Anesthesia/anesthetics phenomena

It thus follows that the membrane concentration of typical P-gp substrates for halfmaximum activation of P-gp falls in the range of 1 to 10 mmole drug per mole lipid. This is a much narrower concentration range than that required for the same substances in the aqueous phase 10 8 to 10 3 M. A similar phenomenon has been observed in anesthesia. The membrane concentration of anesthetics required for anesthesia has been found to be 33 mM, independent of the anesthetic applied (Meyer-Overton rule). 

This simple quatrain wonderfully epitomizes the essence of the human mind. Awareness of one s inner and outer environments is central to the functioning of the human mind. Consciousness is the enigmatic phenomenon that is crucial to the interface between brain and mind. General anesthetics are drugs that temporarily rob us of our consciousness GABA is a key molecular target for general anesthesia. 

The exact reason for the differential susceptibility of nerve fibers based on their axonal diameter is not known. One possible explanation is that the anesthetic is able to affect a critical length of the axon more quickly in unmyelinated fibers, or small myelinated neurons with nodes of Ranvier that are spaced closely together compared to larger fibers where the nodes are farther apart.17 As indicated earlier, a specific length of the axon must be affected by the anesthetic so that action potentials cannot be transmitted past the point of blockade. Other factors such as the firing rate of each axon or the position of the axon in the nerve bundle (e.g., in the outer part of the bundle versus buried toward the center of the nerve) may also affect susceptibility to local anesthesia.62 In any event, from a clinical perspective the smaller-diameter fibers appear to be affected first, although the exact reasons for this phenomenon remain to be determined. 

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