TY - JOUR
T1 - Spinal GABA(A) receptors do not mediate the sympathetic baroreceptor reflex in the rat
AU - Goodchild, Ann K.
AU - Van Deurzen, Bart T.M.
AU - Sun, Qi Jian
AU - Chalmers, John
AU - Pilowsky, Paul M.
PY - 2000/7/1
Y1 - 2000/7/1
N2 - Activation of baroreceptors causes efferent sympathetic nerve activity (SNA) to fall. Two mechanisms could account for this sympathoinhibition: Disfacilitation of sympathetic preganglionic neurons (SPN) and/or direct inhibition of SPN. The roles that spinal GABA and glycine receptors play in the baroreceptor reflex were examined in anesthetized, paralyzed, and artificially ventilated rats. Spinal GABA(A) receptors were blocked by an intrathecal injection of bicuculline methiodide, whereas glycine receptors were blocked with strychnine. Baroreceptors were activated by stimulation of the aortic depressor nerve (ADN), and a somatosympathetic reflex was used as control. After an intrathecal injection of vehicle, there was no effect on any measured variable or evoked reflex. In contrast, bicuculline caused a dose-dependent increase in arterial pressure, SNA, phrenic nerve discharge, and it significantly facilitated the somatosympathetic reflex. However, bicuculline did not attenuate either the depressor response or sympathoinhibition evoked after ADN stimulation. Similarly, strychnine did not affect the baroreceptor-induced depressor response. Thus GABA(A) and glycine receptors in the spinal cord have no significant role in baroreceptor-mediated sympathoinhibition.
AB - Activation of baroreceptors causes efferent sympathetic nerve activity (SNA) to fall. Two mechanisms could account for this sympathoinhibition: Disfacilitation of sympathetic preganglionic neurons (SPN) and/or direct inhibition of SPN. The roles that spinal GABA and glycine receptors play in the baroreceptor reflex were examined in anesthetized, paralyzed, and artificially ventilated rats. Spinal GABA(A) receptors were blocked by an intrathecal injection of bicuculline methiodide, whereas glycine receptors were blocked with strychnine. Baroreceptors were activated by stimulation of the aortic depressor nerve (ADN), and a somatosympathetic reflex was used as control. After an intrathecal injection of vehicle, there was no effect on any measured variable or evoked reflex. In contrast, bicuculline caused a dose-dependent increase in arterial pressure, SNA, phrenic nerve discharge, and it significantly facilitated the somatosympathetic reflex. However, bicuculline did not attenuate either the depressor response or sympathoinhibition evoked after ADN stimulation. Similarly, strychnine did not affect the baroreceptor-induced depressor response. Thus GABA(A) and glycine receptors in the spinal cord have no significant role in baroreceptor-mediated sympathoinhibition.
KW - Aortic depressor nerve
KW - Arterial pressure
KW - Phrenic nerve discharge
KW - Sympathetic nerve activity
UR - http://www.scopus.com/inward/record.url?scp=0033886483&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.2000.279.1.r320
DO - 10.1152/ajpregu.2000.279.1.r320
M3 - Article
C2 - 10896896
AN - SCOPUS:0033886483
SN - 0363-6119
VL - 279
SP - R320-R331
JO - American Journal of Physiology: Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology: Regulatory Integrative and Comparative Physiology
IS - 1
ER -