ADRENALECTOMY INCREASES REDUCED NICOTINAMIDE ADENINE-DINUCLEOTIDE PHOSPHATE-DIAPHORASE ACTIVITY IN THE RAT SPINAL TRIGEMINAL SUBNUCLEUS CAUDALIS

Neurons exhibiting reduced nicotinamide adenine dinucleotide phosphate -diaphorase activity (NADPHd) were quantified at 500 mu m rostrocaudal intervals in spinal trigeminal nucleus (Vsp) of adenalectomized (ADX) , ADX + corticosterone, and sham-ADX rats 6-12 days after surgery. NAD PHd neurons were found predominantly in Vsp subnucleus caudalis (Vc) a nd in dorsomedial subnucleus oralis. ADX significantly increased the n umber of NADPHd neurons in superficial laminae of Vc, an effect revers ed by chronic corticosterone replacement. ADX effects on NADPHd in sup erficial laminae of Vc but not in deep laminae of Vc or in the periobe x region of Vsp paralleled previously observed sites of ADX enhancemen t of noxious stimulus-induced Fos-like immunoreactivity. The results i ndicate that chronic changes in adrenal steroid status regulate NADPHd , a mechanism that may both derive from changes in nitric oxide syntha se expression and influence the processing of nociceptive information by central trigeminal neurons.