Influence of wheel running on seizure modulation and galanin gene expression in the rat locus coeruleus

Abstract

Voluntary wheel running is associated with a reduction in seizure severity, an effect that in part arises from the activity of galanin, an inhibitory neuropeptide whose gene expression in the locus coeruleus is sensitive to exercise. The effect of three weeks of free access to activity wheels on the severity of kainic acid-induced seizures was investigated. Associated measures of seizure severity, a modified Racine severity scale and frequency of spike-wave discharges with electroencephalography, were used to characterize seizure severity at a i.p. dose of 10mg/kg of kainic acid. The difference in spike-wave frequency approached significance between exercising and sedentary rats. To investigate the influence that aerobic capacity may have on any exercise-induced upregulation of galanin in the locus coeruleus, rats selectively bred to demonstrate greater or lesser aerobic capacity, and Sprague-Dawley rats, were provided with free access to activity wheels for three weeks. Galanin and tyrosine hydroxylase gene expression in the locus coeruleus was quantified using in situ hybridization and optical density analysis. The different strains of rats did run differently over the study, and both strain and exercise condition did affect galanin mRNA expression, but did not influence tyrosine hydroxylase gene expression. No strain differences in galanin or tyrosine hydroxylase expression was observed in sedentary rats. Galanin expression and overall running distance were significantly correlated. This data demonstrates that exercise-induced galanin upregulation is related only to the amount of running, and that the capacity to run does not have any additional influence.