Abstract
Midbrain substantia nigra pars reticulata (SNr) is the major output nucleus of basal ganglia, which is important for motor regulation. SNr consists mostly of GABAergic neurons, of which spontaneous firing rate is among highest in the brain, implying that demand for energy sources such as oxygen and glucose is very high. Indeed, we have previously shown that SNr activity is extremely sensitive to hypoxic conditions and under severe hypoxia SNr activity is suppressed quickly, resulting in protection against seizure propagation. In contrast, moderate lowering of extracellular glucose concentration in acute slice facilitates SNr activity. A similar sensitivity for lowering glucose was originally found in lateral hypothalamus, but the underlying mechanism is still uncertain. Here we show by using acutely dissociated SNr neurons that the glucose sensitivity is produced via post-synaptic mechanisms. We also found that dopamine, glycine, and insulin had modulatory effects on SNr activity in addition to well established neurotransmitters in the SNr, GABA and excitatory amino acid. Evidence has accumulated showing that increased SNr activity inhibits locomotion and REM, and is related to rhythmical movements such as of the jaw and limb. Thus, SNr neurons may have a role as fuel sensors which inform energy status for coordinating motor activity and for protecting brain in emergency, and various neuromodulators can regulate the sensor property. [J Physiol Sci. 2007;57 Suppl:S147]
