This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Caraty, A. Articles by Skinner, D. C. Search for Related Content PubMed PubMed Citation Articles by Caraty, A. Articles by Skinner, D. C.

Gonadotropin-Releasing Hormone in Third Ventricular Cerebrospinal Fluid: Endogenous Distribution and Exogenous Uptake

Unité Mixte de Recherche 6175 (A.C.), Physiologie de la Reproduction et des Comportements (Institut National de la Recherche Agronomique/Centre National de la Recherche Scientifique/Université Tours/Haras Nationaux), 37380, Nouzilly, France; and Neurobiology Program and Department of Zoology and Physiology (D.C.S.), University of Wyoming, Laramie, Wyoming 82071

Address all correspondence and requests for reprints to: Alain Caraty, Unité Mixte de Recherche 6175, Physiologie de la Reproduction et des Comportements (Institut National de la Recherche Agronomique/Centre National de la Recherche Scientifique/Université Tours/Haras Nationaux), 37380, Nouzilly, France. E-mail: caraty{at}tours.inra.fr; or Donal C. Skinner, Neurobiology Program and Department of Zoology and Physiology, University of Wyoming, Laramie, 1000 East University Avenue, Department 3166, Wyoming 82071. E-mail: dcs{at}uwyo.edu.

GnRH is detectable in the cerebrospinal fluid (CSF), but its source remains unidentified. Previous studies have harvested CSF for GnRH analysis from the median eminence region, but it is unknown whether GnRH in CSF is restricted to this region. If CSF-GnRH plays a physiological role, through volume transmission, to communicate with brain regions that express GnRH receptors but are not evidently innervated by GnRH neurons, then it is essential to establish whether GnRH is more pervasive throughout the cerebroventricular system. Three cannulae were placed in the supraoptic, infundibular, and pineal recesses of the third ventricle. GnRH was undetectable in lateral ventricle CSF. GnRH pulses were detected in all ewes in infundibular recess CSF, but at sites more rostral (supraoptic) and caudal (pineal), GnRH pulse frequency and amplitude significantly (P < 0.05) decreased. A GnRH surge was evident in CSF collected simultaneously from all cannulae, but the amplitude was greatest (P < 0.05) at the infundibular recess. A final study established whether iv administered GnRH enters the CSF. A 250-ng GnRH dose did not affect CSF-GnRH concentrations (1.6 ± 0.3 pg/ml), but 2.5 µg (2.7 ± 0.2 pg/ml; P < 0.001) and 1 mg (38.5 ± 10.6 pg/ml; P < 0.05) significantly increased CSF-GnRH concentrations. The present study shows: 1) the median eminence region is likely to be the major, if not only, source of GnRH entering the cerebroventricular system; and 2) exogenous GnRH crosses the blood-brain barrier, but extremely high doses are required to elevate CSF concentrations to physiological levels. Thus, CSF-GnRH may affect sites that are closer in proximity to the infundibular recess region than previously thought.