12 11 Morphological and Immunohistochemical Stud - ies on the Pineal Gland of the Donkey ( Equus asinus

The pineal glands of donkey were light beige to dark brown, fusiform structure. It lies at the pineal recess caudal to the splenium of the corpus callosum and caudodorsal to the third ventricle, just in front of the rostral colliculi and in between the para hippocampal gyrus. The pineal gland was supplied from the caudal choroidal artery and branches from artery of corpus callosum. The venous drainage by the pineal veins flowing into the cerebral vein. The glial fibrillary acidic protein (GFAP) and S100 protein immunoreactivity was restricted to glial cells. They showed a heterogeneous pattern of immunostaining for (GFAP) and S100. It was conspicuous around the large pineal cyst and corpora arenacea, where the pinealocytes formed clusters, widely separated by aggregations of GFAP and S100 immunoreactive glial cells and their processes. They were also striking around blood vessels. At the periphery of the gland, only a relatively few GFAP and S100 positive cell bodies and/or processes were seen in the marginal portions of the parenchyma. S100 immunoreactive cells showed similar morphological characteristics to those of GFAP-reactivity, but their immunoreactivity was denser. Immunolabeling of the pinealocyte marker synaptophysin was intense, especially in pinealocytes at perivascular space. Several highly synaptophysin-positive blotch of variable extent were a conspicuous feature in pinealocyte throughout the gland. While it was less dense in