Age-related changes in the NADPH-diaphorase-positive neuronal perikarya of the dorsolateral column of the periaqueductal gray in the rat.

The distribution of reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) positive neuronal perikarya in the rostral, middle and caudal parts of the dorsolateral periaqueductal gray (DLPAG) in 3-, 12- and 26-month-old rats was compared by means of histochemistry and computer assisted image analysis. The total number, the maximum diameter, the cross-sectional area and the optical density (OD) of the NADPH-d positive neurons were analyzed. The results demonstrate that there are no significant differences in any of the investigated parameters between the left and the right parts of the same age and of the same level. The total cell number in the DLPAG of 26-month-old rats was significantly decreased in comparison with 3- and 12-month-old rats. The cross-sectional area increased between 3 and 12 months of age, and decreased in 26-month-old rats in comparison with 12-month-old rats. The OD increased significantly between 3 and 12 months of age, and decreased significantly between 12 and 26 months of age only at caudal level. The observed mild changes could lead to alterations in the brain physiology of aging.