P.1.c.048 Nitric oxide modulate methylphenidate-induced disruption on prepulse inhibition of the acoustic startle in swiss mice

Abstract

We investigated the central role of nitric oxide and AngII on thermoregulation in rats (Rattus norvegicus, Sabra strain,) undergoing heat-stress in euhydration or hypohydration (water deprivation, −10% b.wgt). Experimental rats received AngII (100 pm), 7-nitroindazole—an antagonist of neuronal nitric oxide synthase (7NI—100 nm), or AngII+7NI in a 5-μl bolus intracerebroventricularly (i.c.v.) under light chloroform anesthesia; untreated control rats received saline or DMSO (5%). We used three experimental paradigms: (1) heat defense responses [salivation (STsh), vasodilatation (VTsh) temperature thresholds and heat-endurance] in conscious, heat-stressed (39 °C) rats; (2) Western immunoblotting to detect AngII AT1 and AT2 receptors and nNOS protein expression; (3) real-time PCR to measure gene transcripts. In the in vivo experiment, 7NI decreased thermoregulatory thresholds, namely, NO had a reciprocal effect that was more pronounced during hypohydration (e.g. euhydration: STsh: −0.7±0.01 °C, hypohydration: −0.9±0.18 °C, p<0.05). AngII decreased STsh by 0.9±0.18 °C (p<0.05) upon euhydration but increased it in hypohydration (+1.7±0.28 °C, p<0.05). A novel finding was the involvement of AT2 receptors in thermoregulation, which was more pronounced upon hypohydration. The response to NO was mediated via AT1 and AT2 receptors signaling, as well as independently. A synthesis of the results from all experimental paradigms suggests (1) a dominant influence (decrease) of NO on AT1 receptors, thereby changing AT1/AT2 receptor ratio and their signaling pathway; primarily upon hypohydration; (2) an influence of AngII (increase) on receptor density, more pronounced during hypohydration, at both gene transcription and translation levels; and (3) an effect of AngII on nNOS protein levels, implying a mutual effect of AngII and NO.