Baclofen also inhibits neural function presynaptically, by reducing calcium ion influx, and thereby reducing the release of excitatory neurotransmitters in both the brain and spinal cord.
It may also reduce pain in patients by inhibiting the release of substance P in the spinal cord, as well.
Both of these classes of neuromuscular blocking drugs are structurally similar to acetylcholine, the endogenous ligand, in many cases containing two acetylcholine molecules linked end-to-end by a rigid carbon ring system, as in pancuronium (a nondepolarizing agent).
A view of the spinal cord and skeletal muscle showing the action of various muscle relaxants – black lines ending in arrow heads represent chemicals or actions that enhance the target of the lines, blue lines ending in squares represent chemicals or actions that inhibition the target of the line The generation of the neuronal signals in motor neurons that cause muscle contractions are dependent on the balance of synaptic excitation and inhibition the motor neuron receives.
Most neuromuscular blockers function by blocking transmission at the end plate of the neuromuscular junction.
Normally, a nerve impulse arrives at the motor nerve terminal, initiating an influx of calcium ions, which causes the exocytosis of synaptic vesicles containing acetylcholine.
This poison, known today as curare, led to some of the earliest scientific studies in pharmacology.
Its active ingredient, tubocurarine, as well as many synthetic derivatives, played a significant role in scientific experiments to determine the function of acetylcholine in neuromuscular transmission.
Muscle relaxation and paralysis can theoretically occur by interrupting function at several sites, including the central nervous system, myelinated somatic nerves, unmyelinated motor nerve terminals, nicotinic acetylcholine receptors, the motor end plate, and the muscle membrane or contractile apparatus.While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxants, The earliest known use of muscle relaxant drugs was by natives of the Amazon Basin in South America who used poison-tipped arrows that produced death by skeletal muscle paralysis.This was first documented in the 16th century, when European explorers encountered it.Several of these agents also have abuse potential, and their prescription is strictly controlled.receptors in the brain and spinal cord, resulting in hyperpolarization of neurons expressing this receptor, most likely due to increased potassium ion conductance.