Motor Neurons and Drugs

pediagenosis    June 15, 2021    Medicine , Pharmacology    Comment   

Motor Neurons and Drugs

Skeletal muscle spasticity often results from neuronal, not muscle, deficits. The reflex arc involved in coordinated skeletal muscle action involves several neurons, including interneurons, in the spinal cord. These spinal polysynaptic reflex arcs are depressed by a number of drugs, including barbiturates. However, nonspecific depression of synapses is not desirable because normal muscle function can be disrupted. 

More specific agents, including CNS­acting drugs, are preferred. Benzodiazepines allosterically facilitate GABA­mediated Cl⁻ influx (Figure 3­9) throughout the CNS, including the spinal cord. They are used for muscle spasm of almost any cause but can also produce excess sedation. Baclofen is a GABA_B receptor agonist that hyperpolarizes neurons by increasing K⁺ conductance. Other CNS­acting antispasmodic agents include α₂­adrenoceptor agonists (eg, tizanidine), GABA_A and GABA_B receptor agonists, and the inhibitory amino acid Gly.