“…The function of these neurons in the modulation of nociception has been well established (Casey, 1971;Gebhart et al, 1983;Gray and Dostrovsky, 1983;Le Blanc and Gatipon, 1974). Neurons in this region are activated by peripheral noxious stimulation (Casey, 1971;LeBlanc and Gatipon, 1974), whereas stimulation of this area has been reported to alter nociceptive transmission (Basbaum and Fields, 1984;Clark and Proudfit, 1991;Fields and Basbaum, 1978;Satoh et al, 1983;Zhou and Gebhart, 1990). In addition, neurons in this medial portion of the rostral ventral medulla have been shown to respond to chemoreceptor input (Miura et al, 1996), project to medullary respiratory neurons, and innervate phrenic motor neurons, suggesting that these neurons are also involved in the regulation of respiration (Dobbins and Feldman, 1994;Ellenberger and Feldman, 1990;Ellenberger et al, 1992;Hadziefendic and Haxhiu, 1999;Holtman and Speck, 1994;Smith et al, 1989).…”