PARVALBUMIN, CALRETININ AND CARBONIC-ANHYDRASE IN THE TRIGEMINAL AND SPINAL PRIMARY NEURONS OF THE RAT

The cell-body size of parvalbumin-immunoreactive (-ir) primary neurons was measured in the trigeminal (TG) and lumber dorsal root ganglia (DRG). In the DRG, parvalbumin-ir was mostly detected in large cells (94% in the range of 600-2800 mu m(2)). Parvalbumin-ir TG cells were smaller than similar DRG cells and yet parvalbumin-ir TG cells of < 400 mu m(2) (2.86%) were rare. Trichrome stains for parvalbumin, calretinin (CR) and carbonic anhydrase (CA), and for parvalbumin, calcitonin gene-related peptide (CGRP) and CB were performed to estimate possible overlap of these substances. Virtually all parvalbumin-ir DRG cells contained CA activity while a small subpopulation (28.5%) of CR-ir DRG cells lacked CA activity. All the CR-ir DRG cells that exhibited CA were also ir for parvalbumin. 31.1% of parvalbumin-ir DRG cells exhibited CR-ir while 71.5% of CR-ir DRG cells showed parvalbumin-ir. All the CR-ir DRG cells of < 400 mu m(2) lacked CA activity and parvalbumin-ir while all those of > 800 mu m(2) exhibited both activities. similar to 30% of CR-ir DRG cells in the size range of 400-800 mu m(2) co-expressed CA. DRG cells co-expressing parvalbumin and CGRP were rare (similar to 1%). As was the case for the DRG, most of parvalbumin-ir TG cells exhibited CA activity (89.24%) and lacked CGRP-ir (96.6%). CR-ir TG cells were also subdivided into two groups; one with and the other without co-expression of CA. Unlike in the DRG, however, co-expression of parvalbumin and CR could never be detected in the TG.