Timing Mechanisms Underlying Gate Control by Feedforward Inhibition.
Level 5 - mechanism / opinion, no new human data
Bench and basic neurobiological laboratory research.
PubMed 30122375 · doi:10.1016/j.neuron.2018.07.026
What was done
Researchers investigated the cellular and biophysical timing mechanisms underlying spinal gate control, focusing on how disynaptic feedforward inhibition suppresses faster monosynaptic Aβ mechanoreceptor excitatory inputs to spinal pain transmission (T) neurons. The study evaluated glutamate receptor activation kinetics, potassium channel conductances (specifically I_A currents regulated by Preprodynorphin-expressing inhibitory neurons), and modulation by capsaicin-activated nociceptors.
What was found
The abstract reports no numerical values or sample sizes. Aβ-evoked, non-NMDA receptor-dependent EPSPs in T neurons were subthreshold, and action potential generation required slow-onset NMDA receptor activation. This delay provided the necessary temporal window for disynaptic inhibitory inputs to arrive and prevent firing. Constitutive I_A potassium currents either filtered out Aβ inputs or kept them subthreshold. Capsaicin-induced nociceptor activation reduced I_A, permitting Aβ inputs to drive action potential firing before inhibitory inputs arrived.
Why it matters
This work resolves a longstanding temporal paradox in Melzack and Wall's gate control theory by demonstrating how receptor kinetics and potassium channel filtering enable slower feedforward inhibition to successfully gate faster monosynaptic excitation.
Limits
The abstract contains no sample sizes, species details, or quantitative electrophysiological measurements. As a basic bench investigation, direct applicability to human clinical pain disorders remains to be established.
Cited by
- context Mechanoreceptors in the spine override and cancel out signals from nociceptors/pain receptors.