Plasma melatonin concentration and the immobility time in FST on day 35.

<p>The total production of melatonin in taVNS treated rats may be higher since the melatonin concentrations were still higher upon sacrifice on day 35, about 22 hours after the last taVNS session on day 34. This may represent the long term effect of taVNS on melatonin secretion (A). In the forced swimming session, a longer immobility time exists in naïve ZDF rats, in contrast to that in taVNS treated ZDF rats or naïve ZL rats (B). *, **, *** <i>P</i><0.05, 0.01, 0.001 <i>vs.</i> ZDF, respectively.