THE MEASUREMENT OF HYPOTHALAMIC RELEASING HORMONE CONTENT AND ACTIVITY IN THE UNANAESTHETIZED RAT BY MEANS OF CAROTID ARTERY CANNULATION

Abstract

ABSTRACT To gain insights into quantitative changes in hypothalamic substances which affect the function of the anterior hypophyseal lobe, we developed a technique for carotid cannulation allowing sequential measurements of plasma levels of an affected hormone after injection of such a factor. The principle involves the use of a previously cannulated rat in an unanaesthetized unstressed condition The hypothalamic extract or LH-RH injected into the cannulas of such animals leads to rapid peaks of LH in peripheral blood removed from the same cannulas within 6 to 8 min, followed by a slow decrease. At least 50% of the peak value is usually found within 3 min. The technique yields quantitatively reproducible results, and appears suitable for measuring relative potencies of test extracts against pure standards and, within as yet undetermined limits, for kinetic studies.