Effects of Hexasulfobutylated C60 on the Thalamic Neurons in Neonatal Rat in vitro

The effects of hexasulfobutylated C₆₀ (FC₄S) on membrane potentials and currents were studied by tight-seal, whole-cell recording in thin slices of the neonatal rat thalamus. Silent neuron with resting membrane potentials of around -62.4 ± 0.7 mV was found in whole-cell current clamp recordings. Hexasulfobutylated C₆₀ depolarized the neuron by a concentration dependent manner. It also (1) prolonged the decay time constant of action potential and (2) decreased the threshold of the directly elicited action potentials of the neuron. Hexasulfobutylated C₆₀ did not alter the input resistance of the excitable membrane. In whole-cell voltage clamp studies, depolarizing command pulses from a holding potential of about -70 mV evoked a fast inward current followed by an outward current in the thalamic neurons. Hexasulfobutylated C₆₀ (30 - 100 μM) increased the total inward sodium current of the neuron, while hexasulfobutylated C₆₀ did not alter the outward potassium currents in all voltage steps tested. It was concluded that hexasulfobutylated C₆₀ (1) decreased the threshold of the action potential and (2) prolonged the decay time constant of the directly elicited action potential of the neonatal rat thalamic neurons. The effect may be closely associated with the Na⁺ current in thalamic neurons.