Renshaw cells in the spinal cord provide recurrent inhibition to alpha motor neurons via which neurotransmitter, and what is the clinical relevance of this circuit?
- A GABA; benzodiazepines potentiate Renshaw cell activity, reducing spasticity in upper motor neuron lesions
- B Dopamine; Parkinson's disease reduces Renshaw cell activity, contributing to rigidity
- C Glycine; strychnine poisoning blocks Renshaw cell inhibition, causing tetanic spasms and hyperreflexia ✓
- D Acetylcholine; acetylcholinesterase inhibitors enhance recurrent inhibition to reduce muscle fatigue
Explanation
Renshaw cells are inhibitory interneurons in the anterior horn activated by axon collaterals of alpha motor neurons. They release glycine onto the same (and neighbouring) alpha motor neurons, creating negative feedback (recurrent inhibition) to prevent excessive or sustained motor neuron discharge. Strychnine is a glycine receptor antagonist; by blocking Renshaw cell-mediated glycinergic inhibition, it causes uninhibited motor neuron discharge resulting in tetanic convulsions and hyperreflexia — mimicking tetanus toxin which blocks glycine release presynaptically. This circuit is important for fine motor control and limiting overshoot of movements.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.