Monoamines and seizures: microdialysis findings in locus ceruleus and amygdala before and during amygdala kindling

We used microdialysis to determine extracellular concentrations of norepine phrine (NE), dopamine (DA) and serotonin (5-HT) before and during a 1-day a mygdala kindling paradigm. Subjects were young cats (<1 year old; n=8; 6 fe male, 2 male). Consecutive 5-min samples (2 <mu>l/min infusion rate) were o btained from left amygdala and ipsilateral locus ceruleus complex (LC) unde r 3 experimental conditions lasting 1-h each (n=12 samples per cat per cond ition): (1) just before amygdala stimulation (baseline), (2) during focal a fterdischarge (AD) and (3) during generalized AD. ADs were elicited by elec trical stimulation applied to establish thresholds immediately before dialy sate collection as well as during each sample collected in focal vs. genera lized AD conditions. Sample concentrations were time-adjusted to correspond with sleep vs. waking state and/or focal vs. generalized ADs. Seizure acti vity was indexed by AD threshold (mA) and duration (s) as well as number an d duration of specific clinically evident (behavioral) seizure manifestatio ns. Main results were: (1) Lower baseline concentrations (fmoles per sample ) of NE, DA and 5-HT correlated with subsequent increases in duration of fo cal and generalized AD as well as number of behavioral seizure correlates. (2) When compared to baseline levels, NE, DA and 5-HT concentrations signif icantly increased only in amygdala during focal AD and in both amygdala and LC during generalized AD. (3) NE and 5-HT concentrations were higher than DA at both collection sites and were selectively associated with increased wakefulness throughout the study. (C) 2001 Elsevier Science B.V. All rights reserved.