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. Author manuscript; available in PMC: 2016 May 10.
Published in final edited form as: Int Rev Neurobiol. 2011;99:23–50. doi: 10.1016/B978-0-12-387003-2.00002-1

Figure 4. Model for how homeostatic regulation of BK channels contributes to both drug tolerance and withdrawal.

Figure 4

A) In a naïve, no drug state, neurons of the giant fiber pathway in Drosophila exhibit a basal capacity for repetitive firing when evoked by high frequency stimulation (Normal). B) The capacity for repetitive firing is significantly inhibited by exposure to sedative drugs (Sedation), leading to the overall depression of neural activity characteristic of sedation. C) Drug exposure induces expression of presynaptic BK channels as part of a homeostatic response to sedation. Increased BK channel activity enhances the capacity for repetitive firing, leading to a reduced effect of the anesthetic on neural firing during a subsequent exposure (Tolerance). D) After drug clearance, however, another effect of increased BK channel expression is unmasked, resulting in an enhanced neural excitability in the form of increased basal firing capacity and an increased susceptibility for seizures (Withdrawal). The electrophysiological traces shown here are schematic representations of hypothetical data, not real traces.