SUMMARY
The effects of the pineal gland on the ultrastructure of pituitary gonadotrophs have been studied. The results of luteinizing hormone (LH) estimations in the same rats have already been reported (Clementi, De Virgiliis, Fraschini & Mess, 1966; Fraschini, Mess & Martini, 1968). It was found that pinealectomy in normal animals greatly increases the pituitary content of gonadotrophins without significantly changing the ultrastructure of gonadotrophs.
Pinealectomy in castrated animals did not induce an increase in pituitary gonadotrophin stores above the level found after castration alone; the ultrastructure of the 'castration cells' was also unchanged.
Implants of melatonin or of pineal tissue into the median eminence or the reticular formation of the midbrain of castrated animals reduced the pituitary content of LH and, morphologically, the gonadotrophs reverted to a nearly normal state with a reduction in volume of the cisternae of the endoplasmic reticulum.
The relationship between gonadotrophin content and the ultrastructural appearance of the gonadotrophs is discussed.
Intercellular Communication Within the Rat Anterior Pituitary: XIV Electron Microscopic and Immunohistochemical Study on the Relationship Between the Agranular Cells and GnRH Neurons in the Dorsal Pars Tuberalis of the Pituitary Gland