PINEALOCYTE ULTRASTRUCTURE IN MUTANT MICE THAT LACK SYMPATHETIC INNERVATION TO THE PINEAL-GLAND

Pinealocyte synaptic ribbons (SR) and dense-cored vesicles (DCV) were quantitated in mice that have developmental deficiences in the sympath etic innervation of the pineal gland due to a null mutation for the p7 5 low-affinity NGF receptor (NGFR). SR exhibited a significant increas e whereas there was a significant decline in the frequency of DCV in m utant mice. These findings support the hypothesis that pinealocyte SR and DCV are regulated by neural mechanisms associated with the sympath etic system. Ultrastructural characteristics of pinealocytes in mutant s included degenerative changes that culminated in the breakdown of ce llular components and the accumulation of flocculent-containing vesicl es within the cytoplasm. Ribosomal lamellar complexes were also common ly seen in pinealocytes of mutant rats. Although the mutant pineal gla nd exhibited signs of metabolic imbalances, the cytoarchitecture of th e gland (e.g., vascular compartment) and differentiation of the cells were generally unaffected by developmental deficiencies in the gland's innervation.