TY - JOUR
T1 - Nocifensive reflex-related on- and off-cells in the pedunculopontine tegmental nucleus, cuneiform nucleus, and lateral dorsal tegmental nucleus
AU - Carlson, Jonathan Dennis
AU - Selden, Nathan Richard
AU - Heinricher, Mary Magdalen
N1 - Funding Information:
We appreciate the technical assistance of Miranda Neubert and Melissa Martensen. This research was supported in part by grants from NIH: DA 05608 (MH), NS 044255 (NS), and a Tarter Fellowship (JDC).
PY - 2005/11/30
Y1 - 2005/11/30
N2 - Cholinergic projections from the pedunculopontine tegmental nucleus (PPTg) to the rostral ventromedial medulla (RVM) have been implicated in nociceptive modulation. The goal of this study was to identify neurons with nocifensive reflex-related activity in the mesopontine tegmentum including the PPTg. This study used the same behavioral neurophysiological classification system to identify neurons as has been extensively described in the RVM. Extracellular microelectrode recording was conducted in lightly anesthetized rats. Changes in firing associated with the noxious heat-evoked tail flick reflex were used to classify neurons as "on-cells" (displayed a burst in neuronal activity associated with the reflex), "off-cells" (displayed a pause in activity), and neutral cells (showed no response). Of 188 neurons studied in 23 rats, 77 were classified as on-cells, 14 as off-cells, the remainder as neutral cells. Recordings during periods without noxious stimulation found that some of the on- and off-cells displayed spontaneous transitions between active and silent periods termed cell cycling. The distribution of on- and off-cells in the mesopontine tegmentum overlapped and included the cholinergic PPTg and lateral dorsal tegmental nucleus identified by NADPH diaphorase staining, as well as the cuneiform nucleus and periaqueductal gray. The mesopontine tegmentum thus contains nocifensive reflex-related neurons with neurophysiological characteristics similar to those reported in the RVM. Neurons showing reflex-related activity were frequently encountered in the cholinergic PPTg and LDTg. Further studies will be required to determine whether these neurons modulate nociception through a link to the RVM.
AB - Cholinergic projections from the pedunculopontine tegmental nucleus (PPTg) to the rostral ventromedial medulla (RVM) have been implicated in nociceptive modulation. The goal of this study was to identify neurons with nocifensive reflex-related activity in the mesopontine tegmentum including the PPTg. This study used the same behavioral neurophysiological classification system to identify neurons as has been extensively described in the RVM. Extracellular microelectrode recording was conducted in lightly anesthetized rats. Changes in firing associated with the noxious heat-evoked tail flick reflex were used to classify neurons as "on-cells" (displayed a burst in neuronal activity associated with the reflex), "off-cells" (displayed a pause in activity), and neutral cells (showed no response). Of 188 neurons studied in 23 rats, 77 were classified as on-cells, 14 as off-cells, the remainder as neutral cells. Recordings during periods without noxious stimulation found that some of the on- and off-cells displayed spontaneous transitions between active and silent periods termed cell cycling. The distribution of on- and off-cells in the mesopontine tegmentum overlapped and included the cholinergic PPTg and lateral dorsal tegmental nucleus identified by NADPH diaphorase staining, as well as the cuneiform nucleus and periaqueductal gray. The mesopontine tegmentum thus contains nocifensive reflex-related neurons with neurophysiological characteristics similar to those reported in the RVM. Neurons showing reflex-related activity were frequently encountered in the cholinergic PPTg and LDTg. Further studies will be required to determine whether these neurons modulate nociception through a link to the RVM.
KW - Acetylcholine
KW - Nociception
KW - Rostral ventromedial medulla
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U2 - 10.1016/j.brainres.2005.09.036
DO - 10.1016/j.brainres.2005.09.036
M3 - Article
C2 - 16256081
AN - SCOPUS:28444493646
SN - 0006-8993
VL - 1063
SP - 187
EP - 194
JO - Brain research
JF - Brain research
IS - 2
ER -