Neurotransmitters eukaryotic cells

Chemical transmission between nerve cells involves multiple steps 167 Neurotransmitter release is a highly specialized form of the secretory process that occurs in virtually all eukaryotic cells 168 A variety of methods have been developed to study exocytosis 169 The neuromuscular junction is a well defined structure that mediates the presynaptic release and postsynaptic effects of acetylcholine 170 Quantal analysis defines the mechanism of release as exocytosis 172 Ca2+ is necessary for transmission at the neuromuscular junction and other synapses and plays a special role in exocytosis 174 Presynaptic events during synaptic transmission are rapid, dynamic and interconnected 175... 

Neurotransmitter release is a highly specialized form of the secretory process that occurs in virtually all eukaryotic cells. The fundamental similarity between the events in the nerve terminal that control neurotransmitter... 

Neurotransmission is based on the secretion of neurotransmitters from secretory vesicles in the presynaptic membrane and the binding of the agonists by receptors on the postsynaptic membrane. The transmitters have to travel only about 20 nm across the synaptic cleft, whereas neurohormones may act on much more distant receptors. The biogenesis of the secretory vesicles and the receptors are intimately connected with the secretory pathway of the eukaryotic cells. In this system a series of membrane-bound structures mediate the transfer of exported proteins from their site of synthesis at the rough endoplasmic reticulum to their site of discharge at the plasma membrane. We will use the chromaffin granules (storage vesicles of the adrenal medulla) as an example for secretory vesicles, and the acetylcholine receptor for receptors of neurotransmitters. 

Ion channels are essential for a wide range of functions such as neurotransmitters secretion and muscle contraction. Ion channels mediate Na, Ca +, and Cl conductance induced by membrane potential changes. These channels propagate action potentials in excitable cells and are also involved in the regulation of membrane potential and intracellular Ca + transients in most eukaryotic cells. About 300 genes code for subunits of voltage-gated ion channels. 

We begin this chapter with two sections that describe general principles and techniques that are relevant to most signaling systems. In the remainder of the chapter, we concentrate on the huge class of cell-surface receptors that activate trimeric G proteins. Receptors of this type, commonly called G protein-coupled receptors (GPCRs), are found In all eukaryotic cells from yeast to man. The human genome, for Instance, encodes several thousand G protein-coupled receptors. These Include receptors In the visual, olfactory (smell), and gustatory (taste) systems, many neurotransmitter receptors, and most of the receptors for hormones that control carbohydrate, amino acid, and fat metabolism. 

The process by which eukaryotic cells release packets of molecules v(e.g., neurotransmitters) to the environment by fusing vesicles formed in the cytoplasm with the plasma membrane. 

As indicated in section 1.3, cytosolic Ca oscillations, which occur in a variety of cell types as a result of stimulation by hormones or neurotransmitters, are among the most widespread of cellular rhythms, besides oscillations driven by periodic variations of the membrane potential in electrically excitable cells. These oscOlations, whose period varies from seconds to minutes depending on the cell type, sometimes occur spontaneously. Part V is devoted to this phenomenon, which clearly represents the most significant addition to the field of biochemical oscillations over the last decade, in addition to the evidence that has acciunulated to show that a continuous biochemical oscillator controls the eukaryotic cell cycle (see below). Experimental work on Ca oscillations has increased so much over the last years that it is by now the most studied biochemical rhythm. 

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