The dorsal horn of the spinal cord contains many transmitters and receptors involving in pain transmission and modulation. Monoamines and g -aminobutyric acid (GABA) play a key role in the modulation at level of dorsal horn (DH) of the spinal cord, the site of primary processing of afferent nociceptive information. Agents that enhance the action of GABA at the GABAA receptors can produce antinociception. For example intrathecal administration of benzodiazepines increases pain threshold in various models of pain. There is also substantial evidence for robust antinociceptive properties of spinal administration of clonidine and other a2-agonists.

        Key words: dorsal horn, pain transmission, GABA, a2 -agonist, clonidine, benzodiazepines