A spinal interneuron integrates signals from two presynaptic inputs. One input has an excitatory effect via glutamate release, and the other has an inhibitory effect via glycine release. When the...

A spinal interneuron integrates signals from two presynaptic inputs. One input has an excitatory effect via glutamate release, and the other has an inhibitory effect via glycine release. When the excitatory presynaptic neuron fires alone, glutamate release leads to an action potential in the postsynaptic neuron. When both presynaptic neurons are fired simultaneously, the postsynaptic membrane is inhibited; it does not fire an action potential. How does glycine negate the otherwise excitatory effect of glutamate on this cell?

A. Glycine blocks glutamate release at the presynaptic membrane.

B. Glycine binds to glutamate, rendering it unable to bind to postsynaptic receptors.

C. Glycine competes with glutamate for the same receptors on the postsynaptic membrane.

D. Glycine binds to different receptors on the postsynaptic membrane, affecting ion channels.

E. Glycine activates the pump on the presynaptic membrane, which removes glutamate from the synaptic cleft.