Ligand-regulated and voltage-gated K channels

Voltage-gated K+ channels are critical to transmembrane potential- and Ca2+-mediated signalling. Voltage-regulated K+ channels are critically involved in action potentials as described above and such channels are blocked by the legume quinolizidine alkaloid sparteine (lupinidine) as well as by various synthetic psychoactive compounds with disparate effects such as amitryptiline, chlorpromazine, imipramine and phencyclidine. 

While some K+ channels are voltage-gated, others are modulated by G proteins (that are in turn regulated by particular hormones such as dopamine or adenosine) (see Chapter 5) and others are subject to Ca2+-dependent activation. A Ca2+-dependent K+ channel is opened by the lignan nordihydroguaiaretic acid (NDGA). 

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