Pharmacological Studies on the Role of 5-HT1 A Receptors in Male Sexual Behavior of Wildtype and Serotonin Transporter Knockout Rats

Brain serotonin (5-HT) neurotransmission plays an important role in male sexual behavior and it is well established that activating 5-HT_{1 A} receptors in rats facilitate ejaculatory behavior. However, the relative contribution of 5-HT_{1 A} somatodendritic autoreceptors and heteroreceptors in this pro-sexual behavior is unclear. Moreover, it is unclear whether the contribution of somatodendritic 5-HT_{1 A} autoreceptors and postsynaptic 5-HT_{1 A} heteroreceptors alter when extracellular 5-HT levels are chronically increased. Serotonin transporter knockout (SERT^-/-) rats exhibit enhanced extracellular 5-HT levels and desensitized 5-HT_{1 A} receptors. These rats model neurochemical changes underlying chronic SSRI-induced sexual dysfunction. We want to determine the role of presynaptic versus postsynaptic 5-HT_{1 A} receptors in the pro-sexual effects of 5-HT_{1 A} receptor agonists in SERT^+/+ and in SERT^-/- rats. Therefore, acute effects of the biased 5-HT_{1 A} receptor agonists F-13714, a preferential 5-HT_{1 A} autoreceptor agonist, or F-15599, a preferential 5-HT_{1 A} heteroreceptor agonist, and S15535 a mixed 5-HT_{1 A} autoreceptor agonist/heteroreceptor antagonist, on male sexual behavior were assessed. A clear and stable genotype effect was found after training where SERT^+/+ performed sexual behavior at a higher level than SERT^-/- rats. Both F-15599 and F-13714 induced pro-sexual activity in SERT^+/+ and SERT^-/- animals. Compared to SERT^+/+, the F13714-dose-response curve in SERT^-/- rats was shifted to the right. SERT^+/+ and SERT^-/- rats responded similar to F15599. Within both SERT^+/+ and SERT^-/- rats the potency of F-13714 was much stronger compared to F-15599. S15535 had no effect on sexual behavior in either genotype. In SERT^+/+ and SERT^-/- rats that were selected on comparable low sexual activity (SERT^+/+ 3 or less ejaculations and SERT^-/- 5 or less ejaculations in 10 weeks) S15535 also did not influence sexual behavior. The two biased compounds with differential effects on 5-HT_{1 A} auto- and hetero-receptors, exerted pro-sexual activity in both SERT^+/+ and SERT^-/- rats. Applying these specific pharmacological tools has not solved whether pre- or post-synaptic 5-HT_{1 A} receptors are involved in pro-sexual activity. Moreover, the inactivity of S15535 in male sexual behavior in either genotype was unexpected. The question is whether the in vivo pharmacological profile of the different 5-HT_{1 A} receptor ligands used, is sufficient to differentiate pre- and/or post-synaptic 5-HT_{1 A} receptor contributions in male rat sexual behavior.

[Practice guideline 'Premature ejaculation']

In 2010 the International Society of Sexual Medicine published its practice guideline for the diagnosis and treatment of premature ejaculation. This guideline was translated and adapted on a number of points by a committee consisting of members of two Dutch sexological societies, the 'WVSD' and the 'NVVS'. The most important subjects in this guideline are: (a) the case history is the most important diagnostic tool; (b) a physical examination is usually not necessary; (c) determination of the subtype of premature ejaculation can guide treatment; (d) pharmacotherapy alone is only applicable for primary premature ejaculation; (e) combination therapy is preferable for the secondary form of premature ejaculation, and pharmacotherapy is contraindicated for the other 2 subtypes.

Serotonin transporter null mutation and sexual behavior in female rats: 5-HT1A receptor desensitization

INTRODUCTION

Serotonin plays a key role in sexual behavior. In serotonin transporter (SERT) knockout rats (-/-), basal extracellular 5-HT levels are considerably increased, indicating a serotonergic disturbance. Heterozygous SERT(+/-) rats express 50% of SERT in comparison to wild-type rats and may therefore model the s/s phenotype of the human SERT promoter (5-HTTLPR) polymorphism.

AIM

In the present study, we used both homozygote and heterozygote SERT knockout and wild-type rats (+/+) to study the putative role of the SERT in female sexual behavior.

METHODS

Female rats were brought into estrous by hormonal injections before a paced mating sex test. The effects of the 5-HT(1A)/5-HT(7) receptor agonist (+/-)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (+/-8-OH-DPAT) (0.03-1 mg/kg s.c.) and the 5-HT(1A) receptor antagonist WAY-100635 (0.1-1-mg/kg i.p.) on sexual behaviors of the females were tested separately and in a selected combination of both in all three genotypes.

MAIN OUTCOME MEASURES

Proceptive (darting and hopping) and receptive (lordosis) behaviors were quantified.

RESULTS

Basal proceptive and receptive sexual activities were not different between SERT+/+, +/- and -/- female rats. The dose-effect curve after +/-8-OH-DPAT for these activities was clearly shifted to the right in SERT-/- animals compared to other genotypes. WAY-100635 alone had no effect on sexual behavior in any genotype, but was able to antagonize the +/-8-OH-DPAT-induced decrease in sexual activities indicating the involvement of the 5-HT(1A) receptor.

CONCLUSIONS

The absence (-/-) or reduced (+/-) expression of SERT does not affect basal sexual activity in female rats in a paced mating situation. The data indicate a desensitized 5-HT1A receptor in the SERT-/-, but not in the SERT+/- females. Under normal basal conditions, desensitized 5-HT1A receptors apparently do not play a role in female sexual behavior of the SERT-/-. However, upon activation of the 5-HT1A receptor in "normal" females (SERT+/+ and SERT+/-), a hyposexual behavior is induced.

Topical eutectic mixture for premature ejaculation (TEMPE): a novel aerosol-delivery form of lidocaine-prilocaine for treating premature ejaculation

OBJECTIVE

To evaluate, in a phase II study, the efficacy and safety of a topical eutectic mixture for premature ejaculation (TEMPE), a metered-dose aerosol spray containing a eutectic mixture of lidocaine and prilocaine, as a treatment for PE.

PATIENTS AND METHODS

Men with PE (Diagnostic and Statistical Manual-IV definition) aged 18-75 years were randomized into a double-blind, placebo-controlled study in the UK and the Netherlands. Efficacy variables included the mean change in intravaginal ejaculatory latency time (IELT) from baseline and the proportion of patients who achieved an IELT of > or = 4, > or = 3 or > or = 2 min on two occasions, and the effect of TEMPE on the index of ejaculatory control (IEC) and sexual quality-of-life (SQoL) scores of patients and their partners. Safety and adverse event data were also collected. Fifty-four patients were randomized and received study treatment.

RESULTS

The observed mean change in IELT from baseline to the end of the treatment period was 3.8 min in the TEMPE group and 0.7 min in the placebo group, and when adjusted for baseline and centre was 2.4 times higher in the TEMPE than the placebo group (P < 0.01). The efficacy of TEMPE in increasing IELT was further supported by positive trends in the other efficacy endpoints. The proportion of men who had an IELT time > or = 2, > or = 3 or > or = 4 min on two occasions after treatment was 11/20 (55%), 8/20 (40%) and 5/25 (20%) in the TEMPE group, and 8/23 (35%), 3/23 (13%) and 3/23 (13%) in the placebo group, respectively, although these differences were not statistically significant. Improvements in IEC and SQoL (male and female) scores also showed trends towards greater efficacy for TEMPE than placebo. In all, 35 of 42 (83%) patients considered the spray easy to use. Mild to moderate local numbness occurred in three (12%) of the TEMPE-treated patients but did not lead to discontinuation.

CONCLUSION

Topical treatment with TEMPE produced a statistically and clinically significant increase in IELT compared with placebo, and resulted in positive trends in ejaculatory control and SQoL. TEMPE was considered easy to use and was well tolerated. The data support the conduct of further large-scale studies to establish the utility of TEMPE as a first-line treatment for PE.

Disorders of orgasm and ejaculation in men

INTRODUCTION

Ejaculatory/orgasmic disorders, common male sexual dysfunctions, include premature ejaculation, inhibited ejaculation, anejaculation, retrograde ejaculation and anorgasmia.

AIM

To provide recommendations/guidelines concerning state-of-the-art knowledge for management of ejaculation/orgasmic disorders in men.

METHODS

An International Consultation in collaboration with the major urology and sexual medicine associations assembled over 200 multidisciplinary experts from 60 countries into 17 committees. Committee members established specific objectives and scopes for various male and female sexual medicine topics. The recommendations concerning state-of-the-art knowledge in the respective sexual medicine topic represent the opinion of experts from five continents developed in a process over a 2-year period. Concerning the Disorders of Ejaculation/Orgasm in Men Committee, there were nine experts from six countries.

MAIN OUTCOME MEASURE

Expert opinion was based on grading of evidence-based medical literature, widespread internal committee discussion, public presentation and debate.

RESULTS

Premature ejaculation management is dependent upon etiology. When secondary to ED, etiology-specific treatment is employed. When lifelong, initial pharmacotherapy (SSRI, topical anesthesia, PDE5 inhibitors) is appropriate. When associated with psychogenic/relationship factors, behavioral therapy is indicated. When acquired, pharmacotherapy and/or behavioral therapies are preferred. Retrograde ejaculation, diagnosed with spermatozoa and fructose in centrifuged post-ejaculatory voided urine, is managed by education, patient reassurance, pharmacotherapy or bladder neck reconstruction. Men with anejaculation or anorgasmia have a biologic failure of emission and/or psychogenic inhibited ejaculation. Men with age-related penile hypoanesthesia should be educated, reassured and be instructed in revised sexual techniques which maximize arousal.

CONCLUSIONS

More research is needed in understanding management of men with ejaculation/orgasmic dysfunction.