Chronic exercise changes the baseline properties of central monoaminergic systems, identified neurons and related behaviors

Physical exercise influences monoamine-dependent behaviors of mammals and some invertebrates. However, little is known about how a specific neuron adapts its biophysical properties to acute or repeated physical activity. Here we tested the hypothesis that central monoaminergic neurons develop a state of readiness for exercise by changing their baseline biophysical properties during regular training. In the mollusc Lymnaea stagnalis , acute and two-week daily two-hour exercise (crawling in low water) changed the baseline rate of respiration and locomotion. Consumption was activated by regular exercise, while growth rate decreased. Under both acute and baseline chronic conditions (one day after completion of training), the dopaminergic neuron that controls respiration was hyperpolarized, and dopamine levels in the brain were reduced. Two-hour rest after acute exercise abolished these effects. Serotonergic neurons that control locomotion were depolarized both in situ and after being completely isolated from the network under both acute and chronic conditions. Our findings suggest that regular exercise alters the baseline biophysical properties of central monoaminergic neurons, potentially through an anticipatory mechanism preparing the nervous system for subsequent exercise.