Effects of temporary bilateral ligation of the internal carotid arteries on the low- and high-frequency somatic evoked potentials in the swine.
OBJECTIVE
We studied effects of a temporary bilateral ligation of the internal carotid arteries on the subcortical and cortical structures of the somatosensory system by examining the thalamic input and postsynaptic cortical responses contained in the somatic evoked potentials (SEPs) recorded from the primary somatosensory cortex (SI) of the juvenile piglets in vivo. We predicted that the ligation should differentially affect these structures due to differences in blood supply.


METHODS
The SEPs between 1 and 3000 Hz were measured in the SI cortex with a multichannel electrode array before, during and after a 20 min bilateral ligation of the internal carotid arteries in the swine under a barbiturate anesthesia.


RESULTS
The ligation differentially affected the thalamic input and the cortical responses contained in the high-frequency signals (HFSs) between 400 and 2000 Hz. The amplitude of the thalamic input did not change, but the amplitudes of the cortical HFS postsynaptic to the thalamic inputs decreased immediately after start of ligation, recovering over the next 30-90 min. The latency showed a small, but significant increase for several minutes after the start of ligation for both the thalamic input and cortical responses. The ligation increased the latency and reduced the amplitude of the peak of the first cortical response in the wideband SEP corresponding to human N20.


CONCLUSIONS
The HFS is useful for distinguishing selective effects of the temporary ligation on the subcortical and cortical structures of the somatosensory system. Since the porcine N20 starts after the presynaptic HFS, it was not useful in differentiating thalamic and cortical effects.


CONCLUSIONS
The HFS may open a new window in studying the cortical physiology in humans.
Wang
Yaozhi
Y
Department of Neurology and Biomedical Research and Integrative NeuroImaging (BRaIN Imaging) Center, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA.
Hosler
Gregory
G
Zhang
Tongsheng
T
Okada
Yoshio
Y
D000818:Animals; D002545:Brain Ischemia / Q000503:physiopathology; D002343:Carotid Artery, Internal / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D008026:Ligation; D008297:Male; D009666:Nose / Q000502:physiology; D017661:Receptors, Presynaptic / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology; D013552:Swine; D013788:Thalamus / Q000502:physiology
D017661:Receptors, Presynaptic