Once the vesicle is in the inhibitory interneuron, its translocation is mediated by pH and temperature, specifically a low or acidic pH in the vesicle and standard physiological temperatures. Once the toxin has been translocated into the cytosol, chemical reduction of the disulfide bond to separate thiols occurs, mainly by the enzyme NADPH-thioredoxin reductase-thioredoxin. The light chain is then free to cleave the Gln76-Phe77 bond of synaptobrevin. Cleavage of synaptobrevin affects the stability of the SNARE core by restricting it from entering the low-energy conformation, which is the target for NSF binding. Synaptobrevin is an integral V-SNARE necessary for vesicle fusion to membranes. The final target of TeNT is the cleavage of synaptobrevin and, even in low doses, has the effect of interfering with exocytosis of neurotransmitters from inhibitory interneurons. The blockage of the neurotransmitters γ-aminobutyric acid (GABA) and glycine is the direct cause of the physiological effects that TeNT induces. GABA inhibits motor neurons, so by blocking GABA, tetanus toxin causes violent spastic paralysis. The action of the A-chain also stops the affected neurons from releasing excitatory transmitters, by degrading the protein synaptobrevin 2. The combined consequence is dangerous overactivity in the muscles from the smallest sensory stimuli, as the damping of motor reflexes is inhibited, leading to generalized contractions of the agonist and antagonist musculature, termed a "tetanic spasm".