Environmental temperature changes enhance the reduced nitotinamide adenine dinucleotide phosphate-diaphorase activity in the paraventricular nucleus of the rat hypothalamus

The nitrergic neurons of the paraventricular nucleus of the hypothalamus show changes following a variety of experimental conditions. In the last year, it has been suggested that nitric oxide has a possible role in the regulation of hibernation in the toad. Based upon these studies we attempt to elucidate whether or not changes in the environmental temperature affect the histochemical expression of the nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity in the mammalian paraventricular nucleus. Cryostat sections were cut and processed for the histochemical detection of the NADPH-diaphorase activity. Following exposure to low temperature (4°C) (12 and 24 hours), statistical analysis displayed a marked increase in the number of NADPH-diaphorase neurons, especially in the posterior magnocellular and the lateral parvicellular subdivisions. These data indicate that NADPH- diaphorase-activity in the paraventricular nucleus is influenced by the environmental temperature.