And REM sleep

Although histamine has mixed excitatory and inhibitory effects on central neurons, those antihistamines (Hi-receptor antagonists) that enter the brain produce sedation this indicates that the predominant overall effect of histamine is excitatory. The preferred explanation for this rests on evidence that histaminergic neurons in the posterior hypothalamus are active in waking and silent in deep SWS and REM sleep. 

A link between 5-HT release and increased waking is supported by evidence from in vivo microdialysis of cats and rats. This has confirmed that the extracellular concentration of 5-HT in all brain regions studied to date is lower during both SWS and REM sleep than in the awake state (see Portas, Bjorvatn and Ursin 2000). Interestingly, if behaviour is maintained at a constant level, the activity of 5-HT neurons does not show circadian variation although 5-HT turnover in the brain areas to which they project... 

Figure 22.9 Summary of the influence of varying factors on sleep and waking. The EEG is shown diagramatically in the typical arousal (awake) state and in both non-REM (slow wave) and REM sleep. Appropriate activity levels, high or low, are shown for the different factors such as light input, melatonin secretion or ACh, NA, and 5-HT function in the different phases...

Neuroanatomical and neurochemical basis of wakefulness and REM sleep systems... 

Overview of brain regions controlling wakefulness and REM sleep... 

Figure 2.1 Schematic of the rat brain (sagittal section) showing the approximate location of important brain structures controlling wakefulness and REM sleep. Abbreviations AH, anterior hypothalamus BF, basal forebrain DL pons, dorsolateral pons (rapid eye movement sleep control area) M-RA, Magoun/Rhines inhibitory area in the ventral medulla PH, posterior hypothalamus.

The concept of chemical neurotransmission originated in the 1920s with the classic experiments of Otto Loewi (which were themselves inspired by a dream), who demonstrated that by transferring the ventricular fluid of a stimulated frog heart onto an unstimulated frog heart he could reproduce the effects of a (parasympathetic) nerve stimulus on the unstimulated heart (Loewi Navratil, 1926). Subsequently, it was found that acetylcholine was the neurotransmitter released from these parasympathetic nerve fibers. As well as playing a critical role in synaptic transmission in the autonomic nervous system and at vertebrate neuromuscular junctions (Dale, 1935), acetylcholine plays a central role in the control of wakefulness and REM sleep. Some have even gone as far as to call acetylcholine a neurotransmitter correlate of consciousness (Perry et al., 1999). 

The development of antibodies against ChAT allowed the distribution of neurons producing acetylcholine in the nervous system to be revealed (Mesulam et al., 1983 Armstrong et al., 1983 Jones Beaudet, 1987 Vincent Reiner, 1987). In the context of control of wakefulness and REM sleep two groups of cholinergic neurons are of primary importance. Neurons located in the basal forebrain and medial septum provide the cholinergic innervation of the cerebral... 

Solms, M. (2000). Dreaming and REM sleep are controlled by different brain mechanisms. Behav. Brain Sci. 23, 843-50 discussion 904-1121. 

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