Brain research
-
Kainic acid was injected bilaterally (4.8 micrograms in 1.2 microliters each side) into the dorsolateral pontomesencephalic tegmentum of cats in order to destroy the cholinergic neurons located in that region and thus to study the effects of their destruction upon sleep-waking states. The kainic acid produced a large area of nerve cell loss and/or gliosis centered in the dorsolateral tegmentum-cholinergic cell area, that includes the pedunculopontine tegmental (PPT) and laterodorsal tegmental (LDT) nuclei rostrally (A1-P2), and the parabrachial (PB) and locus coeruleus (LC) nuclei caudally (P3-P5). The mean loss of choline acetyltransferase (ChAT)-immunoreactive neurons within this area was 60% with a range from 25% to 85% across 11 cats. ⋯ The percent of PS-like epochs, the rate of PGO spiking and the EMG amplitude on postlesion day 28 were found to be significantly correlated with the volume of the lesion within the dorsolateral pontine tegmentum-cholinergic cell area. The percent PS-like episodes and PGO spike rate were significantly correlated with the number of remaining ChAT-immunoreactive neurons, but not with the number of remaining TH-immunoreactive neurons within this region. These results suggest that cholinergic pontomesencephalic neurons may be critically involved in the generation of paradoxical sleep and its phasic events.