Kcnj16 (Kir5.1) Mutations in Sprague Dawley Rats: Characteristics of SUDEP-Resistant Rat Models of Repeated Seizures

Epilepsy is one of the most common neurological disorders, and current anti-seizure medications fail to prevent seizures in ~1/3 of patients. Patients with uncontrolled seizures are at increased risk of Sudden Unexpected Death in Epilepsy (SUDEP), which is postulated to result from severe post-seizure cardiorespiratory (CR) suppression. We have previously characterized the effects of repeated seizures in the Salt-sensitive Kcnj16 ^-/- rat (SS ^Kcnj16-/- ) model, in which repeated daily seizures led to a progressive post-seizure respiratory suppression and high seizure-related mortality. Associated with these phenotypes were decreased immunoreactivity (IR) for serotonergic (5-HT) system markers, increased microglia and inflammatory molecules within key brainstem CR nuclei. Here we test the hypothesis that mutations of Kcnj16 (corresponding to amino acid (AA) T64I substitution, AA64-68 deletion (M7), and AA64-81 deletion (M8)) on the Sprague Dawley (SD ^Kcnj16-/- ) genetic background will also show audiogenic seizures, along with progressive post-ictal ventilatory dysfunction, spontaneous mortality, and brainstem CR nuclei with disturbed serotonergic signaling capacity and increased inflammation. To test this hypothesis, ventilation (whole-body plethysmography) and seizure severity (Racine Score; HD video) were measured in male and female SD ^Kcnj16-/- and wild type (WT) rats for 20 min before (baseline (BL)) and after a 2 min seizure-inducing auditory stimulus applied once daily for 10 days. Similar to SS ^Kcnj16-/- rats, sound stimuli reliably caused generalized tonic-clonic seizures in all SD mutants (T64I; n=15, M7; n=10, and M8; n=12). Seizures also led to ictal apneas (~8 seconds), transient decreases in breathing frequency (-20% from BL), and increased tidal volume (+80% from BL) within 5 minutes before returning to BL within 20 minutes. In contrast to SS ^Kcnj16-/- rats, all SD ^Kcnj16-/- rats had an overall stimulation of total ventilation (+175% from BL) at 5 minutes post-seizure, returning to BL within 20 minutes. Importantly, there was no seizure-related mortality in all SD ^Kcnj16-/- rat lines. After 10 days of repeated seizures, SD ^Kcnj16-/- (n=2) and WT (n=2) brainstems were perfusion fixed, harvested, flash frozen, and cryosectioned (20 μm) for staining. Unlike SS ^Kcnj16-/- rats, we observed no obvious changes in markers of the 5-HT system or CNS immune cells within medullary CR nuclei. Thus, although mutations of Kcnj16 led to audiogenic seizures in SD ^Kcnj16-/- mutants, these rat lines appear resistant to progressive post-ictal ventilatory dysfunction and mortality suggesting genetic background influences mechanisms of seizure-induced death.

Funded by NIH HL122358.

This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.