The Ability of Certain Adrenocortical Hormones to Potentiate the Vasoconstrictor Action of Nor-Adrenaline on the Conjunctival Vessels in the Rabbit and in Man

FROM the observations of Ashton and Cook (1952) on the terminal vessels of the rabbit ear and those of Fritz and Levine (1951) and Zweifach, Shorr, and Black (1953) on the vessels of the mesoappendix of the adrenalectomized rat, it has been proved that the bloodvessels show an increased sensitivity to the local administration of nor-adrenaline when the animals have previously undergone general treatment with cortisone or ACTH.It has further been established that the adrenocortical steroids increase the muscular tone by implementing the pressor action of the nor-adrenaline.An increase in pressure after intravenous injection of nor-adrenaline has been demonstrated in the adrenalectomized dog (Ramey, Goldstein, and Levine, 1951) and also in man after the previous administration ofhigh doses ofcortisone (Kurland and Freedburg, 1951) or desoxycorticosterone acetate.Reis (1960) has recently examined the responses of the vessels of the bulbar con- junctiva of normal subjects to nor-adrenaline after previous local application of adrenocortical hormones.He found that both cortisone and hydrocortisone poten- tiated the action of nor-adrenaline, and that deltacortisone produced an even more marked increase of sensitization.The considerable importance of these results in the field of ophthalmology en- couraged us to examine the problem further.The present research has been carried out on normal rabbits and subsequently on normal human subjects.Methods (a) Animal Experiments (I) Eleven normal male rabbits weighing from 1 8 to 2 kg.were used.The conjunctival vessels were observed by means of the Haag-Streit slit lamp, using a magnification of 47 diameters, which showed not only the arterioles and meta- arterioles, but also the precapillary sphincters, capillaries, venules, and arteriovenous shunts.In each animal, a limited area of the conjunctiva was examined and observations were made in that area alone, in order to eliminate local variations which might take place in different regions of the conjunctiva.The sensitivity of the precapillary sphincters and of the meta-arterioles was first tested by using serial dilutions of nor- adrenaline, buffered to pH 7A4 and introduced successively into the conjunctival sac,