even persist after the removal of the stimulus. Two distinct types of mechanosensitive ion channels have been found in the posterior root ganglion neurons. The two channels are broadly classified as either high-threshold (HT) or low threshold (LT). As their names suggest, they have different thresholds as well as different sensitivities to pressure. These are cationic channels whose activity appears to be regulated by the proper functioning of the cytoskeleton and cytoskeleton associated proteins. The presence of these channels in the posterior root ganglion gives reason to believe that other sensory neurons may contain them as well. High-threshold mechanosensitive channels High-threshold channels have a possible role in nociception. These channels are found predominantly in smaller sensory neurons in the dorsal root ganglion cells and are activated by higher pressures, two attributes that are characteristic of nociceptors. Also, the threshold of HT channels was lowered in the presence of PGE2 (a compound that sensitizes neurons to mechanical stimuli and mechanical hyperalgesia) which further supports a role for HT channels in the transduction of mechanical stimuli into nociceptive neuronal signals. Presynaptic control The presynaptic regulation of the dorsal nerve ending discharge in the spinal cord can occur through certain types of GABAA receptors but not through the activation of glycine receptors which are absent from these types of terminals. Thus GABAA receptors but not glycine receptors can presynaptically control nociception and pain transmission. See also Anterior root of spinal nerve Knee jerk References Additional images External links Photo of model at Ohio State University Diagram at webanatomy.net Photo at uwlax.edu Back anatomy Peripheral nervous system