Spider venom peptide Pn3a inhibits ~55% of pain neuron calcium currents and works additively with sub-therapeutic opioids, explaining its pain relief at doses far above its Nav1.7 potency.
55% calcium current blockedPn3a inhibited over half of high-voltage calcium currents in pain-sensing DRG neurons
What the researchers found
Pn3a inhibits ~55% of DRG HVA calcium currents and 60-80% of Cav1.2/1.3/2.1/2.2 channels; shows additive inhibition with sub-therapeutic opioids on shared calcium channel targets.
Why it matters
Understanding how spider venom peptides interact with opioid pathways could enable new pain treatments using low-dose opioid combinations — reducing addiction risk while maintaining pain relief.
The numbers in context
10 uM Pn3a: ~55% HVA-ICa block; 60-80% Cav1.2/1.3/2.1/2.2 inhibition; Cav2.2 IC50=3.71 uM; 18mV hyperpolarizing inactivation shift; enhanced with DAMGO; no Cav2.3 effect
How the study worked
Whole-cell patch clamp electrophysiology in rat DRG neurons and HEK293 cells expressing individual Cav channels; IC50 determination for Cav2.2; voltage-dependence characterization; opioid co-application experiments.
Who was studied
Rat dorsal root ganglion neurons and HEK293 cells expressing Cav1.2, 1.3, 2.1, 2.2, and 2.3 channels
What this study cannot tell us
In vitro electrophysiology only; Pn3a concentrations needed are high (µM range); selectivity concerns with blocking multiple Cav channels; no in vivo pain model data in this study.
How to read the evidence
Moderate — rigorous electrophysiology study with clear mechanistic insights, but in vitro only.
When this study was published
Published in 2020; venom-derived analgesic peptides are an active drug development area.
The bigger picture
The opioid crisis demands new pain strategies. Venom peptides that enhance low-dose opioid effects could enable effective pain relief with dramatically reduced opioid doses and addiction risk.
Questions still open
- Could Pn3a-like peptides enable opioid dose reduction in clinical pain management?
- Are there more selective Cav2.2 inhibitors from spider venoms?
- What are the cardiovascular risks of blocking Cav1.2 (cardiac calcium channel)?
Common questions
How could spider venom help with pain?
Why combine with opioids?
Read the original research
Spider Venom Peptide Pn3a Inhibition of Primary Afferent High Voltage-Activated Calcium Channels.
Frontiers in pharmacology, 11, 633679
Citation
McArthur, Jeffrey R; Munasinghe, Nehan R; Finol-Urdaneta, Rocio K; Adams, David J; Christie, Macdonald J. (2020). Spider Venom Peptide Pn3a Inhibition of Primary Afferent High Voltage-Activated Calcium Channels.. Frontiers in pharmacology, 11, 633679. https://doi.org/10.3389/fphar.2020.633679