title: Spatiotemporal Changes of Neuronal Responses in the Primary Somatosensory Cortex to Noxious Tail Stimulation in Awake and Pentobarbital-Anesthetized Rats.
abstract: Primary somatosensory cortex (SI) is a key area in the processing of nociceptor inputs to our consciousness. To clarify the columnar and laminar organization of SI for pain processing, we compared spatiotemporal changes in neuronal activities of the primary sensorimotor cortex (SmI) of the rat in response to noxious laser heat stimulation applied to the mid-tail. Longitudinal and vertical array microelectrodes were chronically implanted in the cerebral cortex. Evoked neuronal activities, including intracortical local field potentials (LFP) and ensemble single-unit activity (SU) around SmI were simultaneously recorded. The effect of pentobarbital on the neuronal responses was evaluated in comparison with the neuronal responses in conscious animals to explore the potential substrate of nociceptive processing in the conscious state. The results from the experiment with longitudinal microelectrode arrays indicated that noxious stimulation induced a neuronal response which was spread widely around the SmI of the conscious rat, and the range of neuronal responses was limited to the tail region of the SmI under anesthesia. The results from the experiment with vertical microelectrode arrays showed the universal neuronal responses through all cortical layers of the SmI in conscious rats, and sodium pentobarbital suppressed these neuronal responses in the supragranular layers significantly relative to the deeper layers and basal activity. These results imply that a wider range of cortical activation, both in the horizontal or vertical dimension, might be important for nociceptive processing in the conscious state.
authors.affiliation: Department of Physiology, School of Medicine, College of Medicine, Tzu Chi University, Hualien 97004, Taiwan, Republic of China.
authors.forename: Chung-Chih
authors.initials: CC
authors.lastname: Kuo
authors.affiliation: Department of Life Science, National Taiwan University, Taipei 10617, Taiwan, Republic of China.
authors.forename: Jye-Chang
authors.initials: JC
authors.lastname: Lee
authors.affiliation: Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 11031, Taiwan, Republic of China.
authors.forename: Ruei-Jen
authors.initials: RJ
authors.lastname: Chiou
authors.affiliation: Department of Anatomy, School of Medicine, China Medical University, Taichung 40402, Taiwan, Republic of China.
authors.forename: Meng-Li
authors.initials: ML
authors.lastname: Tsai
authors.affiliation: Department of Life Science, National Taiwan University, Taipei 10617, Taiwan, Republic of China.
authors.forename: Chen-Tung
authors.initials: CT
authors.lastname: Yen
mesh_terms: D000758:Anesthesia; D000818:Animals; D000069280:Electrocorticography; D005260:Female; D006358:Hot Temperature; D054020:Lasers, Gas; D009474:Neurons / Q000502:physiology; D059225:Nociception / Q000502:physiology*; D010424:Pentobarbital; D020318:Rats, Long-Evans; D013003:Somatosensory Cortex / Q000502:physiology*; D013312:Stress, Physiological; D013623:Tail
chemical_list: D010424:Pentobarbital