[Effect of synaptic transmission blockade and hypoglycemia on neuron impulse activity in cultured rat hippocampal...

Spontaneous neuronal activity was studied in rat hippocampal cell cultures using patch clamp technique in cell-attached or loose-patch configuration. It was found that in spite of relatively low average frequency (1-2 Hz) of neuronal activity in the cell cultures, neurons often fire doublets or triplets of action potentials with interspike interval of 60 ms and less. Interspike interval histograms were substantially better fitted by double exponential decay functions than by single exponential ones. On average, estimated decay time constant for the fits were tau1 approximately 36, ms and tau2 approximately 1000 ms respectively. Spontaneous neuronal firing to a large extent depended on glutamatergic excitation and GABA(A)ergic inhibition: a blocker of AMPA/kainate receptor CNQX (10 microM) either substantially decreased or completely blocked spontaneous action potentials; a blocker of GABA(A) receptors bicuculine (10 microM) increased neuronal firing. Effect of glucose deprivation on action potential frequency was also studied. It was found that glucose deprivation reduces AP frequency to 25% of control. Taken together, these results support an idea that hypoglycaemia alters synaptic transmission in hippocampus.