Postictal behavioural impairments are due to a severe prolonged hypoperfusion/hypoxia event that is COX-2 dependent
- University of Calgary, Canada
- Catholic University of Health and Allied Sciences, Tanzania
Figures
Figure 1 with 1 supplement
Seizures induce severe postictal hypoxia.
(A) Local tissue oxygenation in the hippocampus of an awake, freely-moving rat (blue). Green denotes normoxia while red denotes severe hypoxia. (B) Representative oxygen profile before, during, and …
Figure 1—figure supplement 1
Postictal severe hypoxia generalizes to other seizure models.
Both stimulations resulted in severe hypoxia. A 40 s seizure was elicited with MES stimulation and resulted in 104.1 min of severe hypoxia (red). Following 2 min of 3 Hz stimulation, hippocampal pO2 …
Figure 2 with 1 supplement
Seizures cause postictal vessel constriction in an in vitro preparation and reduced blood flow (hypoperfusion) in vivo.
(A) Location of implants for simultaneous blood flow and pO2 recordings. These two probes were placed at opposing angles to leave room for cable attachment. (B) The simultaneous measurement of mean …
Figure 2—figure supplement 1
Post-seizure administration of nifedipine prevents severe postictal hypoxia.
(A) Nifedipine (15 mg/kg) was administered immediately after a seizure. No differences were observed in seizure duration, however nifedipine initiated a quicker return to baseline pO2(n = 5). (B) …
Figure 3 with 1 supplement
Representative seizure-specific local postictal hypoperfusion in clinical epilepsy.
(A) ASL-010, 26 year old female with drug resistant focal epilepsy. Ictal EEG recording on a longitudinal bipolar montage with left frontal seizure onset and spread to the right frontal region. …
Figure 3—figure supplement 1
Clinical postictal hypoperfusion is more severe with longer seizures.
(A) Cerebral blood flow from baseline and postictal ASL scans. Each point represents in individual. Group mean ± SEM are expressed in grey. Patient number is displayed on the left of the …
Figure 4 with 1 supplement
COX-2 activity during a seizure is required for postictal severe hypoxia.
(A) COX-2 expression in sagittal section. Hippocampal inset is displayed (see B–D). Scale bar = 2 mm. (B–D) Contents of inset from (A). Many NeuN-expressing neurons (B) in DG and hilus express COX-2 …
Figure 4—figure supplement 1
COX-1 or postictal COX-1/2 inhibition do not inhibit severe hypoxia.
(A) SC-560 (20 mg/kg) pre-administration did not significantly alter seizure duration or the resulting oxygen profile (n = 5). (B) Quantification of (A). No differences in the severe hypoxia were …
Figure 5
Genetic knockdown of COX-2 function prevents postictal severe hypoxia.
(A) COX-2 proteins from wild-type and mutant mice (PTGS2Y385F) displayed as a schematic. Both mice have functional peroxidase (POX). Mutants have a point mutation in the cyclooxygenase (COX) active …
Figure 6
Preventing postictal severe hypoxia prevents behavioral impairments.
(A) Experimental timeline for neocortex experiments. Rats were injected with vehicle or nifedipine 30 min prior to a baseline hang time measurement. Neocortical seizures (or sham) were then elicited …
Author response image 1
Susceptibility of Area Below Baseline analysis to changes in baseline pO2.
(A) Seizure duration is not correlated with total area under curve (R square=0.000013, p=0.99). (B) Instead, the baseline pO2 is strongly correlated with the area below baseline (R square=0.52, ***p<…
Author response image 2
Comparing area below baseline analyses with pre- and post-administration of nifedipine.
(A) Pre-administration of nifedipine had no effect on area below baseline. (B) Post-administration of nifedipine significantly reduced the area below baseline (p<0.01).
Tables
Table 1
Characteristics of patients recruited to ASL study.
Patient | Age | Age at Seizure Onset | Structural MRI findings |
|---|---|---|---|
ASL-001 | 38 | 34 | Normal |
ASL-003 | 41 | 13 | Lesion in the right superior temporal gyrus, resolving? |
ASL-004 | 25 | 5 | Normal |
ASL-006 | 33 | 7 | Normal |
ASL-007 | 33 | 29 | Bilateral subependymal heterotopias along lateral ventricle right > left |
ASL-008 | 42 | 22 | Right amygdala enlargement, Right occipital cavernoma |
ASL-009 | 40 | 9 | Normal |
ASL-010 | 26 | 1 | Left frontal malformation of cortical development |
ASL-011 | 22 | 14 | Normal |
ASL-012 | 20 | 0.5 | Postsurgical changes in the right frontal lobe, right anterior temporal lobectomy |
Table 2
Concordance of postictal ASL hypoperfusion with brain areas involved in the seizure. EEG localization of ictal activity was determined by an Epileptologist based on scalp EEG. GTC denotes when a …
Patient | EEG localization of seizure [duration (S)] | Area of maximal hypoperfusion for ASL quantification | ROI volume (cm3) | Concordant |
|---|---|---|---|---|
ASL-001 | Left temporal [71] | Left temporal | 2.52 | yes |
ASL-003 | Unclear [26] | No Change | 1.45 | n/a |
ASL-004 | Left frontocentral [87] | Left superior posterior temporal | 0.31 | yes |
ASL-006 | Left fronotemporal [114] | Left insula, left anterior temporal | 1.46 | yes |
ASL-007 | GTC, Left hemisphere. Maximal posterior temporo-parietal [64] | Multifocal bihemispheric | 1.35 | yes |
ASL-008 | GTC, Right temporo-occipital [155] | Multifocal bihemispheric | 1.63 | yes |
ASL-009 | Left fronto-central [85] | Multifocal bihemispheric | 0.76 | yes |
ASL-010 | GTC, Bifrontal, maximum left [166] | Left frontal | 3.82 | yes |
ASL-011 | Left fronto-temporal [56] | No Change | 1.10 | n/a |
ASL-012 | Bitemporal right>left [30] | Multiple areas over right temporal posterior and superior to resection cavity | 2.19 | yes |
Table 3
Investigation of mechanisms involved in postictal severe hypoxia.
Drug | Principle known mechanism of action | Δ severity of hypoxia |
|---|---|---|
Nifedipine (15 mg/kg) | L-type Ca2+ Channel Blocker | +78.82 ± 7.632% *** |
Nifedipine (15 mg/kg postictal) | +87.33 ± 10.49% ** | |
Acetaminophen (250 mg/kg) | COX-1/2 Inhibitor | +99.88 ± 0.12% *** |
Acetaminophen (150 mg/kg) | +88.88 ± 7.355% *** | |
Acetaminophen (50 mg/kg) | +48.85 ± 26.61% | |
Acetaminophen (250 mg/kg postictal) | −3.33 ± 17.29% | |
Ibuprofen (20 mg/kg) | +99.23 ± 0.396% *** | |
Celecoxib (20 mg/kg) | COX-2 Inhibitor | +67.26 ± 27.42% * |
SC-560 (20 mg/kg) | COX-1 Inhibitor | +19.42 ± 15.37% |
Celecoxib (20 mg/kg) + SC-560 (20 mg/kg) | COX-2 and COX-1 Inhibitors | +95.80 ± 4.21% *** |
Acetaminophen (250 mg/kg) + Nifedipine (15 mg/kg) | COX-1/2 Inhibitor + L-type Ca2+ Channel Blocker | +100 ± 0.00% *** |
CAY-10526 (2 mg/kg) | Prostaglandin E2 Synthesis Inhibitor | +41.72 ± 9.94% ** |
Seratrodast (10 mg/kg) | Thromboxane A2 Receptor Antagonist | −12.91 ± 44.08% |
Ozagrel (10 mg/kg) | Thromboxane A2 Synthesis Inhibitor | +21.24 ± 16.42% |
2-APB (3 mg/kg) | IP3r Antagonist + TRP Channel Blocker | +45.27 ± 18.44% * |
Chelerythrine Chloride (15 mg/kg) | PKC Inhibitor | +25.54 ± 29.90% |
Milrinone (3 mg/kg) | Phosphodiesterase-3 Inhibitor | −10.74 ± 34.31% |
Sildenafil (15 mg/kg) | Phosphodiesterase-5 Inhibitor | −19.34 ± 14.03% |
SKA-31 (10 mg/kg) | IKCa Channel Activator | −1.50 ± 12.68% |
Paxilline (2.5 mg/kg) | BKCa Channel Blocker | +19.55 ± 14.98% |
L-Arginine (500 mg/kg) | Nitric Oxide Precursor | −5.05 ± 14.08% |
Fasudil (10 mg/kg) | Rho Kinase Inhibitor | −53.07 ± 17.27% * |
-
All drugs were delivered by intraperitoneal injection pre-seizure (unless otherwise stated).
-
Statistics reported as different from chance (one sample T-test).
-
*p < 0.05, **p<0.01, ***p<0.001.
-
+ number indicates inhibition of hypoxia.
-
− number indicates potentiation of hypoxia.
Table 4
Effect of Anti-Seizure drugs on postictal severe hypoxia.
Drug | Principal known mechanism of action | Δ severe hypoxia |
|---|---|---|
Ethosuximide (300 mg/kg) | T-type Ca2+ Channel Blocker | +30.53 ± 19.31% * |
Topiramate (50 mg/kg) | Na+ Channel Blocker, GABA Enhancement, AMPA Inhibition | +4.34 ± 14.07% |
Bumetanide (2.5 mg/kg) | NKCC1 Transporter Inhibitor | −0.92 ± 14.72% |
Phenobarbital (30 mg/kg) | GABA Receptor Agonist | −1.22 ± 13.90% |
Levetiracetam (250 mg/kg) | Glutamate Release Inhibition | −14.85 ± 19.71% |
Phenytoin (75 mg/kg) | Na+ Channel Blocker | −15.76 ± 17.00% |
Lamotrigine (15 mg/kg) | Na+ Channel Blocker | −20.95 ± 17.13% |
Valproate (150 mg/kg) | Na+ Channel Blocker, GABA Enhancement | −24.89 ± 22.65% |
-
All drugs were delivered by intraperitoneal injection pre-seizure.
-
Statistics reported as different from chance (one sample T-test).
-
*p<0.05.
-
+ number indicates inhibition of hypoxia.
-
-number indicates potentiation of hypoxia.
Table 5
Stereotaxic coordinates for surgical implantation.
Experiment | Anterior(+)/ Posterior(−) | Lateral Right(+)/Left(−) | Ventral (from brain surface) |
|---|---|---|---|
Rat Dorsal Hippocampus | Electrode: −3.0 mm Optode: −3.5 mm | Electrode: 0.5 mm Optode: 3.5 mm | Electrode: 3.5 mm Optode: 3.5 mm |
Rat Dorsal Hippocampus with LDF | Electrode: −3.0 mm Optode: −5.0 mm LDF probe: −3.0 mm | Electrode: 0.5 mm Optode: 2.2 mm LDF probe: 3.5 mm | Electrode: 3.5 mm Optode: 3.5 mm LDF probe: 3.5 mm |
Rat Ventral Hippocampus | Electrode: −4.5 mm Optode: −3.0 mm | Electrode: 4.5 mm Optode: 3.5 mm | Electrode: 6.5 mm Optode: 3.5 mm |
Rat Ventral Hippocampus w/ Cannula | Electrode: −4.5 mm Optode: −3.0 mm Cannula: - 5.8 mm | Electrode: 4.5 mm Optode: 3.5 mm Cannula: −4.5 mm | Electrode: 6.5 mm Optode: 3.5 mm Cannula: 4.3 mm |
Rat Neocortex | Electrode:+1.0 mm Optode: 0 mm | Electrode: 0.5 mm Optode: 3.0 mm | Electrode: 3.6 mm Optode: 1.5 mm |
Mouse Ventral Hippocampus | Electrode: −2.9 mm Optode: −1.6 mm | Electrode: 3.0 mm Optode: 2.0 mm | Electrode: 3.0 mm Optode: 1.8 mm |
