Neurotransmitters fast-acting

Type / neurotransmitters These are the fast-acting neurotransmitters, which include glutamate, aspartate, 4-aminobutyrate and glycine. Around 90% of synapses in the brain use this class of neurotransmitter. 

The release of neuropeptides generally requires a more intense stimulus than that required for release of fastacting classical neurotransmitters. The more intense stimulus presumably results in more entry of Ca2+ into the presynaptic terminal, allowing Ca2+ to diffuse from its entry site to the LDCVs (Figs 18-3,18-4). As a result, the contribution of peptides vs. fast-acting conventional neurotransmitters to signaling can vary with the pattern of stimulation. For example, in Aplysia, several identified... 

Neurochemicals distinguish the reductionistic-type sensory pathways from the integrative-type action circuitry. Sensory pathways commonly use the excitatory neurotransmitters glutamate or aspartate at virtually every relay. Most actions along these pathways are mediated by the fast acting glutamate receptors ofthe iontropicvariety (i.e., AMPA and kainate receptors). Acetylcholine is... 

Fast-acting, class 1 (ionotropic) receptors. The neurotransmitter binds to the receptor protein and within milliseconds leads to a change in the permeability of the associated ion channel, allowing the influx of ions such as Ca ", Na", K", or Cl . 

FIGURE 2.2 The anatomy of the neuron. Communication between two neurons occurs at the synapse. The presynaptic neuron produces and releases the neurotransmitter into the synaptic cleft. Four mechanisms (1 ) are important to understand the function of most neurotransmitter systems. The release of neurotransmitter can be modulated via presynaptic receptors (1). The amount of neurotransmitter in the synaptic cleft can be decreased by reuptake into the presynaptic neuron (2) or via enzymatic degradation. Neurotransmitter effects at the target neuron are relayed via fast-acting ion channel—coupled receptors (3) or via slower-acting G protein—coupled receptors (4). Down-stream effects of postsynaptic receptors include the phosphorylation (P) of nuclear proteins. 

Figure 1.2 Fast-acting transmitters act by opening an ion channel (e.g. glutamate and GABA) while slower-acting neurotransmitters, often involved in tonic regulation, act through G-protein-coupled receptors (e.g. amines such as DA and 5-HT).

This is the major fast-acting excitatory neurotransmitter with a wide distribution in the brain. There are four main types of excitatory amino acid receptors N-methyl D-aspartate (NMDA), amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), kainate (these all regulate cation channels) and metabotropic (G-protein coupled). There are many subtypes within these groups. 

In addition to its structural role, phosphatidylinositol has a specialized function in membranes, acting as the source of inositol trisphosphate and diacylglycerol, which are produced as intracellular second messengers in response to fast-acting hormones and neurotransmitters (section 10.3.3). 

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