The rostral raphe pallidus (rRPa) contains sympathetic premotor neurons controlling thermogenesis in brown adipose tissue (BAT). We sought to determine if a tonic activation of glycineA receptors (GlyAR) in the rRPa contributes to the inhibitory regulation of BAT SNA and of cardiovascular parameters in anesthetized rats. Nanoinjection of the GlyAR antagonist, strychnine (STR), into the rRPa of intact rats increased BAT sympathetic nerve activity (SNA, peak: +495%), BAT temperature (TBAT, +1.1 ºC), expired CO2, (+0.4 %), core body temperature (TCORE, +0.2 ºC), arterial pressure (MAP, +4 mmHg) and heart rate (HR, +57 bpm). STR into rRPa in rats with a post-dorsomedial hypothalamus transection produced similar increases in BAT thermogenic and cardiovascular parameters. Glycine (GLY) nanoinjection into the rRPa evoked a potent inhibition of the cooling-evoked increases in BAT SNA (nadir: -74 %), TBAT (-0.2 ºC), TCORE (-0.2 ºC), expired CO2 (-0.2 %), MAP (-8 mmHg), and HR (-22 bpm), but had no effect on the increases in these variables evoked by STR nanoinjection into rRPa. Nanoinjection of GABA into the rRPa inhibited the STR evoked BAT SNA (nadir: -86 %), and reduced the expired CO2 (-0.4 %). Blockade of glutamate receptors in rRPa reduced the STR-evoked increases in BAT SNA (nadir: -61 %), TBAT (-0.5 ºC), expired CO2 (-0.3 %), MAP (-9 mmHg) and HR (-33 bpm). We conclude that a tonically active glycinergic input to the rRPa contributes to the inhibitory regulation of the discharge of BAT sympathetic premotor neurons and of BAT thermogenesis and energy expenditure.
- glycineA receptor
- dorsomedial hypothalamus
- Copyright © 2017, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology