Comparative investigation of neuronal nitric oxide synthase immunoreactivity in rat and human claustrum

- This is the first comparative study of neuronal nitric oxide synthase immunoreactivity in the rat and human claustrum.
- The aim of this study is to compare neuronal NOS immunoreactivity, morphology and dendritic characteristics in the rat and human claustrum.
- NOS-immunoreactive neurons in rats and humans displayed a statistically significant difference in their dendritic characteristics.

We compared the distribution, density and morphological characteristics of nitric oxide synthase-immunoreactive (NOS-ir) neurons in the rat and human claustrum. These neurons were categorized by diameter into three main types: large, medium and small. In the human claustrum, large neurons ranged from 26 to 40 μm in diameter, medium neurons from 20 to 25 μm and small neurons from 13 to 19 μm. In the rat claustrum, large neurons ranged from 19 to 23 μm in diameter, medium neurons from 15 to 18 μm and small neurons from 10 to 14 μm. The cell bodies of large and medium neurons varied broadly in shape - multipolar, elliptical, bipolar and irregular, consistent with a projection neuron phenotype. The small neurons were most seen as being oval or elliptical in shape, resembling an interneuron phenotype. Based on a quantitative comparison of their dendritic characteristics, the NOS-ir neurons of humans and rats displayed a statistically significant difference.