Scorpion venom mostly affects neuronal firing activity by inhibiting recovery.
There are some 100 subtypes of K+ channels and some 120 different scorpion toxins known. Of this host of toxins, the majority were tested on
Shaker-related channels (subfamily KV1.x). Some peptides were shown to act on the Ca2+-activated K+ channels (KCa1.1, KCa3.1, KCa2.x. The family of so-called g-KTx toxins is specific for the ether-a-go-go family of K+ channels (KV11.x) (Rodriguez de la Vega & Possani, 2004).
The Shaker subfamily and the ether-a-go-go family are all voltage-gated channels and hence closely involved in action potential generation (Coleman et al., 1999; Shepard et al., 2007)]; the Ca2+-activated K+ channels are activated when Ca2+ enters the cell, which is an event typically associated with action potentials too.
Hence, based on this information I conclude that scorpion venom mainly blocks the repolarization phase of neurons, meaning the maximum firing rate will be drastically reduced because recovery is blocked. Neurons can fire, but they will not be able to recover from continuous firing.
Scorpion venom is not strongly associated with potassium leak channels (KCNK family). Although other families may also affect the resting membrane potential, it is the KNCK family that is mostly associated with generating the cell resting membrane potential (Cohen et al., 2009). hence, scorpion venom will not affect the resting membrane potential too much.
- Coleman et al., J Neurochem (1999); 73: 849–58
- Rodriguez de la Vega & Possani, Toxicon (2004); 43: 865–875
- Shepard et al., Schizophrenia Bulletin; 33(6): 1263–9
- Cohen et al., Eur Biophys J (2009); 39(1): 61-73