Systems neuroscienceGABAergic processes in the mesencephalic tegmentum modulate the occurrence of active (rapid eye movement) sleep in guinea pigs
Section snippets
Experimental procedures
Adult male guinea pigs (Cavia porcellus) weighing between 450 and 550 g were used in the present study. All experimental procedures were approved by the Commission for Animal Experimentation of the Universidad de la República of Uruguay and were in accordance with the Guide for the Care and Use of Laboratory Animals (7th edition, National Academy Press, Washington, DC, 1996). All efforts were made to minimize the number of animals used in this study, and adequate measures were taken to minimize
Control experiments
Quiet W was the predominant state of the animals after they had been adapted to the recording conditions; this state was interrupted occasionally by brief episodes of sleep. Examples of typical polygraphic recordings obtained under control conditions are shown in Fig. 1A. This figure illustrates the spontaneous presence of naturally-occurring states of W, QS and AS; it should be noted, because this is a characteristic of sleep in these animals that at the beginning of AS there is an incomplete
Discussion
In the present study we demonstrate that the inhibition, by GABAA agonists, in the vlPAG and the adjacent dMRF of the guinea pig, produces AS hypersomnia. This effect is blocked by the GABAA antagonist bicuculline. In addition, collateral effects such as hypotonia/atonia and cortical waking-spindles were present during some of these experiments.
The present study was performed in guinea pigs, as a part of a global research program designed to explore the mechanisms of W and sleep in guinea pigs (
Conclusion
The present report represents a foundation for anatomical and physiological studies designed to elucidate the mechanisms and neuronal systems involved in the physiological modulation of AS by mesencephalic sites, specifically the vlPAG and the dMRF. We suggest that these sites contain wake-promoting neurons that are likely inhibited by GABAergic systems; when these GABAergic systems are activated, AS occurs.
Acknowledgments
We are grateful to J. K. Engelhardt for his critical review of this manuscript. This work was supported by the following grants from the U.S. Public Health Service: NS23426, NS09999, and MH43362.
References (56)
- et al.
A neuroanatomical gradient in the pontine tegmentum for the cholinoceptive induction of desynchronized sleep signs
Brain Res
(1987) Functional characteristics of the midbrain periaqueductal gray
Prog Neurobiol
(1995)- et al.
Animal sleep: a review of sleep duration across phylogeny
Neurosci Biobehav Rev
(1984) - et al.
Control of motoneurones during sleep
- et al.
Cholinergic activation of medial pontine reticular formation neurons in vitro
Brain Res
(1989) - et al.
Narcolepsy: Diagnosis and management
Paradoxical sleep and its chemical/structural substrates in the brain
Neuroscience
(1991)Basic mechanisms of sleep-wake states
- et al.
GABA in locus coeruleus regulates spontaneous rapid eye movement sleep by acting on GABAA receptors in freely moving rats
Neurosci Lett
(1997) - et al.
Enhancement of acetylcholine release during paradoxical sleep in the dorsal tegmental field of the cat brain stem
Neurosci Lett
(1990)