Development of a rat model of sexual performance anxiety: effect of behavioural and pharmacological hyperadrenergic stimulation on APO-induced erections

Abstract

As part of the multifactorial nature of erectile dysfunction, anxiety associated with sexual performance (SPA) remains a major contributing factor to its progression. In fact, the heightened sympathetic activity associated with sexual performance anxiety may be a key early component of this disruption of normal erectile responses. We are not aware that any animal models have been developed to assess this phenomenon. Using apomorphine (APO, 80 m mg=kg s.c.)-induced erections in rats we characterised the effects of behavioural or pharmacological hyperadrenergic stimulation (that is, anxiety) on erections and hemodynamics. We developed an experimental SPA paradigm by exposing male rats to the stress of being observed by a larger, older male rat placed in close proximity to test rats during APO testing. In a separate group, adrenergic stress was simulated using a sympathomimetic, methoxamine (MXA) given prior to APO testing. In a third group, the changes in circulatory parameters (mean arterial pressure, heart rate) were determined following instrumentation with radiotelemetric transducers for each scenario. APOinduced erections were significantly lower in both the behavioural (1.25 AE 0.8) and pharmacological (0.33 AE 0.5) stressor paradigms compared to controls (2.81 AE 0.9). Further, erections in MXAtreated rats were significantly lower than in the observed scenario. Despite the differences in erections hemodynamic assessments showed no differences in MAP or HR changes between the different experimental conditions. Thus, both the behavioural and pharmacological paradigms of SPA decreased erections, but did not affect the circulation. This suggests that the level of hyperadrenergic input required to induce erectile dysfunction can be subtle, and target only erectogenic pathways.

Mechanisms of Penile Erection and Basis for Pharmacological Treatment of Erectile Dysfunction

“…D 2 receptors in the PVN are believed to be the main site for the induction of erections in the rat (Chen et al, 1999). This may also be the case in man (Brien et al, 2002). Heaton et al (1995) reported that apomorphine, absorbed through the oral mucosa, will act as an erectogenic agent.…”

Pharmacotherapy for Erectile Dysfunction

“…Apomorphine has a higher affinity for the D2‐like receptors [133] that are thought to be the main site for the induction of erections in the PVN [134]. Apomorphine is therefore postulated to increase erectile responses by acting as a conditioner in the PVN, increasing the response to sexual stimuli resulting in enhanced erections induced in the periphery [135].…”

Continuing Medical Education: The Impact of Mental Illness and Psychotropic Medications on Sexual Functioning: The Evidence and Management (CME)

“…In addition, men with SP are more likely to pay for sex, again potentially reflecting anxiety about performance or intimate relatedness. It has been postulated that problems with sexual functioning in patients with SP may be related to behavioral and pharmacologic hyperadrenergic stimulation [17].…”