Infundibular Lesion and Pars Intermedia Activity in the Tadpole

Abstract

Vunder 1 reported that the transplantation of a single hypophysis into an hypophysectomized Axolotl led to an excessive development of pigmentation. He ascribed this result to traumatic stimulation in the operation and supported his view by showing that the same result followed pricking the gland with a needle. In connection with the development of anterior lobe function in the tadpole, one of us 2 has confirmed and extended Vunder's findings. His interpretation, however, seemed unacceptable since it was there found that transplantation of even primordia into the embryo led to the development of the pigmentation weeks later and also because the effect often persisted as long as the animal could be kept, in many cases over 4 months. In a brief report of some of this material 3 it was suggested that the pituitary is under some restraint in its normal site, from which it is released on transplantation. It was further suggested that the source of this inhibition might be the nerve tract from the hypothalamus to the pars nervosa and intermedia. This tract usually called the supra-optico-hypophyseal tract has been found by the authors in the frog.

Recently we have been able to put this theory to a test through having developed an operative approach to the tadpole's pituitary. The operation was performed in Rana sylvatica tadpoles by exposing the entire dorsum of the brain, cutting the olfactory and one or both optic nerves and lifting the brain out sufficiently to make possible the manipulation of the infundibulum by the anterior approach. In the experimental animals the infundibulum was partly or completely destroyed by pinching with fine forceps and where possible plucking out part of the tissue. In the controls the infundibulum was merely slightly manipulated though the rest of the operation was carried out as in the experimentals.