Orexins increase cortical acetylcholine release and electroencephalographic activation through orexin-1 receptor in the rat basal forebrain during isoflurane anesthesia
Abstract
Cholinergic arousal system plays an important role in the maintenance of consciousness. The authors investigated whether the intrabasalis injection of orexin-A or orexin-B and the electrically stimulated pedunculopontine tegmentum nuclei (PPTg: the origin of cholinergic ascending pathways) may alter acetylcholine efflux and electroencephalographic activity in the somatosensory cortex in relation to the orexinergic system in isoflurane-anesthetized rats. Either orexin-A (10, 30, or 100 pmol) or orexin-B (10, 30, or 100 pmol) (n = 6 each) was injected into the basal forebrain while the electroencephalogram was measured during 1.0 minimum alveolar concentration (1.2%) isoflurane anesthesia. Injection of Ringer's solution was used as a control. The PPTg was electrically stimulated twice with the following conditions: 1-s stimulus train (0.2 ms, 100 Hz, 400 microA) per min for 20 min. Twenty minutes before the second PPTg stimulation, Ringer's solution or 20 microg SB334867, an orexin-1 receptor antagonist (n = 5 each) was injected into the basal forebrain. Injection of orexin-A (30 and 100 pmol) and orexin-B (100 pmol) significantly increased the acetylcholine efflux in the somatosensory cortex (P < 0.05). Injection of orexin-A (10...Continue Reading
References
Wake-promoting and sleep-suppressing actions of hypocretin (orexin): basal forebrain sites of action
The sedative component of anesthesia is mediated by GABA(A) receptors in an endogenous sleep pathway
Activity, modulation and role of basal forebrain cholinergic neurons innervating the cerebral cortex
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