Neurotransmission, chemical mechanism

Membrane Trafficking Membrane Fusion, Mechanisms of Neurotransmitter Production and Storage Neurotransmitter Uptake and Degradation Neurotransmission, Chemical Events in Synaptic Chemistry... 

Chemical neurotransmission is the way in which neurons communicate by releasing chemical substances that are received by the receptors in the next neuron (or the target) and excite or inhibit it. About 50% or more of dtug mechanisms are based on modification of chemical neurotransmission. 

The alterations in neurotransmitter activity which trigger or accompany the onset of natural sleep and distinguish slow wave or non-REM from REM sleep, provide one of the most compelling arguments in favour of chemical neurotransmission being specifically involved in mechanisms of conscious awareness. For an extensive review on neurochemistry and sleep, see Gottes-man (1999). 

There are a myriad of known and suspected mechanisms by which diseases can modify chemical neurotransmission. These can vary from no transmission, as in the case of a degenerated or absent neuron, to too much neurotransmission from a malfunction of the synapse. One of the key consequences of loss of neurons in neuro-degenerative disorders such as Parkinson s disease, Huntington s disease, amyotrophic lateral sclerosis (Lou Gehrig s disease), and Alzheimer s disease, is the fact that no neurotransmission occurs subsequent to neuronal loss (Fig. 4—24). This is a conceptually simple mechanism of disease action with profound consequences. It is also at least in part the mechanism of other disorders, such as stroke, multiple sclerosis, and virtually any disorder in which neurons are irreversibly damaged. 

Colchicine disrupts the movement of secretory vesicles within a cell, and thus interferes with chemical neurotransmission. If administered quickly or in elevatEd dose, the drug interferes with homeostatic mechanisms, particularly those mediated by the autonomic nervous system. Inhibition of medullary regulation of respiration, decreased thalamic control of core temperature, as well as inhibition of peripheral vasodilatation, leading to hypertension, may be seen. 

Nerve impulses elicit responses by hberating specific chemical neurotransmitters. Understanding the chemical mediation of nerve impulses provides the framework for our knowledge of the mechanism of action of drugs at these sites. The sequence of events involved in neurotransmission is of particular importance because pharmacologically active agents modulate the individual steps. 

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