Reticular system

It is important to emphasise that a lesion of the reticular system disrupts a number of afferent inputs to the cortex. Particularly important in this respect are the mono-aminergic (especially noradrenaline, 5-HT and histamine) and cholinergic pathways. When the ascending inputs from these neurons are destroyed, sleep is passive and not at all like natural sleep which, as detailed above, has distinct phases and depends on brainstem influences on cortical function. How these different neurotransmitters might influence sleep and arousal will be considered next. 

The posterior, lateral and medial hypothalamus is a continuation of, and is closely related to, the ascending activating reticular system (Passouant, 1967). Clinical evidence in man shows that lesions of the posterior hypothalamus produce sleepiness. Moreover, depending on the exact site as well as the extent of the lesion, hypersomnia, coma or changes in the circadian rhythmicity of sleep results (Parkes, 1985). Conversely, lesions of the anterior hypothalamus results in insomnia (von Economo, 1930). 

Shute CCD, Lewis PR The ascending cholinergic reticular system neocortical, olfactory and subcortical projections. Brain 90 521-540, 1967... 

Activation-synthesis model. (A) Systems model. (B) Wiring diagram. As a result of disinhibition caused by cessation of aminergic neuronal firing, brainstem reticular systems autoactivate. Their outputs have effects including depolarization of afferent terminals causing phasic presynaptic inhibition and blockade of external stimuli, especially during the bursts of REM, and postsynaptic hyperpolarization... 

Two other systems of importance in the brain are the reticular system and the limbic system. The... 

Benzodiazepines exert central depressant effects on spinal reflexes, in part mediated by the brainstem reticular system.3 For example, chlordiazepoxide depresses the duration of electrical after-discharge in the limbic system. Most benzodiazepines elevate the seizure threshold and therefore may be used as anticonvulsant medications. Diazepam, clonazepam, and clorazepate may be prescribed for this therapeutic purpose. 

The effect of etomidate on catatonia, similar to that of amobarbital, was thought to be due to enhanced GABA receptor function in patients with an overactive reticular system. 

Mechanism of Action. These drugs exert a direct effect on susceptible protozoa by causing degeneration of subcellular components such as the nucleus and reticular system within the parasite. 

Moruzzi G. The physiologic properties of the brain-stem reticular system. In Adrian ED, Bremmer F, Jasper HH, eds. Brain Mechanisms and Consciousness. Oxford Blackwell, 1954 21 18. 

In contrast, the hydrocarbon contact sex pheromone of the German cockroach is synthesized in Class II oenocytes associated with the abdominal stemites (Young et al., 1999 Fan et al., 2002). These large oenocytes, ranging up to 50 p in in diameter in B. germanica, have abundant mitochondria and extensive smooth endoplasmic reticulum (Fan et al., 2002). Although the oenocytes are associated with abdominal stemites, the hydrocarbons are released into the hemolymph and loaded, probably across a plasma membrane reticular system, into high-density lipophorin. The lipophorin then likely transports the hydrocarbon to epidermal cells for release onto the cuticle (Fan et al., 2002). 

Jackson, A., and Locke, M. (1989). The formation of plasma membrane reticular systems in the oenocytes of an insect. Tissue Cell, 21,463 473. 

Using the techniques of electrical stimulation and surgical alterations of the brain that led to Moruzzi and Magoun s concept of activation of a reticular system in the brain, the French neurophysiologist Michel Jouvet, working in Lyons from the mid-1950s onward, established once and for all that brain activation did occur and that it occurred spontaneously in sleep. 

Effects on GABA/ receptors in reticular systems (particularly substantia nigra) Triple therapy in soman research... 

Consciousness is defined as the totality of mental and emotional processes perceived as current events in combination with an awareness of the subjectivity of experience. Quantitatively impaired consciousness is the collective term for disturbances in awareness (= restricted vigilance). This condition is characterized by a limited readiness to show interest and concern, restricted attentiveness and impaired elements of consciousness. The activity of the ascending reticular system of the reticular formation is compromised, a condition which is generally accompanied by changes in the electroencephalogram (EEG). Moreover, disorders or loss of function are displayed in the area of the cerebral hemispheres and/or their afferent pathways, which are responsible for the subjective sensation of consciousness. Differentiation is made between four types of clouded consciousness (W. Hacke, 1986) ... 

The nucleus basalis of Meynert, located in the basal forebrain, is the main location of the cholinergic neurons. The cholinergic neurons project to the amygdala, hippocampus and other parts of the neocortex. Additional cholinergic neurons in the reticular system also project to the cerebral cortex, the limbic system, the hypothalamus, and the thalamus. Acetylcholine is... 

It should be clear that in comparison to the present knowledge on Na -K+ ATPase, the current understanding of Ca transport is sparse. The relative importance of plasmalemmal, mitochondrial, and reticular systems in the overall regulation and control of free cytoplasmic Ca remains to be elucidated and is obviously a fruitful area of research for the future. 

Fonnum The evidence that cholinergic terminals and not cell bodies are present in the caudate nucleus is based on the electron microscopy of AChE by Lewis and Shute (1967) in that region. Acetylcholinesterase seems to be bound within the terminals and not on the cells, that is within the cell reticular system. Further evidence is given by the experiment of Lewis and Shute which shows that if you cut the pathway between the substantia nigra and the caudate nucleus, the AChE activity seems to disappear. 

Lewis, P. R. and Shute, C. C. D. (1967) The cholinergic limbic system projections to hippocampal formation, medial cortex, nuclei of the ascending cholinergic reticular system and the subfornical organ and supra-optic crest. Brain, 90,521-540. 

Promethazine causes sedation by reducing stimuli to the brain stem reticular system. Like other antihistamines, promethazine has significant anticholinergic effects it should be used with caution in patients with narrow-angle glaucoma, peptic ulcer, or pyloroduodenal obstruction or urinary bladder obstruction from prostatic hypertrophy or narrowing of the bladder neck. It also should be used with caution in patients with CVD or hypertension because of the risk of palpitations with acute or chronic respiratory dysfunction (especially children) because promazine may depress the cough reflex. 

The multiplicity of synapses in the mid-brain and hypothalamus makes the reticular system particularly susceptible to chemical influences and a large number of drugs are capable of modifying its activity, thus producing changes in the level of consciousness, alertness and behavioural responsiveness. 

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