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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 99/5/1658    most recent 00334.2005v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Cheng, Y.-W. Articles by Su, C.-K. Search for Related Content PubMed PubMed Citation Articles by Cheng, Y.-W. Articles by Su, C.-K.

GABA_B-receptor-mediated suppression of sympathetic outflow from the spinal cord of neonatal rats

¹Institute of Biomedical Sciences, Academia Sinica, and ²Department of Anesthesiology, Taipei Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan

Submitted 23 March 2005 ; accepted in final form 14 July 2005

Using a splanchnic nerve-spinal cord preparation in vitro that could spontaneously generate sympathetic nerve discharge (SND), we investigated the roles of intraspinal GABA_B receptors in the regulation of SND. Despite an age-dependent difference in sensitivity, bath applications of baclofen (Bac; GABA_B-receptor agonist) consistently reduced SND in a concentration-dependent manner. The drug specificity of Bac in activation of GABA_B receptors was verified by application of its antagonist saclofen (Sac) or CGP-46381 (CGP). Sac or CGP alone did not change SND. However, in the presence of Sac or CGP, the effects of Bac on SND inhibition were reversibly attenuated. The splanchnic sympathetic preganglionic neuron (SPN) was recorded by blind whole cell, patch-clamp techniques. We examined Bac effects on electrical membrane properties of SPNs. Applications of Bac reduced excitatory synaptic events, induced membrane hyperpolarizations, and inhibited SPN firing. In the presence of 12 mM Mg²⁺ or 0.5 µM TTX to block Ca²⁺- or action potential-dependent synaptic transmissions, applications of Bac induced an outward baseline current that reversed at –29 ± 6 mV. Because the K⁺ equilibrium potential in our experimental conditions was –100 mV, the Bac-induced currents could not simply be attributed to an alteration of K⁺ conductance. On the other hand, applications of Bac to Cs⁺-loaded SPNs reduced Cd²⁺-sensitive and high-voltage-activated inward currents, indicating an inhibition of voltage-gated Ca²⁺ currents. Our results suggest that the activation of intraspinal GABA_B receptors suppresses SND via a mixture of ion events that may link to a change in Ca²⁺ conductance.

intermediolateral cell column; hypertension; postnatal maturation; autonomic nervous system

This article has been cited by other articles:

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				C.-M. Ho and C.-K. Su Ketamine Attenuates Sympathetic Activity Through Mechanisms not Mediated by N-Methyl-d-Aspartate Receptors in the Isolated Spinal Cord of Neonatal Rats. Anesth. Analg., March 1, 2006; 102(3): 806 - 810. [Abstract] [Full Text] [PDF]