ACTIVATION OF THE ANTERIOR HYPOPHYSIS BY ELECTRICAL STIMULATION IN THE RABBIT1

Publisher Website
Google Scholar
Abstract
Stimulation of the cervical sympathetic trunk in 27 un-anesthetized mature [female] rabbits has given no evidence that the release of luteinizing hormone from the ant. lobe of the hypophysis can be induced by normal activity of these nerves. The possibility that sensory fibers of the vagus might reflexly affect the activity of the ant. lobe, as they are said to do for the posterior, is also apparently negated by a series of 22 cervical vagus stimulations, following none of which were ovarian changes observed. Direct unipolar stimulation of the ant. pituitary gland in 19 animals, with voltage and current up to an avg. maximum of 201 mv./0.083 ma. induced ovulation only in those animals in which evidence of considerable spread to the C. N. S. was observed. Bipolar stimulation of the pituitary gland, with avg. voltage and current of the same order of magnitude as those used in unipolar stimulation, was accompanied by no evidence of spread to the C. N. S., and failed to effect ovulation in all 7 cases. Bipolar stimulation of the hypothalamus, however, under the identical conditions found ineffective on the hypophysis, induced ovulation in 3 of 4 animals. The above expts. confirm the findings of others that the hypothalamus plays a major role in the release of luteinizing hormone from the ant. lobe of the hypophysis. However, the difference in the electrical excitability of the hypophysis and of the hypothalamus, as shown here, is interpreted as indicating that the hypothalamus does not exert a direct neural control over the ant. hypophysis; rather, the presence of a long humoral link seems to be implied by the results of these expts.