RESUMO
OBJECTIVE: Evidence from animal and human studies indicates that epilepsy can affect cardiac function, although the molecular basis of this remains poorly understood. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate pacemaker activity and modulate cellular excitability in the brain and heart, with altered expression and function associated with epilepsy and cardiomyopathies. Whether HCN expression is altered in the heart in association with epilepsy has not been investigated previously. We studied cardiac electrophysiologic properties and HCN channel subunit expression in rat models of genetic generalized epilepsy (Genetic Absence Epilepsy Rats from Strasbourg, GAERS) and acquired temporal lobe epilepsy (post-status epilepticus SE). We hypothesized that the development of epilepsy is associated with altered cardiac electrophysiologic function and altered cardiac HCN channel expression. METHODS: Electrocardiography studies were recorded in vivo in rats and in vitro in isolated hearts. Cardiac HCN channel messenger RNA (mRNA) and protein expression were measured using quantitative PCR and Western blotting respectively. RESULTS: Cardiac electrophysiology was significantly altered in adult GAERS, with slower heart rate, shorter QRS duration, longer QTc interval, and greater standard deviation of RR intervals compared to control rats. In the post-SE model, we observed similar interictal changes in several of these parameters, and we also observed consistent and striking bradycardia associated with the onset of ictal activity. Molecular analysis demonstrated significant reductions in cardiac HCN2 mRNA and protein expression in both models, providing a molecular correlate of these electrophysiologic abnormalities. SIGNIFICANCE: These results demonstrate that ion channelopathies and cardiac dysfunction can develop as a secondary consequence of chronic epilepsy, which may have relevance for the pathophysiology of cardiac dysfunction in patients with epilepsy.
Assuntos
Canalopatias/genética , Técnicas Eletrofisiológicas Cardíacas , Epilepsia Tipo Ausência/genética , Epilepsia do Lobo Temporal/genética , Frequência Cardíaca/fisiologia , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Canais de Potássio/genética , Animais , Canalopatias/fisiopatologia , Técnicas Eletrofisiológicas Cardíacas/métodos , Epilepsia Tipo Ausência/fisiopatologia , Epilepsia do Lobo Temporal/fisiopatologia , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/biossíntese , Masculino , Canais de Potássio/biossíntese , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Ratos , Ratos WistarRESUMO
The incidence of psychosis is increased in people with epilepsy, including idiopathic generalized epilepsies. To study the biological basis for this co-morbidity, we compared GAERS, a genetic rat model of absence epilepsy, to non-epileptic control rats (NEC). Mature, 14-week old GAERS showed enhanced amphetamine-induced locomotor hyperactivity - a feature also present in young (6-week old) GAERS prior to epilepsy onset. Prepulse inhibition and its disruption by psychotropic drugs did not differ between strains, although GAERS displayed elevated startle responses at both epileptic and pre-epileptic ages. The frontoparietal cortex of GAERS displayed a twofold increase in the power of gamma (30-80 Hz) oscillations, a proposed neurophysiological correlate of psychosis. Radioligand binding autoradiography demonstrated reduced densities of dopamine transporters in the caudate nucleus and nucleus accumbens core and of dopamine D2 receptors in the caudate nucleus. GAERS provide an opportunity to study the neurodevelopmental, genetic and therapeutic aspects of psychiatric comorbidities associated with epilepsy.