Tubocurarine and strychnine block Renshaw cell inhibition in the isolated mammalian spinal cord.

1. Stimulating a lumbar dorsal root (A) of an isolated mammalian spinal cord preparation sets up a reflex (DR-VR) in the corresponding ventral root (A) of that segment. 2. If an adjacent motor root (B) is antidromically stimulated 100 msec before the dorsal root A is stimulated, it inhibits the ventral root A response. (i.e. Renshaw cell inhibition of A through antidromic stimulation of recurrent collateral of B). 3. Stimulation of the lateral side of the spinal cord 5 mm rostral to the DR-VR reflex sets up a powerful inhibition of the reflex. 4. The inhibition is abolished by tubocurarine, or by strychnine indicating that the lateral stimulation is activating a cholinergic and a glycinergic pathway. 5. Addition of tubocurarine increases the steady "spontaneous" activity in the motor roots. 6. Addition of tubocurarine and 10(-3) M magnesium produces long lasting rhythmic bursting activity in the motor roots that persists even after 45 min of washing. 7. The isolated mammalian spinal cord preparation in addition to having active sensory, motor, and interneurones, has active Renshaw cells that can be studied using this preparation free from any blood-brain barrier and so are easily permeated by tubocurarine, etc.