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. Author manuscript; available in PMC: 2013 Jul 1.
Published in final edited form as: Physiol Rev. 2012 Jul;92(3):1087–1187. doi: 10.1152/physrev.00032.2011

FIGURE 11.

FIGURE 11

Descending circuitry responsible for muscle atonia during REM sleep. During REM sleep, descending pontine subcoeruleus (SubC) glutamatergic projections excite diffusely organized glycinergic neurons of the bulbar reticular formation, including the medullary ventral gigantocellular nucleus (GiV). GABAergic/glycinergic output from the GiV inhibits spinal motoneurons, producing muscle atonia. An alternative pathway consists of a direct SubC glutamatergic projection to the spinal cord, directly synapsing on inhibitory interneurons of the ventral horn. When activated, these interneurons inhibit the spinal cord motor neurons, again producing muscle atonia. Red lines denote excitation; black, inhibition. [Adapted from Pakinos and Watson (989), with permission from Elsevier.]