Final answer:
The chemical that affects neural signaling without changing the resting potential is a neurotransmitter inhibitor, which influences neurotransmitter action at synapses without causing direct changes to the neuron's resting membrane potential.
Step-by-step explanation:
Chemical Agents Affecting Neurotransmission
Neurotransmitters are crucial for neural signaling as they carry chemical signals between neurons. When an action potential reaches a neuron's axon terminal, it depolarizes that area and causes voltage-gated Na+ channels to open. Subsequently, voltage-gated Ca2+ channels open, allowing Ca2+ to enter the neuron and initiate a cascade leading to the release of neurotransmitters into the synaptic cleft. These neurotransmitters may then bind to ligand-gated ion channels on the postsynaptic membrane, either initiating a new action potential or inhibiting one. The neurotransmitter inhibitor mentioned in the question refers to a chemical that affects signaling by interfering with neurotransmitter release or receptor binding without altering the neuron's resting potential directly.