Discussions 119 



gonadotropins on the one hand and of LTH (or prolactin) on the other, at any rate 

 in the rat, seemed to be alternative functions. There are various circumstances in 

 which one can inhibit the secretion of gonadotropins, for instance by administering 

 reserpine or by high doses of estrogen, or especially by transplanting the pituitary 

 into the anterior chamber of the eye or under the capsule of the kidney. Here one 

 gets inhibition of gonadotropin release or virtual disappearance of gonadotropic 

 function while at the same time the release of prolactin is unhindered or even enhanced. 

 On the other hand, if the transplanted pituitary is replaced in its natural position 

 LTH secretion ceases and regular estrous cycles are re-established. Can it be that 

 the gonadotropes, nourished as they seem to be by their natural proximity to the 

 median eminence, exert by local humoral action an inhibitory influence on the acido- 

 phils, including those which secrete prolactin? This idea should be susceptible of 

 experimental test. 



I should like to end these remarks by asking Professor Harris, referring to his very 

 interesting experiments with median eminence extracts, whether he has tried the 

 administration of extracts of whole posterior pituitary lobe by his very fascinating 

 and elegant pituitary plumbing technique? In addition I would like to know whether 

 he has made any pituitary infusions with adrenalin, noradrenalin, histamine or 

 serotonin ? 



Dr. Geoffrey Harris: We have started preliminary experiments infusing posterior 

 pituitary preparations. We started with "Pitressin", but since this may be contaminated 

 with anterior pituitary hormones we have recently obtained a highly purified prepara- 

 tion of lysine vasopressin from Dr. A. V. Schally in Houston, and also some synthetic 

 arginine vasopressin from Dr. V. du Vigneaud. The results at the moment are too 

 few to warrant any comment. 



With regard to the other point raised, concerning intra-pituitary infusions of 

 adrenalin and noradrenalin. Dr. B. T. Donevan and myself worked a few years back 

 on this point (/. Physiol. 132, 577-585, 1956). The technique differed a little in the 

 previous experiments from that presently used. Infusions were made under anesthesia 

 and through glass needles. However, we found that such infusions into the pituitary 

 glands of rabbits did not result in ovulation. 



Dr. William Hansel: Dr. Folley has raised two interesting questions which deserve 

 comment. The first of these concerns the role of prolactin in the cow. There are at 

 least two experiments suggesting that prolactin is not luteotrophic in the bovine. 

 Wisconsin workers have attempted and failed to prolong the length of the estrous 

 cycle by daily injections of prolactin beginning at about the 15th day of the cycle 

 and continuing through the 22nd day. In some of our own experiments we have 

 attempted and failed to overcome the ability of oxytocin to produce precocious estrus 

 by giving concurrent prolactin injections. The prolactin used was of ovine origin. It 

 is possible that the dosages used in both of these experiments were too low. 



Dr. Folley has also raised a question concerning the purity of the oxytocin prepara- 

 tions used in our work. In most of the experiments Armour's purified preparation 

 was used. In addition, the estrous cycle was shortened in several cases by injections 

 of a synthetic oxytocin preparation (Syntocinon, Sandoz Corp.). This preparation 

 was free of vasopressin, but probably contained some peptides other than oxytocin. 

 None of the preparations used possessed any measurable gonadotropic potency. 



Chairman Nelson: I know that Dr. Segal wants to say something at this time, but I am 

 going to ask him to be brief. 



Dr. Sheldon Segal: I think it is worthwhile spending more time on the subject of androgen- 

 sterilized rats for several reasons. This experimental condition bears on our under- 

 standing of the normally occurring differences in pattern of gonadotropin release 

 between males and females of a given species. As Dr. Barraclough has indicated, it 

 also suggests important considerations with respect to localization of neural areas 

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