S. Deurveilher et E. Hennevin, Lesions of the pedunculopontine tegmental nucleus reduce paradoxical sleep(PS) propensity: evidence from a short-term PS deprivation study in rats, EUR J NEURO, 13(10), 2001, pp. 1963-1976
Cholinergic neurons in the mesopontine tegmentum are thought to play a crit
ical role in the generation of paradoxical sleep (PS). However, no study ha
s yet examined whether lesions of these neurons cause deficits of PS in the
rat. We describe here the effects of lesions of the pedunculopontine tegme
ntal nucleus (PPT) on spontaneous PS and on PS propensity, expressed during
and after a short period of PS deprivation. Lesions were induced by bilate
ral injections of ibotenate. PS deprivation was performed manually by gentl
y waking rats each time they showed polygraphic signs of PS. Two weeks afte
r lesions, an 8-h baseline recording was performed; the following day, rats
were PS deprived for 6 h and polygraphic recordings were then continued fo
r 2 h, to examine recovery sleep. The same protocol was repeated 1 week lat
er. Compared with controls and with rats with limited PPT lesions, rats bea
ring > 60% NADPH-diaphorase-positive cell loss within the PPT showed unaffe
cted PS under baseline conditions. However, they made fewer attempts to ent
er PS during deprivation and they exhibited an attenuated rebound increase
in PS time after deprivation. The number of PS attempts and the magnitude o
f PS rebound were negatively correlated with the percent loss of diaphorase
-positive neurons within the PPT. Thus, PS propensity that accumulated as a
result of PS deprivation was reduced after extensive PPT lesions. In summa
ry, although spontaneous PS was found to be unaltered, the PS deprivation p
rocedure used in this study demonstrated the dysfunctioning of PS caused by
PPT lesions.