Seizures and Post-Ictal Respiratory Recovery in Kcnj16−/− Sprague-Dawley Rats
Authors: Zangl Luke , Bittencourt-Silva Paloma , Tabor Madeline , Lowe Moniece , Osmani Wasif , Forster Hubert , Hodges Matthew R. 
Published: May 2024

Epilepsy is a common neurological disorder (3.5 million in the US), of which ~1/3 continue to experience repeated seizures failing to benefit from anti-seizure medication. Poor seizure control puts patients with drug-resistant epilepsies at increased risk of Sudden Unexpected Death in Epilepsy (SUDEP), which is thought to result from severe post-ictal cardiorespiratory suppression. We’ve previously shown that Salt-Sensitive (SS) rats lacking 18 base pairs in the Kcnj16 gene (SS Kcnj16−/−), corresponding to a 6 amino acid (AA163-168) deletion in the second TM domain of Kir5.1, are susceptible to audiogenic seizures. Repeated seizures (1/day for 10 days) in this rat model resulted in ictal apnea, post-ictal respiratory suppression, diminished chemoreflexes, and high spontaneous mortality (PMID: 33232300). Here we generated additional Kcnj16−/− mutants on the outbred Sprague Dawley (SD Kcnj16−/−) genetic background to test the hypothesis that Kcnj16 mutations (T64I substitution; AA64-68 deletion (M7), and AA64-81 deletion (M8)) in the first TM domain of Kir5.1 causes: 1) audiogenic seizures, 2) progressive exacerbation of post-ictal ventilatory dysfunction, and 3) seizure-induced mortality. Ventilation (whole-body plethysmography) and seizure severity (Racine Score; HD video) were measured in male and female SD Kcnj16−/− rats for 20 minutes (min; baseline (BL)) before exposure to an auditory stimulus (2 min) and for 20 min of recovery. Mixed frequency white noise (WN) or a 10 kHz tone (85-95 dB) reproducibly elicited generalized tonic-clonic seizures (GTCSs) in all three SD mutants (T64I, M7, and M8). In SD Kcnj16−/− rats (T64I n=2, M7 n=3, M8 n=7, wild type n=2), 1 seizure/day for 10 days led to ictal apneas and transient post-ictal respiratory changes along with increases in body temperature (+1°C) following seizures, where breath frequency initially decreased (-25% of BL) before increasing (+40%) at 5 min post-stimulus and normalizing by 20 min. Tidal volume increased ~+80% from BL in the first 5 min and returned to BL by 20 min post-ictal. Minute ventilation was decreased (-10%) from BL within 1 min, increased to +60% by 5 minutes and returned to BL within 20 min post-stimulus. In contrast to previous SS Kcnj16−/− rat data, SD Kcnj16−/− rat post-ictal breathing patterns were unchanged across the 10-day seizure protocol, and we observed 100% survival. Our preliminary data suggests that Kcnj16 mutations at multiple sites can elicit the audiogenic seizure phenotype, but that SD Kcnj16−/− mutant rats appear resistant to repeated seizure-induced post-ictal ventilatory dysfunction and mortality — i.e. a potentially useful SUDEP-resistant model of repeated seizures. Funded by NIH HL122358. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.