Postnatal changes in Bax-immunoreactivity and apoptosis of the rat trigeminal primary neurons

The developmental changes of Bax protein-like immunoreactivity (Bax-ir) and naturally occurring cell death were investigated in the trigeminal primary neurons of rats, in the first 2 postnatal weeks. At 1 day postpartum, the trigeminal primary neurons exhibited intense cytoplasmic Bax-ir. A densitometric analysis indicated >95% of cells exhibited an ir-density (the staining intensity as compared to the background level) higher than 1.5. By 2 weeks the ir-density significantly decreased with >95% lower than 1.5, that was similar to the adult level. A nick-end labeling method revealed DNA fragmentation in apoptotic trigeminal primary neurons in newborn rats. During the first 11 days the percentage of apoptotic cells was highly correlated to the postnatal days with a regression line y = -0.083x + 0.877 (r = 0.976). A possible role of Bax in neonatal rat primary neurons is discussed.