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  • Author or Editor: Katalin Köves x
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Introduction

It was previously shown that intracerebroventricular administration of pituitary adenylate cyclase-activating polypeptide (PACAP) prior to GnRH mobilization in proestrus prevents ovulation in rats. In this study, we examined whether PACAP given intranasally could influence luteinizing hormone (LH) and prolactin (PRL) surges and ovulation.

Methods

On the day of proestrus PACAP, β-cyclodextrin (modifier of blood–brain barrier) or PACAP + β-cyclodextrin was applied intranasally between 12:30 and 13:00. Blood samples were taken at 16:00, 18:00, and 20:00 for measuring plasma hormone levels. In the next morning, the expelled ova were counted. β-Cyclodextrin was also administered to male and diestrous female rats between 12:30 and 13:00 and blood was taken at 18:00.

Results

PACAP prevented LH and PRL surges and ovulation in about half of the rats, β-cyclodextrin alone more effectively prevented ovulation. When PACAP and β-cyclodextrin were administered together, more rats ovulated like when PACAP given alone. β-Cyclodextrin did not influence LH and PRL levels in diestrous females; however, in males, it significantly enhanced PRL level.

Discussion

Not only the intracerebroventricular, but the intranasal application of PACAP prevented ovulation. β-Cyclodextrin alone is more effective than PACAP and enhances PRL levels in male rats. PACAP and β-cyclodextrin given together weaken each other’s effect. β-Cyclodextrin, as excipient of various drugs, has to be used carefully in human medications.

Open access

The aim of experiments was to characterize the neurons of the autonomic chain that innervates the nipple and the mammary gland of lactating rats using retrograde transynaptic virus labeling and neurotransmitter and neuropeptide immunohistochemistry. Two days after injection of green fluorescence protein labeled virus in two nipples and underlying mammary glands, labeling was observed in the ipsilateral paravertebral sympathetic trunk and the lateral horn. Three days after inoculation the labeling appeared in the brain stem and the hypothalamic paraventricular nucleus. Above the spinal cord the labeling was bilateral. A subpopulation of virus labeled cells in the paraventricular nuclei synthesized oxytocin. Labeled neurons in the lateral horn showed cholinergic immunoreactivity. These cholinergic neurons innervated the paravertebral ganglia where the virus labeled neurons were partially noradrenergic. The noradrenergic fibers in the mammary gland innervate the smooth muscle wall of vessels, but not the mammary gland in rats. The neurons in the lateral horn receive afferents from the brain stem, and paraventricular nucleus and these afferents are noradrenergic and oxytocinergic. New findings in our work: Some oxytocinergic fibers may descend to the neurons of the lateral horn which innervate noradrenergic neurons in the paravertebral sympathetic trunk, and in turn these noradrenergic neurons reach the vessels of the mammary gland.

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