TY - JOUR
T1 - Hypoxic activation of arterial chemoreceptors inhibits sympathetic outflow to brown adipose tissue in rats
AU - Madden, C. J.
AU - Morrison, S. F.
PY - 2005/7/15
Y1 - 2005/7/15
N2 - In urethane-chloralose anaesthetized, neuromuscularly blocked, artificially ventilated rats, we demonstrated that activation of carotid chemoreceptors inhibits the elevated levels of brown adipose tissue (BAT) sympathetic nerve activity (SNA) evoked by hypothermia, by micro-injection of prostaglandin E2 into the medial preoptic area or by disinhibition of neurones in the raphe pallidus area (RPa). Peripheral chemoreceptor stimulation with systemic administration of NaCN (50 μg in 0.1 ml) or with hypoxic ventilation (8% O2-92% N2, 30 s) completely inhibited BAT SNA. Arterial chemoreceptor-evoked inhibition of BAT SNA was eliminated by prior bilateral transections of the carotid sinus nerves or by prior inhibition of neurones within the commissural nucleus tractus solitarii (commNTS) with glycine (40 nmol/80 nl) or with the GABAA receptor agonist muscimol (160 pmol/80 nl; 77 ± 10% attenuation), or by prior blockade of ionotropic excitatory amino acid receptors in the commNTS with kynurenate (8 nmol/80 nl; 82 ± 10% attenuation). Furthermore, activation of commNTS neurones following local micro-injection of bicuculline (30 pmol/60 nl) completely inhibited the elevated level of BAT SNA resulting from disinhibition of neurones in the RPa. These results demonstrate that hypoxic stimulation of arterial chemoreceptor afferents leads to a inhibition of BAT SNA and BAT thermogenesis through an EAA-mediated activation of second-order, arterial chemoreceptor neurones in the commNTS. Peripheral chemoreceptor-evoked inhibition of BAT SNA could directly contribute to (or be permissive for) the hypoxia-evoked reductions in body temperature and oxygen consumption that serve as an adaptive response to decreased oxygen availability.
AB - In urethane-chloralose anaesthetized, neuromuscularly blocked, artificially ventilated rats, we demonstrated that activation of carotid chemoreceptors inhibits the elevated levels of brown adipose tissue (BAT) sympathetic nerve activity (SNA) evoked by hypothermia, by micro-injection of prostaglandin E2 into the medial preoptic area or by disinhibition of neurones in the raphe pallidus area (RPa). Peripheral chemoreceptor stimulation with systemic administration of NaCN (50 μg in 0.1 ml) or with hypoxic ventilation (8% O2-92% N2, 30 s) completely inhibited BAT SNA. Arterial chemoreceptor-evoked inhibition of BAT SNA was eliminated by prior bilateral transections of the carotid sinus nerves or by prior inhibition of neurones within the commissural nucleus tractus solitarii (commNTS) with glycine (40 nmol/80 nl) or with the GABAA receptor agonist muscimol (160 pmol/80 nl; 77 ± 10% attenuation), or by prior blockade of ionotropic excitatory amino acid receptors in the commNTS with kynurenate (8 nmol/80 nl; 82 ± 10% attenuation). Furthermore, activation of commNTS neurones following local micro-injection of bicuculline (30 pmol/60 nl) completely inhibited the elevated level of BAT SNA resulting from disinhibition of neurones in the RPa. These results demonstrate that hypoxic stimulation of arterial chemoreceptor afferents leads to a inhibition of BAT SNA and BAT thermogenesis through an EAA-mediated activation of second-order, arterial chemoreceptor neurones in the commNTS. Peripheral chemoreceptor-evoked inhibition of BAT SNA could directly contribute to (or be permissive for) the hypoxia-evoked reductions in body temperature and oxygen consumption that serve as an adaptive response to decreased oxygen availability.
UR - http://www.scopus.com/inward/record.url?scp=22744458868&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=22744458868&partnerID=8YFLogxK
U2 - 10.1113/jphysiol.2005.086322
DO - 10.1113/jphysiol.2005.086322
M3 - Article
C2 - 15878945
AN - SCOPUS:22744458868
SN - 0022-3751
VL - 566
SP - 559
EP - 573
JO - Journal of Physiology
JF - Journal of Physiology
IS - 2
ER -