Fig. 1.  Schematic representation of the potential sites of analgesic action of nicotine. In the central nervous system, there is widespread distribution of homomeric α7 and heteromeric α4β2* nicotinic acethylcholine receptors (nAChR), including regions associated with pain transmission such as the dorsal horn, locus ceruleus, and thalamus. The α9α10 nAChR is present in dorsal root ganglia. Many anesthetics also modulate or inhibit nAChR function. Activation of supraspinal and spinal nAChR results in opioid and norepinephrine (NEpi) release, which can reduce descending facilitatory pain pathways (green ) and enhance descending inhibitory pain pathways (red ), resulting in reduced transmission of nociceptive input (blue ).