1. The rat brain type IIA Nae channel a-subunit was stably expressed in Chinese hamster ovary (CHO) cells. Current through the expressed Na+ channels was studied using the whole-cell configuration of the patch clamp technique. The transient Na+ current was sensitive to TTX and showed a bell-shaped peak current vs. membrane potential relation. 2. Na+ current inactivation was better described by the sum of two exponentials in the potential range -30 to +40 mV, with a dominating fast component and a small slower component. 3. The steady-state inactivation, hoo, was related to potential by a Boltzmann distribution, underlying three states of the inactivation gate. 4. Recovery of the channels from inactivation at different potentials in the range -70 to -120 mV were characterized by an initial delay which decreased with hyperpolarization. The time course was well fitted by the sum of two exponentials. In this case the slower exponential was the major component, and both time constants decreased with hyperpolarization.5. For a working description of the Nae channel inactivation in this preparation, with a minimal deviation from the Hodgkin-Huxley model, a three-state scheme of the form O = II = I2 was proposed, replacing the original two-state scheme of the Hodgkin-Huxley model, and the rate constants are reported. 6. The instantaneous current-voltage relationship showed marked deviation from linearity and was satisfactorily fitted by the constant-field equation. 7. The time course of activation was described by an mx model. However, the best-fitted value of x varied with the membrane potential and had a mean value of 2. 8. Effective gating charge was determined to be 4-7e from the slope of the activation plot, plotted on a logarithmic scale. 9. The rate constants of activation, am and /3n were determined. Their functional dependence on the membrane potential was investigated.Neuronal excitability is mediated by ion-specific channel proteins through which membrane currents flow. The rising phase of the action potential is caused by an influx of Na+ ions through voltage-activated Na+ channels (Hille, 1992). The mammalian brain Na+ channel is a heterotrimeric protein consisting of a large glycosylated ax-subunit of 230-270 kDa and two smaller /31-and ,82-subunits (36 and 33 kDa, respectively). Different cDNA clones encoding highly homologous subtypes (types I, II, IIA, and III) of the a-subunit have been isolated from rat brain. The type II form is most predominant in embryonic and neonatal brain, whereas the alternatively spliced form of type II, i.e. type IIA, is most abundant in adult brain (Beckh, Noda, Liibbert & Numa, 1989). The cDNA for the rat brain Nae channel /31-subunit has also been cloned (Isom et al. 1992).The mRNA encoded by the Nae channel type IIA ac-subunit, when injected in Xenopus oocytes, directs the synthesis of functional Na+ channels, but with slower inactivation properties. Co-expression of the /31-subunit increases the expression level and accelerates the decay of Nae current (Catterall, 1992...

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Nature-inspired metaheuristic algorithms find near optimum solutions in a fast and efficient manner when used in a complex problem like finding optimum number of neurons in hidden layers of a multi-layer perceptron (MLP). In this chapter, a classification work is discussed of malignant melanoma, which is a type of lethal skin cancer. The classification accuracy is more than 91% with visually imperceptible features using MLP. The results found are comparably better than the related work found in the literature. Finally, the performance of two metaheuristic algorithms (i.e., particle swarm optimization [PSO] and simulated annealing [SA]) are compared and analyzed with different parameters to show their searching nature in the two-dimensional search space of hidden layer neurons.

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