NITRIC-OXIDE REDUCES THE THERMOGENIC CHANGES INDUCED BY LATERAL HYPOTHALAMIC-LESION

The experiment described here tests the effect of intracerebroventricu lar (icv) injection of nitric oxide (NO) precursors, such as L-arginin e (L-arg) and nitroprusside (NP), on the thermogenic changes induced b y lesion of the lateral hypothalamus (LH). The firing rate of the nerv es innervating interscapular brown adipose tissue (IBAT), along with I BAT and colonic temperatures (T-IBAT and T-C) were monitored in uretha ne-anaesthetized male Sprague-Dawley rats lesioned in the LH. These va riables were measured before and after an icy injection of 4 mu mol L- arg or 400 nmol NP. The same variables were also monitored in: a) lesi oned rats with icv administration of saline; b) sham-lesioned animals with icy injection of L-arg or NP; c) sham-lesioned rats with icv inje ction of saline. The results show that L-arg or NP injection reduces t he increases in firing rate, T-IBAT, and T-C induced by LH lesion. The se findings suggest that NO plays a key role in the thermogenic change s following LH lesion.