in numerous physiological processes by coupling intracellular energetics to electrical activity. The channel is comprised of four Kir6.x subunits associated with four regulatory sulfonylurea receptors (SUR). Intracellular ATP acts on Kir6.x to inhibit channel activity, while MgADP stimulates channel activity through SUR. Changes in the cytosolic [ATP] to [ADP] ratio thus determine channel activity. Multiple mutations in Kir6.x and SUR genes have implicated K(ATP) channels in various diseases ranging from diabetes and hyperinsulinism to cardiac arrhythmias and cardiovascular disease. Continuing studies of channel physiology and pathology will bring new insights to the molecular basis of K(ATP) channel function, leading to a better understanding of the role that K(ATP) channels play in both health and disease.

Ginsenoside Rg1 improves male copulatory behavior via nitric oxide/cyclic guanosine monophosphate pathway

INTRODUCTION

Ginsenoside Rg1 is the purified ingredient from ginseng, there has been little research on the effect of Rg1 on male copulatory behavior and its mechanism of action.

AIM

The purpose of this study was to investigate the effect of ginsenoside Rg1 on copulatory behavior of male mice and the mechanism of its action.

METHODS

Male mice were treated with Rg1 intraperitoneally; three elements of copulatory behavior (mounting, intromission, pelvic thrusting) were assessed. After final treatment and behavior determination, nitric oxide (NO) concentration were determined by spectrophotometry method. Plasma testosterone, cyclic guanosine monophosphate (cGMP) in corpus cavernosum both in vivo and in vitro were measured by radioimmunoassay. Rabbit corpus cavernosum segments were incubated with Rg1 (0.05, 0.5 and 5 microM) in the presence of exogenous NO donor sodium nitroprusside (SNP) (10 microM), and the cGMP level was measured. The half maximal inhibitory concentration (IC50) of Rg1 for phosphodiesterase type 5 (PDE5) inhibitors was determined by measuring the conversion of cGMP to 5'-mononucleotides. Sildenafil was set as a positive control. MAIN COME OUT MEASURES: Mounting and intromission frequency, pelvic thrusts, serum testosterone, NO level, cGMP accumulation, IC50 for PDE5.

RESULTS

Rg1 (10 mg/kg) significantly increased mounting and pelvic thrusting frequency and numbers of intromission of male mice from d16 to d20. Rg1 increased serum testosterone concentration, enhanced NO release, and cGMP accumulation in corpus cavernosum both in vivo and in vitro. The IC50 of sildenafil and Rg1 for PDE5 were 4.24 +/- 0.78 and 12.47 +/- 2.31 nmol/L.

CONCLUSIONS

Ginsenoside Rg1 improved copulatory behavior of male mice and this may attribute to its actions at both testosterone level and signal transduction pathway in corpus cavernosum. NO/cGMP pathway appeared to play a key role in mediating the effect of Rg1 on male sexual function. These experimental data provide evidence that Rg1 could be a promising new drug for erectile dysfunction and low libido.