Elsevier

Neuroscience

Volume 92, Issue 4, June 1999, Pages 1523-1537
Neuroscience

5-Hydroxytryptamine2C receptors on spinal neurons controlling penile erection in the rat

https://doi.org/10.1016/S0306-4522(99)00082-2Get rights and content

Abstract

The localization of 5-hydroxytryptamine2C receptors in the lumbosacral spinal cord of the rat was investigated using selective antibodies raised against the carboxyl-terminal part of the rat receptor. The distribution of immunoperoxidase labelling at the light microscope level revealed numerous labelled neurons in the gray matter, with a higher intensity in the sacral parasympathetic nucleus, the dorsal gray commissure and particularly the motoneurons of the ventral horn. Confocal microscope analysis showed that immunostaining was mainly intracellular (motoneurons), but could also be associated with the membrane of cell bodies and dendrites. Actually, electron microscope immunogold experiments demonstrated an exclusive staining of the cis-Golgi apparatus. Following pseudo-rabies virus transsynaptic retrograde labelling from the corpus cavernosum, labelled neurons were found in the sacral parasympathetic nucleus and the dorsal gray commissure of the L6–S1 segments. All virus-labelled neurons exhibited 5-hydroxytryptamine2C receptor immunoreactivity. These results indicate that all parasympathetic preganglionic neurons and their related interneurons which contribute to the innervation of cavernosal tissue bear 5-hydroxytryptamine2C receptors. In the sacral parasympathetic nucleus, most neurons which were retrogradely-labelled from the pelvic ganglion with Fast Blue also showed 5-hydroxytryptamine2C receptor immunoreactivity. In the ventral horn, motoneurons retrogradely labelled from the ischiocavernosus muscle and the bulbospongiosus muscle, both of which are involved in erection and ejaculation, were also 5-hydroxytryptamine2C receptor-immunopositive.

The supraspinal serotoninergic control of erection at the lumbosacral level therefore appears to be strongly associated with the activation of 5-hydroxytryptamine2C receptors, consistent with the proerectile properties of 5-hydroxytryptamine2C agonists.

Section snippets

Animals and tissue preparation

Adult male Sprague–Dawley rats weighing 250–300 g (Centre d'Elevage Janvier, France) were maintained under standard conditions (22–24°C: 12/12 h light/dark cycle, food and water ad libitum). All efforts were made to minimize animal suffering and to reduce the number of animals used.

Rats were anaesthetized with pentobarbital (50 mg/kg, i.p.) and perfused via the ascending aorta (flow rate 20 ml/min) with 100–150 ml of 0.9% (w/v) NaCl containing sodium nitrite (1 g/l), followed by 650 ml of 4%

Distribution of 5-hydroxytryptamine2C receptor immunoperoxidase labelling at the L5–S1 levels of the spinal cord

At low magnification, the distribution of 5-HT2C receptor immunoreactivity revealed by the ABC method using DAB as a chromogen was homogeneously distributed within the gray matter of the L5–S1 segments of the spinal cord (Fig. 1). The overall distribution was similar at all levels of the spinal cord (not shown). However, slight differences were noticed in the different areas of gray matter at the lumbosacral level. A more intense labelling was found in the intermediolateral column of the L6 and

Evidence for 5-hydroxytryptamine2C receptors in the rat L5–S1 spinal cord

The localization of 5-HT2C receptors in the lumbosacral spinal cord has been described using anti-peptide antibodies directed against the carboxy-terminal part of the rat receptor. These antibodies have been previously characterized in detail and their specificity assessed using Western blotting experiments and cell transfection studies.2 The distribution of 5-HT2C receptor immunoreactivity in the spinal cord closely matched that of 5-HT2A–2C binding sites labelled by [125

Conclusion

The distribution of 5-HT2C receptor immunoreactivity in the lumbosacral spinal cord of the rat was consistent with that of the corresponding mRNA and binding sites.30., 43. Numerous neurons were intracellularly labelled, at the level of the Golgi apparatus, particularly in the SPN and the DGC. The immunocytochemical detection of 5-HT2C receptors combined with pseudo-rabies virus transsynaptic retrograde transport demonstrated that neurons in the SPN and the DGC contributing to the innervation

Acknowledgements

This work was supported by the “Centre National de la Recherche Scientifique” (CNRS) and the “Ministère de l'Education nationale, de la Recherche et de la Technologie”. We thank the Institut Jacques Monod and the CHU Saint-Louis for providing confocal laser scanning microscope facilities. Ms M.-J. Brisorgueil is gratefully acknowledged for expert technical assistance, and V. Setola for reading the manuscript.

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