Slow oscillation of membrane currents mediated by glutamatergic inputs of rat somatosensory cortical neurons: in vivo patch-clamp analysis.
Using in vivo patch-clamp technique, the slow oscillation of membrane currents was characterized by its synaptic nature, correlation with electroencephalogram (EEG) and responses to different anesthetic agents, in primary somatosensory cortex (SI) neurons in urethane-anesthetized rats. In more than 90% of the SI neurons, the slow oscillation of the inward currents (0.1-2.5 Hz) with the duration of several hundreds of a millisecond was observed at the holding membrane potential of -70 mV. The reversal potential of the inward currents was approximately 0 mV and was suppressed by application of an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor antagonist. In most cases (> 90%) the inward current was synchronized with positive wave of the surface EEG recorded from ipsilateral and even contralateral cortical regions. The frequency as well as duration of the slow oscillation decreased by a volatile anesthetic agent, isoflurane (1.5-5.0%), and excitatory postsynaptic currents (EPSCs) were almost abolished at the highest concentration. Intraperitoneal injection of pentobarbital (25 mg/kg) also decreased the frequency of the slow oscillation without affecting short EPSCs. When gamma-aminobutyric acid A (GABA(A)) receptors were activated by local microinjection of muscimol (3 x 10(-3) m, 1-10 microL) into the thalamus, the frequency of the slow oscillation markedly decreased, but was not abolished completely. These findings suggest that the slow oscillation of the inward currents is generated by the summation of glutamatergic EPSCs, and affected by isoflurane and pentobarbital differently. In addition, GABAergic system in the thalamus can affect the frequency, but is not essentially implicated in the genesis of the slow oscillation.
Doi
Atsushi
A
Department of Integrative Physiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Mizuno
Masaharu
M
Katafuchi
Toshihiko
T
Furue
Hidemasa
H
Koga
Kohei
K
Yoshimura
Megumu
M
D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004569:Electroencephalography / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D007530:Isoflurane / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010424:Pentobarbital / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism; D013003:Somatosensory Cortex / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D000777:Anesthetics; D018691:Excitatory Amino Acid Antagonists; D018755:GABA Agonists; D018091:Receptors, AMPA; D011963:Receptors, GABA-A; D018698:Glutamic Acid; D007530:Isoflurane; D010424:Pentobarbital