Glucose sensitivity in mouse substantia nigra pars reticulata neurons in vitro

Glucose sensitivity of substantia nigra pars reticulata (SNr) GABAergic neurons was investigated by extracellular recording in acute slice. Approximately two thirds of the GABAergic SNr neurons tested exhibited a significant increase in spontaneous firing rate as the extracellular glucose concentration was lowered from 10 to 4-6 mM. At lower glucose concentrations, a small proportion of these glucose-sensitive GABAergic SNr neurons exhibited multiple, robust increases in spontaneous firing rate with periods ranging in minutes. Similar changes in firing rate of SNr neurons in response to lowered glucose were detected under blockade of GABAA, NMDA, and non-NMDA receptors, indicating that mechanisms other than those mediated by the major synaptic transmissions in the SNr are involved. These findings suggest involvement of previously unknown glucose dependent alterations of GABAergic SNr neuronal activity in the central regulation of glucose homeostasis.