Protein markers in the microcyst of the posteroventral cochlear nucleus of the gerbil.

Microcysts are most evident in the posteroventral and anteroventral cochlear nuclei (PVCN and AVCN) of the Mongolian gerbil. The origin and contents of the microcyst are not elucidated at present. The present study investigated the possible inclusions in the microcyst by employing immunocytochemical labeling to localize the existence of various protein markers. Thirty and 100 microm thick sections were used to substitute and reconstruct between 6 and 20 paraffin serial sections, respectively. In 30-microm-thick slice sections, immunoreactivity of glial fibrillary acidic protein (GFAP-IR), mitochondria inner membrane (MCA-In-IR), S-100 (S-100-IR), serotonin (5-HT-IR), myelin proteolipid protein (PLP-IR) and substance P (SP-IR) abutted on the perimeter of the microcyst. The immunolabeled SP-positive cells were adjacent to the evagination of the microcyst. In 100-microm-thick slice sections, immunoreactivity of nitric oxide synthase (NOS-IR) and somatostatin (SOM-IR) mainly precipitated as flocculent structures in the small to medium-sized microcysts. 5-HT-IR also precipitated as an elongated flocculent stalk adjacent to the large microcyst or randomly distributed in the neuropil. The findings suggest that GFAP, MCA-In, S-100, 5-HT, PLP, SP, NOS and SOM may be involved in modulating the physiological functions and maintaining micro-environmental homeostasis of the microcyst in the cochlear nucleus of the gerbil.