Substantia nigra is known to highly express glibenclamide binding site, a protein associated to ATP-sensitive K^+ (K_(ATP)) channel in the brain. However, the functional expression of K_(ATP) channels in the area is not yet known. In this work, we attempted to estimate the functional expression of K_(ATP) channels in neurons of the substantia nigra pars compacta (SNC) in young rats using slice patch clamp technique. Membrane properties and whole cell currents attributable to K_(ATP) channel were examined by the current and voltage clamp method, respectively.
In SNC, two sub-populations of neurons were identified. Type I (rhythmic) neurons had low frequency rebound action potentials (4.5±0.25 ㎐, n = 75) with rhythmic pattern. Type II (phasic) neurons were characterized by faster firing (22.7±3.16 ㎐, n =12). Both time constants and membrane capacitance in rhythmic neurons (34.0±1.27 ㎳, 270.0±11.83 pF) and phasic neurons (23.7±4.16 ㎳, 184±35.2 pF) were also significantly different. The current density of K_(ATP) channels was 6.1±1.47 pA/pF (2.44∼15.43 pA/pF, n = 8) at rhythmic neurons of young rats.
Our data show that in SNC there are two types of neurons with different electrical properties and the density of K_(ATP), channel of rhythmic neuron is about 600 channels per neuron.
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