The attenuating effects of exercise on the initial forced swimming-induced molecular responses in the Wnt inhibitor dentate gyrus may correspond with the reduced state of anxiety in exercising animals. The change in emotionality in these animals may be the result of adjustments in the GABAergic system. We had published that, besides distinct changes in the expression of GABA-A
receptor subunits (e.g. the extra-synaptic receptor associated delta and alpha-5 subunits), regular physical activity led to increased gene transcription of the GABA-synthesizing enzyme GAD67 (Hill et al., 2010). Moreover, our recent preliminary data indicate that GABA synthesis is increased in the dentate gyrus/CA3 of exercising rats (Kersanté et al., unpublished observations). This is an important observation as we have previously reported that GABAergic neurotransmission
is a critical regulator of stress-evoked (pERK1/2- and pMSK1/2-targeted) epigenetic and IEG transcriptional responses in the dentate gyrus (Papadopoulos et al., 2008). We found that a single injection of a non-sedative dose of the anxiolytic benzodiazepine, Lorazepam (a GABA-A receptor allosteric modulator) blocked the novelty stress-induced SB203580 rise in H3S10p-K14ac- and c-Fos-positive granule neurons in the dentate gyrus. Moreover, administration of the partial inverse agonist FG7142 resulted in strongly enhanced novelty-induced increases in H3S10p-K14ac-
and c-Fos-positive neurons in the dentate gyrus (Papadopoulos et al., 2008). FG7142 has been shown to be an anxiogenic drug in rats and humans by lowering GABA-A receptor function (Dorow et al., 1983, Kalueff and Nutt, 1996 and Evans and Lowry, 2007). Additional information on the not role of anxiety state and GABAergic neurotransmission on epigenetic, gene transcriptional and behavioral responses can be found elsewhere (Reul, 2014). Collectively, it seems that the beneficial effects of regular physical exercise on anxiety state and behavioral responses involve the enhancement of GABAergic inhibitory control. Thus, in addition to glucocorticoids, GABA may be an important mediator of the positive effects of exercise on resilience. Studies on the effects of regular exercise (and physical activity in general) on mood and affect in humans have been conducted over the past 20 years. The outcome picture has been rather mixed. For instance, some studies have been published showing improvements in measures of anxiety and depression (Steptoe et al., 1989, Byrne and Byrne, 1993 and Salmon, 2001) whereas an investigation looking into the effects of ‘facilitated physical activity’ in addition to usual care (antidepressant treatment) reported no significant effects (Chalder et al., 2012).