Metachlorophenylpiperazine (m-CPP) induced intracavernous pressure responses in anaesthetized rats

The supraspinal network in the control of erection

Penile erection is a complex event controlled by vascular, hormonal and neuronal systems. The neuronal system involved in erection is often divided into spinal and supraspinal networks. It is generally accepted that the spinal system directly controls erection and that the supraspinal network modulates this control mechanism through different ascending and descending pathways. In contrast to the spinal control of erection, relatively little is known about the supraspinal network. In the present review, the authors outline the supraspinal network involved in the control of penile erection. Firstly, the brain regions reported to be involved in erection are described and the brain circuit of erection is outlined. Subsequently, the neuromediators involved in erection are summarised. Finally, these data are discussed in the light of therapeutic possibilities in the management of erectile dysfunction by targeting the supraspinal system.

Characterization of intracavernous pressure increase induced by Ym348, a novel 5-HT2C receptor agonist, in anesthetized rats

PURPOSE

We investigated the effects of the novel 5-HT2C receptor agonist YM348 [(S)-2-(7-ethyl-1H-furo[2,3-g]indazol-1-yl)-1-methylethylamine] on ICP in anesthetized rats and clarified whether behavioral changes such as hypolocomotion induced at a high dose are a cause of the inverted U-shaped PE dose-response curves in conscious rats.

MATERIALS AND METHODS

Male Wistar rats (Japan SLC, Shizuoka, Japan) weighing 250 to 315 gm were used. The pro-erectile effect of YM348 (2.03 to 67.7 microg/kg subcutaneously) was examined in conscious rats. ICP was also monitored after YM348 treatment (0.677 to 67.7 mug/kg subcutaneously) in anesthetized rats. Response number, latency, duration, peak pressure and area under the curve were measured. The selective 5-HT2C receptor antagonist SB242084 [(6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy) pyridin-3-yl carbamoyl] indoline)] (0.03 to 1 mg/kg intraperitoneally) was administered 30 minutes before YM348 treatment.

RESULTS

YM348 induced PE and ICP increases, and was significantly inhibited by SB242084. Dose-response curves for the number of PEs and ICP increases were an inverted U shape. YM348 decreased the latency of but did not affect the quality of ICP (duration, peak pressure and area under the curve) even at the highest dose.

CONCLUSIONS

Activation of 5-HT2C receptor increased ICP and, as a result, induced PE. Since the dose-response curve for the number of ICP increases under anesthetized, behavior independent conditions still showed an inverted U shape, behavioral changes were not likely to have contributed to the inverted U-shaped dose-response curves for the number of PEs in conscious rats. Furthermore, the certain magnitude of ICP increases was likely to have occurred despite the stimulus intensity after the level of 5-HT2C receptor activation crossed the threshold.