Effects of sympathicolytic and sympathicomimetic drugs on pineal ultrastructure in the domestic pig.

The effects of a 4-day administration of two sympathicolytic (alpha-methyl-p-tyrosine, propranolol) and three sympathicomimetic (clorgyline, isoproterenol, dobutamine) drugs on the ultrastructure of the pineal gland in the domestic pig were examined. The morphological changes in the pinealocytes of the experimental groups mainly concerned cytoplasmic dense bodies, primary lysosomes, multivesicular bodies, dense core vesicles, and smooth endoplasmic reticulum. These structures seemed to be under direct or indirect control by the adrenergic nervous system. The relative volume of dense bodies in pinealocyte perikarya increased after administration of alpha-methyl-p-tyrosine as well as propranolol and decreased on treatment with clorgyline. The decrease in the relative volume of primary lysosomes in pinealocyte perikarya was noted in pigs treated with clorgyline and isoproterenol. The number of multivesicular bodies in pinealocyte perikarya decreased after administration of alpha-methyl-p-tyrosine. The numerical density of dense core vesicles in pinealocyte perikarya increased after treatment with clorgyline. Administration of isoproterenol and clorgyline resulted in the presence of wide cisterns of smooth endoplasmic reticulum. Narrow cisterns of this form of endoplasmic reticulum and lamellar whorls were observed after treatment with alpha-methyl-p-tyrosine in pinealocytes with large dense bodies. The presence of multilamellar structures was a characteristic feature of the pinealocytes of pigs treated with isoproterenol and dobutamine. Administration of alpha-methyl-p-tyrosine and clorgyline resulted in the appearance of pinealocytes which differed in number, size, and structure of dense bodies.