Location and spike-train characteristics of cells in anterodorsal pons having selective decreases in firing rate during desynchronized sleep.
Extracellular microelectrode recordings were made from single neurons in the pontomesencephalic brain stem of head-restrained but nonanesthetized cats whose behavioral state was continuously monitored polygraphically. A population of neurons was encountered with the unusual property of progressively decreasing discharge rate as the cats passed from waking (W) through synchronized sleep (S) to desynchronized sleep (D). In many cases there was a complete cessation of firing in desynchronized sleep, suggesting the designation D-off cell for this neuronal subtype. The D-off cell population was distributed in a bandlike zone across the brain stem at the pontomesencephalic junction with dense concentration of cells in aminergic nuclei: the serotonergic dorsal raphe and raphe linearis centralis and noradrenergic locus ceruleus and peribrachial regions. Aside from a sparse distribution in the central tegmental field, there were no D-off cells in pontine reticular nuclei where cells of the D-on type abound. The proportion of cells showing the D-off property and the magnitude of the state-related change were correlated across nuclear groups as follows: raphe and peribrachial (highest), locus ceruleus (intermediate), and reticular (lowest) for both values. The firing rates of D-off cells tended to be low in waking with very regular interspike intervals. This characteristic firing pattern and the anatomical distribution suggests that D-off cells may be tentatively identified as aminergic. The marked contrasts in aminergic neuronal activity between waking and desynchronized sleep are interpreted as possibly playing a role in state generation through progressive distribution of cholinergic neurons postsynaptic to the D-off cell population. Predictable results would not only be a change in the excitability of the postsynaptic population but also a change in response mode related to a shift in neurotransmitter throughout the brain.
D000200:Action Potentials; D000818:Animals; D002415:Cats; D008125:Locus Coeruleus / Q000166:cytology; D008297:Male; D009474:Neurons / Q000502:physiology*; D011149:Pons / Q000166:cytology / Q000502:physiology*; D011903:Raphe Nuclei / Q000166:cytology; D012154:Reticular Formation / Q000166:cytology; D012890:Sleep / Q000502:physiology*