Modulation of somatosensory evoked potentials during wake-sleep states and spike-wave discharges in the rat.
OBJECTIVE
To clarify the cortical evoked responses in the primary somatosensory cortex of the rat under states of waking, slow-wave sleep (SWS), paradoxical sleep (PS), and spike-wave discharges (SWDs), which are associated with absence seizure.


METHODS
Somatosensory evoked potentials (SEPs) in response to single- and paired-pulse stimulations under waking, SWS, PS, and SWDs were compared. SEPs to a single-pulse stimulus with regard to cortical spikes of sleep spindles and SWDs were also evaluated.


METHODS
Twenty Long Evans rats.


METHODS
Single- and paired-pulse innocuous electrical stimulations were applied to the tail of rats with chronically implanted electrodes in the primary somatosensory cortex and neck muscle under waking, SWS, PS, and SWDs.


RESULTS
SEPs displayed distinct patterns under waking/PS and SWS/SWDs. The short-latency P1-N1 wave of the SEP was severely impeded during SWDs but not in other states. Reduction of the P1-N1 magnitude to the second stimulus of the paired-pulse stimulus for interstimulus intervals of < or = 300 milliseconds appeared in waking and PS states, but the decrease occurred only at particular interstimulus intervals under SWS. Interestingly, augmentation was found under SWDs. Moreover, cyclic augmentation of the P1-N1 magnitude was associated with spindle spikes, but cyclic reduction was observed with SWD spikes.


CONCLUSIONS
Changes in SEPs are not only behavior dependent, but also phase locked onto ongoing brain activity. Distinct short-term plasticity of SEPs during sleep spindles or SWDs may merit further studies for seizure control and tactile information processing.
Shaw
Fu-Zen
FZ
Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan. fzshaw@yahoo.com.tw
Lee
Su-Ying
SY
Chiu
Ted H
TH
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D004832:Epilepsy, Absence / Q000503:physiopathology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D017286:Polysomnography; D051381:Rats; D020318:Rats, Long-Evans; D012890:Sleep / Q000502:physiology; D013003:Somatosensory Cortex / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology*