Distribution and Proportion of Immunoreactive Neuron Specific Enoclase Containing Cells in the Rat Pineal Gland

The distribution and proportion of cytoplasm containing immunoreactive neuron specific enolase (NSE) in the rat pineal have been investigated. Step serial sections of the pineal glands of 7 male Sprague-Dawley rats were stained for NSE using an indirect immunoperoxidase method. The volumes of the pineals and of the regions containing reactive cells were derived from the distance between sections and the sum of the corresponding sectional areas of camera lucida drawings. The proportion of the NSE areas actually consisting of NSE reactive cytoplasm was measured using an image array processor.Cytoplasm reactive for NSE was consistently localized to the posterior and dorsal aspects of the pineal. To express this in quantitative terms the volume of reactive cytoplasm in the anterior and posterior halves of the glands were determined separately. It was found that on the average 79 % of the total NSE volume was found in the posterior 46% of the pineal volume.The volume occupied by NSE positive cells ranged from 0.02x10-3 mm3 to 42.7x10-3mm3 per pineal. The average volume was 2.1% of the pineal volume, which was 0.334 mm3 (S.D. 0.21). Pineal volume also exhibited a wide range from 0.151 to 0.727 mm3. This great variability in both the volume of pineal and of NSE reactive cytoplasm is discussed, and it is suggested that when the factors that control this variability are identified, pineal functions will be more readily understood.