ROLE OF THE LOCUS COERULEUS IN THE CONTROL OF PARADOXICAL SLEEP GENERATION IN THE CAT

摘要

Following the discovery of rapid eye movement (REM) sleep in humans by Aserinsky and Kleitman (1), a similar sleep state has been identified in the cat by Dement (6) and Jouvet and his colleagues (14), and called desynchronized or paradoxical sleep (PS). Using brain lesion and transection techniques, Jouvet showed, as early as 1962, that a state nearly identical to PS could be observed even after removal of all neural tissues above the level of the rostral pons and that the pons is the most critical region in the brain for PS generation (11). Jouvet further proposed that the activity of noradrenergic neurons in the nucleus locus coeruleus (LC; A6 cell group (5)) of the dorsolateral pontine tegmentum is critical for the generation of PS and its signs (12, 13). Subsequent studies revealed, however, that noradrenergic LC neurons cease firing just prior to and during PS (see ref. (9) for review), leading to the postulate that LC noradrenergic activity plays a critical inhibitory, instead of an executive, role in PS generation by inhibiting PS-executive or PS-on neurons located in the peri-LC region of the pons (8, 15, 16). The exact role of noradrenergic LC neurons in the tonic control of PS generation, however, still remains to be determined. In the present study, therefore, we have examined in vivo effects on behavioral states of microdialysis application to the LC of clonidine, a selective and potent agonist ofα_2 adrenoceptors, activation of which causes cessation of discharge of noradrenergic LC neurons.