Figure 11.

REM sleep-like episodes of depression of XII nerve activity accompanied by the characteristic cortical and hippocampal activation can be elicited by microinjections of a cholinergic agonist, carbachol, into the dorsal mesopontine tegmentum in urethane-anesthetized, paralyzed, and artificially ventilated rats. (A) Typical REM sleep-like episode. The moving average of XII nerve activity (top) shows inspiratory bursts of activity. The amplitude of the bursts is reduced and the central respiratory rate declines within less than 2 min following pontine carbachol injection (at arrow). Parallel to the depression of XII nerve activity, there is cortical and hippocampal activation. The second trace from top shows raw signal recorded from the hippocampus. The third trace from top shows the power of hippocampal activity in the 3 to 5 Hz frequency band, which represents theta-like rhythm under urethane anesthesia. The increase in power of cortical EEG in the 6 to 9 Hz frequency band (bottom) indicates activation relative to the period prior to carbachol injection. The entire episode lasts about 5 min, after which all signals return to their precarbachol levels and patterns. The ability to repeatedly elicit such REM sleep-like episodes allows one to investigate cellular, neurochemical, and network mechanisms of the interaction between REM sleep and the regulation of breathing and upper airway muscle activity. (Unpublished record from the study described in Ref. 142.) B: The sites at which carbachol microinjections elicit REM sleep-like episodes in urethane-anesthetized rats superimposed onto two standard cross sections of the brainstem from levels 8.3 mm and 8.72 mm caudal to bregma. Abbreviations: LDN, laterodorsal tegmental nucleus; PPN, pedunculopontine tegmental nucleus; scp, superior cerebellar peduncle; VT, ventral tegmental nucleus. (Modified from Fig. 2 in Ref. 272 and republished with permission from Elsevier.)