Distribution of calbindin-D28k, neuronal nitric oxide synthase, and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) in the lateral nucleus of the sheep amygdaloid complex

This study describes calbindin-D28k (CB), neuronal nitric oxide synthase (nNOS), and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) expression in the lateral nucleus of the sheep amygdaloid complex. Double immunofluorescence protocol was used in order to determine whether there is colocalization of CB and nNOS. The CBimmunoreactive (IR) neuronal population was composed especially of non-pyramidal neurons, but a few pyramidal cells were also present. The non-pyramidal neurons showed a multipolar and, occasionally, a fusiform morphology. The comparison between single-labeled CB-IR non-pyramidal neurons and cells belonging to CB-IR neuronal population showed they were identical for morphology, mean size, and distribution. The single-labeled CB-IR non-pyramidal neurons were only the 17.8% of the total non-pyramidal neurons counted. The nNOS-IR neuronal population was represented by non-pyramidal multipolar and fusiform neurons. Singlelabeled nNOS-IR non-pyramidal neurons had the same morphology, mean area, and distribution as cells belonging to nNOS-IR neuronal population. Single-labeled nNOS-IR non-pyramidal neurons were more numerous than single-labeled CB-IR, and represented the 73.7% of total non-pyramidal neurons counted. NADPH-d-positive cells had the same morphology and distribution as the nNOS-IR neurons. Double immunolabeling (CB/nNOS) was found mostly in non-pyramidal multipolar neurons and only in a few nonpyramidal fusiform cells. These neurons had a mean perikaryal area significantly higher and significantly smaller than that of single-labeled nNOS and single-labeled CB-IR non-pyramidal neurons, respectively. CB and nNOS coexist only in a minority of non-pyramidal neurons (8.5%). The 32.4% of all CB-IR non-pyramidal neurons were nNOS-positive; only 10.4% of nNOS-IR non-pyramidal neurons were CB-positive. These results indicate that CB and nNOS are expressed by selective neurons and that the majority of nNOS-IR non-pyramidal neurons are lacking in CB.