Final answer:
Bupivacaine is generally recognized as the least vasodilating of the local anesthetics listed, with its ability to block voltage-gated sodium channels, thereby inhibiting neural transmission of pain signals and causing numbness in the applied area.
Step-by-step explanation:
Among local anesthetics like lidocaine, mepivacaine, bupivacaine, and articaine, lidocaine is typically considered to have a moderate vasodilating effect, but when comparing these options, bupivacaine is generally recognized as the least vasodilating.
Local anesthetics achieve their effect by blocking voltage-gated sodium channels on neuronal membranes, which normally enable the rapid influx of sodium ions during the initiation of an action potential. By doing so, they prevent the neuron from reaching the threshold potential necessary to trigger an action potential. This interruption in neural transmission effectively prevents the sensation of pain and the perception of other sensory input, leading to numbness in the region where the anesthetic is applied.