1. ¹Laboratorio de Comportamiento Reproductivo, Escuela de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico
2. ²Departamento de Farmacobiología, Cinvestav, IPN, México, DF, Mexico

Correspondence: M Carro-Juárez, Laboratorio de Comportamiento Reproductivo, Escuela de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Tlaxcala, Col. Centro, CP 90000, AP 484, Tlaxcala, Mexico. E-mail: miguel_carro@hotmail.com

Received 29 October 2004; Revised 6 December 2004; Accepted 9 December 2004; Published online 10 February 2005.

Abstract

A spinal pattern generator controls ejaculation in the male rat. In the present study, the hypothesis that the spinal generator for ejaculation was functional at early postnatal stages was evaluated. To this purpose, the expression of the ejaculatory motor pattern and its pharmacological activation in spinally transected neonatal rats from postnatal day 2 to weaning were investigated. Results revealed the presence of the rhythmic ejaculatory motor pattern in neonatal male rats. As in adult sexually experienced animals, the neonatal ejaculatory motor pattern could be elicited after the application of an ejaculation-like-releasing stimulus. The rhythmic genital motor response of neonates exhibited a gradual maturation that was reflected in its motor parameters until showing the features of the adult response at postnatal day 28. Besides, the ejaculatory motor pattern could be induced by the systemic injection of oxytocin in 7-day-old neonates as well as in adult animals. Present findings provide evidence for the presence of the spinal generator for ejaculation early during postnatal development, suggesting that its organisation is innate.