Blockade of the preovulatory release of gonadotropins and prolactin by spinal transections in female rats.

Abstract

The effect of spinal transections on the preovulatory release of gonadotropins and PRL was investigated in female rats. A preovulatory rise in serum LH, FSH and PRL and subsequent ovulation were prevented by complete spinal transections (CST) at high thoracic levels (T3-T7), but not at low thoracic and lumbar levels (T8-L5), performed at 1000-1230 h on proestrus.Norepinephrine (NE) concentrations in the preoptic-anterior hypothalamic area at 1700-1800 h on proestrus were also significantly reduced by CST at high thoracic levels, but not at lumbar levels. Either electrochemical stimulation of the suprachiasmatic part of the preoptic area or NE injection into the third ventricle at 1400-1500 h on proestrus restored ovulation in animals with CST at high thoracic levels. Animals with CST at lumbar levels exhibited relatively regular 4-day cycles, but those with CST at high thoracic levels showed prolonged periods of diestrous (8-20 days) before they resumed cyclicity.In the case of partial transections, bilateral transections of the lateral columns, but not transections of the dorsal or medial columns, of the spinal cord at T4-T5 significantly blocked the preovulatory gonadotropin release and the occurrence of ovulation.Unilateral transections of the lateral columns of the spinal cord or unilateral electrolytic lesions of the ventrolateral part of the medulla oblongata failed to block ovulation. When combinations of them were performed ipsilaterally, ovulation occurred, but when they were performed contralaterally, the incidence of ovulation was significantly decreased. These results suggest that the ascending neural pathway in the lateral columns of the spinal cord projecting to the ipsilateral VLMO participates in the neural mechanisms controlling the preovulatory release of gonadotropins and PRL by maintaining NE levels in the preoptic-anterior hypothalamic area.

Galactorrhoea and amenorrhoea due to an intradural neurinoma originating from a thoracic intercostal nerve radicle

“…Suckling or mammary stimulation increases PRL secretion (Noel et al, 1974;Herman et al, 1981;Reichlin, 1992). In animal experiments, transection of the spinal cord at T3-T7, particularly bilateral transection of lateral column of spinal cord, blocks mammary stimulation of PRL release (Nishihara et al, 1983). No change in PRL release is found in lesions of the spinal cord at T8-L5.…”

“…The tumour might have directly stimulated the afferent nerve fibres of intercostal nerves. The tumour also compressed the spinal cord, but this was not the cause of the increased PRL secretion, since transection of spinal cord at T8 or below has no effect on prolactin secretion (Nishihara et al, 1983). Wang et al (1992) reported that hyperprolactinaemia was seen in 17 of 63 patients with spinal cord injury.…”