Neurobiologists once believed that the workings of the brain were guided exclusively by electrical signals; according to this theory, communication between neurons (brain cells) is possible because electrical impulses travel from one neuron to the next by literally leaping across the synapses (gaps between neurons). But many neurobiologists puzzled over how this impulse that runs through the cell; the electrical impulse is thereby transmitted to the receiving neuron.
This theory has gradually won acceptance in the scientific community, but for a long time little was known about the mechanism by which neurotransmitters manage to render the receiving neuron permeable to ions. In fact, some scientists remained skeptical of the theory because they had trouble imagining how the binding of a of receptors plays the pivotal role in mediating the conversion of chemical signals into electrical activity.
The new evidence shows that receptors for neurotransmitters contain both a neurotransmitter binding site and a separate region that functions as a channel for ions; attachment of the neurotransmitter to the binding site causes the receptor to change shape and so results in the opening of its channel component. Several types of receptors display enough similarities to constitute a family, known collectively as neurotransmitter-gated ion channels.
It has also been discovered that each of the receptors in this family comes in several varieties so that, for example, a GABA receptor in one part of the brain has slightly different properties than a GABA receptor in another part of the brain. This discovery is medically significant because it raises any number of debilitating conditions, including mood disorders, tissue damage associated with stroke, or Alzheimer’s disease.
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