Although cholinergic neurons represent a minute fraction of the neurons that make up the CNS, they regulate essentially every muscle, organ, gland, and neural region.32 The cholinergic systems in the CNS are diverse, diffuse, and thus certainly appealing as putative targets of volatile anesthetic action. The cholinergic basal forebrain contains cells that are thought to be involved with memory and arousal.32 Pontomes-encephalic cholinergic neurons appear to be involved with mechanisms of sleep, memory, and locomotor activity. n-nAChRs can serve either postsynaptic or presyn-aptic functions.32
The classical postsynaptic role of n-nAChRs is in the autonomic ganglia, where they are responsible for direct synaptic transmission. Cholinergic somatic and auto-nomic nerves control smooth and cardiac muscle as well as glandular secretion. Thus, inhibition of n-nAChRs may result in alterations of heart rate and blood pressure, common side effects of general anesthetics.
The n-nAChRs are thought to have an important presynaptic role in the CNS. There are many cells throughout the CNS that express n-nAChRs both on the soma and on their axonal terminals. Stimulation of these nAChRs results in the presynaptic augmentation of release of glutamate, GABA, dopamine, serotonin, norepinephrine, and ACh itself.28 This increase in release has been shown to augment synaptic transmission in many areas of the CNS, including medial habenula, diagonal band, laterodorsal tegmental nucleus, prefrontal cortex, primary visual cortex, and hippo-campus.32 The behavioral effects of general anesthetics are varied and include hypnosis, amnesia, analgesia, immobility, as well as hemodynamic, gastrointestinal, and thermoregulatory side effects. It is likely that multiple neurophysiologic mechanisms
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HYPNOTISM is by no means a new art. True, it has been developed into a science in comparatively recent years. But the principles of thought control have been used for thousands of years in India, ancient Egypt, among the Persians, Chinese and in many other ancient lands. Miracles of healing by the spoken word and laying on of hands are recorded in many early writings.