Striatal interneurons expressing calretinin, parvalbumin or NADPH-diaphorase: a comparative study in the rat, monkey and human

The present study is aimed at evaluating the relative number and comparing the pattern of distribution of interneurons containing calretinin (CR), par valbumin (PV) or NADPH-d in the striatum of rats, squirrel monkeys and huma ns, A series of adjacent coronal sections taken at three comparable rostroc audal levels in the three species were treated to reveal the three neuronal markers and the density of each type of chemospecific interneurons was ana lyzed with a computerized image analysis system. In primates, the most abun dant interneurons were those expressing CR. The ratio of CR+ /PV+ neurons w as approximately 2-3:1 compared to a ratio of 3-4:1 for CR+/NADPH-d+ neuron s. In contrast, the most frequently encountered interneurons in the rat str iatum were these expressing PV. In rodents, all three interneurons were mor e abundant rostrally than caudally, but CR+ neurons displayed a particularl y striking rostrocaudal decreasing gradient. In monkeys and humans, the thr ee striatal intrneurons were distributed rather uniformly rostrocaudally, b ut CR+ and PV+ interneurons were significantly more numerous in the caudate nucleus than in the putamen in humans. In monkeys, only PV+ neurons were m ore abundant in the caudate nucleus than in putamen. Overall, the density o f the three striatal interneurons was much higher in monkeys than in rats a nd humans. These results reveal important species differences in respect to the relative density and pattern of distribution of striatal interneurons. These findings should be taken into account when evaluating the effect of neurodegenerative processes on cell densities in the human striatum or when studying animal models of the such diseases, (C) 2000 Elsevier Science B.V . All rights reserved.