Expression of brain-derived neurotrophic factor in rapid ejaculator rats: A further study

Repetitive transcranial magnetic stimulation via the hippocampal brain-derived neurotrophic factor-tyrosine kinase receptor B pathway to affect sexual behavior and neuroplasticity in rapid ejaculation rats

BACKGROUND

Premature ejaculation (PE) is the most prevalent sexual dysfunction among men. Eejaculation involves a complex nervous mechanism in which the ejaculatory centers play a key role in modulating sperm emission. Although treatment possibilities span from psychotherapy to pharmacological approaches, results show inconsistent efficacy. In this context, the emergence of repetitive transcranial magnetic stimulation (rTMS) as a non-invasive neuromodulatory approach represents a compelling avenue for potential therapeutic exploration.

OBJECTIVE

To investigate whether high-frequency transcranial magnetic stimulation can modulate the ejaculatory behavior of rats with rapid ejaculation by altering neurotransmitter levels and neuroplasticity in the hippocampus.

METHODS

Rats have been screened for rapid ejaculation by observing behavioral indices of mating, and subsequently divided into two groups. The intervention group was administered with a 10 Hz rTMS stimulation, whereas the control group received a sham procedure. Upon the delivery of rTMS, we investigated ejaculation latency (EL), the hippocampal 5-hydroxytryptamine (5-HT) concentration, brain-derived neurotrophic factor (BDNF), synaptophysin (SYN), and postsynaptic density protein 95 (PSD95) expressions, as well as BDNF-receptor tyrosine kinase receptor B (TrkB) pathway upregulation.

RESULTS

After 14 days, EL was increased in the intervention group compared with the control group. 5-HT concentration in the hippocampal region was increased, and high-frequency rTMS activated the BDNF and TrkB pathways, including phosphorylation of cAMP response element-binding protein (CREB), and upregulated the transcription and protein expression of SYN, and PSD95.

CONCLUSION

RTMS upregulates BDNF, SYN, and PSD95 expression through activation of the BDNF-TrkB pathway and increases brain 5-hydroxytryptamine thereby regulating neuroplasticity and improving ejaculation.

Peripheral platelet count is a diagnostic marker for predicting the risk of rapid ejaculation: findings from a pilot study in rats

Parameters of peripheral blood cell have been shown as the potential predictors of erectile dysfunction (ED). To investigate the clinical significance of hematological parameters for predicting the risk of rapid ejaculation, we established a rat copulatory model on the basis of ejaculation distribution theory. Blood samples from different ejaculatory groups were collected for peripheral blood cell counts and serum serotonin (5-HT) tests. Meanwhile, the relationship between hematological parameters and ejaculatory behaviors was assessed. Final analysis included 11 rapid ejaculators, 10 normal ejaculators, and 10 sluggish ejaculators whose complete data were available. The platelet (PLT) count in rapid ejaculators was significantly lower than that in normal and sluggish ejaculators, whereas the platelet distribution width (PDW) and mean platelet volume (MPV) were significantly greater in rapid ejaculators. Multivariate logistic regression analysis and receiver operating characteristic (ROC) curve analysis showed that the PLT was an independent protective factor for rapid ejaculation. Meanwhile, rapid ejaculators were found to have the lowest serum 5-HT compared to normal and sluggish ejaculators (P < 0.001). Furthermore, there was a positive correlation between the PLT and serum 5-HT (r = 0.662, P < 0.001), indicating that the PLT could indirectly reflect the serum 5-HT concentration. In addition, we assessed the association between the PLT and ejaculatory parameters. There was a negative correlation between ejaculation frequency (EF) and the PLT (r = -0.595, P < 0.001), whereas there was a positive correlation between ejaculation latency (EL) and the PLT (r = 0.740, P < 0.001). This study indicated that the PLT might be a useful and convenient diagnostic marker for predicting the risk of rapid ejaculation.

Rapid ejaculator rats are more susceptible to anxiety compared with normal ejaculator rats

By observation of Sprague-Dawley male rats with different ejaculatory behaviors, we have identified distinct behavioral characteristics in rapid ejaculator rats. To validate these differential behaviors, we conducted multifaceted behavioral experiments on rapid ejaculator rats and normal rats. Through mating experiments, 42 male rats were categorized into 5 rapid ejaculator rats, 29 normal ejaculator rats, and 8 sluggish ejaculator rats according to their ejaculation frequency. We selected 5 rats exhibiting rapid ejaculation and 5 rats with normal ejaculation for participation in the Morris water maze, open-field test, and balance beam experiments. The open-field tests revealed that rapid ejaculator rats spent shorter time in the center region (1.23 ± 1.21 vs. 6.56 ± 2.40 s, P = 0.0041), less entered the center region (0.80 ± 0.75 vs. 3.40 ± 1.50, time, P = 0.0145), traveled shorter distances (17,003.77 ± 3339.42 vs. 25,037.90 ± 5499.94 mm, P = 0.0371), and had a lower average speed compared with normal rats (66.09 ± 62.36 vs. 195.56 ± 83.41 mm/s, P = 0.0377). However, no significant differences were observed in the Morris water maze and balance beam experiments (0.25 ± 0.05 vs. 0.26 ± 0.07, P = 0.7506;16.40 ± 3.77 vs. 16.25 ± 2.05, P = 0.9515). These behavioral results indicated that the rapid ejaculator rats were more prone to anxiety. To further substantiate this claim, we examined Brain-derived neurotrophic factor expression levels in the hippocampus of rat brains using immunohistochemistry and western blotting. The results demonstrate lower Brain-derived neurotrophic factor expression in the hippocampus of rapid ejaculator rats compared with that in normal rats (P = 0.0093). Thus, our experiments indicate that rapid ejaculator rats exhibit a higher propensity for anxiety, potentially linked to their abnormal neurophysiologic state. It is concluded that rapid ejaculator rats may be more susceptible to anxiety on a pathophysiological basis.

Current and emerging treatment options for premature ejaculation

Premature ejaculation (PE) is a prevalent male sexual dysfunction. Current standard treatment regimens include behavioural therapies, topical anaesthetics, dapoxetine and other selective serotonin reuptake inhibitors (SSRIs). Most of the pharmacotherapeutic options target neurotransmitters (such as serotonin and oxytocin) that have a role in the ejaculation mechanism. However, these treatments are mildly effective and only provide a temporary delay in the ejaculation latency time, and PE recurs when the treatment is stopped. Thus, a treatment for PE is urgently needed and research is ongoing to find the ideal PE therapy. The efficacy and safety of topical anaesthetics and SSRIs in delaying ejaculation have been confirmed in many well-designed controlled trials. Both preclinical and clinical studies on new-generation SSRIs are ongoing. Moreover, promising results came from clinical trials in which the efficacy of on-demand PE therapies targeting neurotransmitters other than serotonin, such as α1-adrenoceptor antagonists and oxytocin antagonists, was assessed. Surgical intervention and neuromodulation have been proposed as potential treatment options for PE; however, current PE guidelines do not recommend these treatments owing to safety concerns.