Exercise and sensory integration. Role of the nucleus tractus solitarius.

Since NTS neurons receive synaptic input from many sensory modalities, it is crucial to understand the neuronal mechanisms involved in synaptic processing. We have proposed that GABA-containing neurons in the NTS are the primary target for somatic afferent fibers activated by skeletal muscle contraction. In our model, local inhibition of baroreceptor signaling is necessary to counteract the increase in baroreceptor input such that NTS output is normalized and baroreflex sensitivity is maintained during exercise. This GABAergic mechanism, in conjunction with sympathoexcitation evoked by somatic afferents, preserves reflex sensitivity and resets the baroreflex, respectively. Unfortunately, there is insufficient data to date to support or refute the proposed role for GABA on baroreflex function during exercise. However, we feel that this model will be useful in formulating future experiments to explore these synaptic interactions.