title: Activity of neurons in the rostral medulla of the halothane-anesthetized rat during withdrawal from noxious heat.
abstract: The physiological and pharmacological properties of two classes of putative nociceptive modulatory neurons have been extensively characterized in the rostral ventromedial medulla (RVM) of the barbiturate-anesthetized rat. 'On-cells' show a burst of activity, and 'off-cells' a sudden pause immediately preceding the occurrence of nocifensor reflexes. In the present study, we have characterized the reflex-related activity of RVM neurons in halothane-anesthetized rats to determine whether the properties of these neurons are dependent on barbiturate anesthesia. Both on- and off-cells were identified in this preparation. Repeated noxious stimulation was associated with a high level of ongoing activity in on-cells, and a low level in off-cells. These data thus demonstrate that the previously described reflex-related changes in RVM neuron activity are not specific to barbiturate-anesthetized preparations, and that a failure to demonstrate off-cells in some studies may result from these neurons being inactive following repeated testing with noxious stimuli.
authors.affiliation: Department of Neurology, University of California, San Francisco 94143-0114.
authors.forename: M M
authors.initials: MM
authors.lastname: Morgan
authors.forename: M M
authors.initials: MM
authors.lastname: Heinricher
mesh_terms: D000200:Action Potentials; D000768:Anesthesia, General; D000818:Animals; D001931:Brain Mapping; D006221:Halothane; D006358:Hot Temperature; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology* / Q000503:physiopathology; D009474:Neurons / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D011712:Pyramidal Tracts / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex; D013997:Time Factors
chemical_list: D006221:Halothane