Simultaneous BOLD fMRI and local field potential measurements during kainic acid-induced seizures.
OBJECTIVE
To investigate how kainic acid-induced epileptiform activity is related to hemodynamic changes probed by blood oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI).


METHODS
Epileptiform activity was induced with kainic acid (KA) (10 mg/kg, i.p.), and simultaneous fMRI at 7 Tesla, and deep electrode local field potential (LFP) recordings were performed from the right hippocampus in awake and medetomidine-sedated adult Wistar rats.


RESULTS
Recurrent seizure activity induced by KA was detected in LFP both in medetomidine-sedated and awake rats, even though medetomidine sedation reduced the mean duration of individual seizures as compared to awake rats (33 ± 24 and 46 ± 34 s, respectively, mean ± SD p < 0.01). KA administration also triggered robust positive BOLD responses bilaterally in the hippocampus both in awake and medetomidine-sedated rats; however, in both animal groups some of the seizures detected in LFP recording did not cause detectable BOLD signal change.


CONCLUSIONS
Our data suggest that medetomidine sedation can be used for simultaneous fMRI and electrophysiologic studies of normal and epileptic brain function, even though seizure duration after medetomidine administration was shorter than that in awake animals. The results also indicate that neuronal activity and BOLD response can become decoupled during recurrent kainic acid-induced seizures, which may have implications to interpretation of fMRI data obtained during prolonged epileptiform activity.
Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
Antti M
AM
Airaksinen
Shahryar K
SK
Hekmatyar
Neil
N
Jerome
Juha-Pekka
JP
Niskanen
Joanna K
JK
Huttunen
Asla
A
Pitkänen
Risto A
RA
Kauppinen
Olli H
OH
Gröhn
D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000187:drug effects; D001931:Brain Mapping; D004195:Disease Models, Animal; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D006624:Hippocampus / Q000187:drug effects / Q000503:physiopathology; D007091:Image Processing, Computer-Assisted; D007608:Kainic Acid / Q000633:toxicity*; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D051381:Rats; D017208:Rats, Wistar; D012640:Seizures / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D014851:Wakefulness / Q000187:drug effects / Q000502:physiology
D018690:Excitatory Amino Acid Agonists; D010100:Oxygen; D007608:Kainic Acid