Pineal Blood Content and Its Experimental Modification

¹ From the Department of Zoology, University of California, Berkeley, California

The blood content of over one thousand rat pineals in various physiological and pharmacological states was determined from acid hematein-stained sections in which the number of erythrocytes per cubic millimeter of pineal tissue was calculated. The lowest mean blood content appears in normal animals between 3 and 5 weeks of age, but castration and administration of estradiol fail to produce significant effects in either sex. Significant pineal vasodilation is produced by injection of adenosine or picrotoxin and by ether anesthesia. No significant vasoconstriction was ever observed, but noradrenaline even in small doses inhibits the vasodilation during ether anesthesia. The blood content of the pineal cortex varies from 1.2 to 2.0 times that of the medulla and the net differences in the two areas after various treatments are generally the same. The blood content of the rat pineal is usually about one-fifth that of the anterior lobe of the hypophysis and one-third that of the posterior lobe.