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lüll TRPV1 receptor mediates glutamatergic synaptic input to dorsolateral periaqueductal gray (dl-PAG) neurons Xing J; Li JJ Neurophysiol 2007[Jan]; 97 (1): 503-11The purpose of this study was to determine the role of transient receptor potential vanilloid type 1 (TRPV1) receptor in modulating neuronal activity of the dorsolateral periaqueductal gray (dl-PAG) through excitatory and inhibitory synaptic inputs. First, whole cell voltage-clamp recording was performed to obtain the spontaneous miniature excitatory postsynaptic currents (mEPSCs) and inhibitory postsynaptic currents (mIPSCs) of the dl-PAG neurons. As 1 microM of capsaicin was applied into the perfusion chamber, the frequency of mEPSCs was increased from 3.21 +/- 0.49 to 5.64 +/- 0.64 Hz (P < 0.05, n = 12) without altering the amplitude and the decay time constant of mEPSCs. In contrast, capsaicin had no distinct effect on mIPSCs. A specific TRPV1 receptor antagonist, iodo-resiniferatoxin (i-RTX, 300 nM), decreased the frequency of mEPSCs from 3.51 +/- 0.29 to 2.01 +/- 0.2 Hz (P < 0.05, n = 8) but did not alter the amplitude and decay time. In addition, i-RTX applied into the chamber abolished the effect of capsaicin on mEPSC of the dl-PAG. In another experiment, spontaneous action potential of the dl-PAG neurons was recorded using whole cell current-clamp methods. Capsaicin significantly elevated the discharge rate of the dl-PAG neurons from 3.03 +/- 0.38 to 5.96 +/- 0.87 Hz (n = 8). The increased firing activity was abolished in the presence of glutamate N-methy-D-aspartate (NMDA) and non-NMDA antagonists, 2-amino-5-phosphonopentanoic acid, and 6-cyano-7-nitroquinoxaline-2,3-dione. The results from this study provide the first evidence indicating that activation of TRPV1 receptors increases the neuronal activity of the dl-PAG through selective potentiation of glutamatergic synaptic inputs.|Action Potentials/drug effects/physiology[MESH]|Afferent Pathways/drug effects/*metabolism/ultrastructure[MESH]|Animals[MESH]|Autonomic Pathways/drug effects/metabolism/ultrastructure[MESH]|Capsaicin/pharmacology[MESH]|Cardiovascular Physiological Phenomena/drug effects[MESH]|Diterpenes/pharmacology[MESH]|Excitatory Amino Acid Antagonists/pharmacology[MESH]|Excitatory Postsynaptic Potentials/drug effects/physiology[MESH]|Female[MESH]|Glutamic Acid/*metabolism[MESH]|Inhibitory Postsynaptic Potentials/drug effects/physiology[MESH]|Male[MESH]|Neurons/drug effects/*metabolism/ultrastructure[MESH]|Organ Culture Techniques[MESH]|Pain/chemically induced/metabolism/physiopathology[MESH]|Patch-Clamp Techniques[MESH]|Periaqueductal Gray/drug effects/*metabolism/ultrastructure[MESH]|Presynaptic Terminals/drug effects/*metabolism/ultrastructure[MESH]|Rats[MESH]|Rats, Sprague-Dawley[MESH]|Synaptic Transmission/drug effects/physiology[MESH]|TRPV Cation Channels/agonists/antagonists & inhibitors/*metabolism[MESH] |