tration triggers the release of neurotransmitter moleculesinto the syn - PDF document

108A& RESEARCH tration triggers the release of neurotransmitter moleculesinto the synaptic cleft.Two large groups of receptors exist that elicit specificresponses in the receptor cell: Receptors that act as ligand- Ligand-Gated Channel Receptors. When a neurotransmit-ter molecule binds to a receptor that acts as a ligand-gatedcharged ions. An increase of negative charge within the cell Second Messenger-Linked Receptors . Second messengers(e.g., G proteins) are molecules that help relay signals fromto second messenger-linked receptors, such as dopamine,feedback process that can affect future communicationof the signals the neuron receives will have excitatory ef- EUROTRANSMITTERSAND Among the neurotransmitters of most interest to alcoholresearchers are dopamine, serotonin, glutamate, gamma-Neurons that release these substances form the basis ofcomplex network of pathways and feedback loops. Theintegrated activity of these circuits regulates mood, activi-  ALCOHOL AND DOPAMINE Gaetano Di Chiara, M.D. release by the target neurons. Dopamine-containingter repeated alcohol administration, which may con- EYWORDS:dopamine; dopaminergic receptors; cell sig- M(i.e., neurotransmitters) are affected by alcohol.attention, because several studies have found that alcoholcalled the nucleus accumbens (NAc) (Di Chiara andand dependence, also with the intent of finding new phar-role in alcohol reinforcement. NEUROTRANSMITTER REVIEW THE PRINCIPLES OF NERVE CELLCOMMUNICATION Tactivity of the nervous system. It conveys informa-neuron itself, information is passed along through thetioning; and (3) the axon, a long, thin fiber that carriesbody. For example, if you step barefooted on a sharp object, S The mechanism underlying signal transmission withinneurons is based on voltage differences (i.e., potentials)2+). Ions enter and exit thecell through specific protein channels in the cellbrane. The channels neurotransmitters or to changes in the cellpotential. The resulting redistribution of electric charge Communication among neurons typically occurs acrossmicroscopic gaps called synaptic clefts. Each neuron maymust be converted into a chemical one. This conversion2+to enter the cell. The increase in intracellular Ca2+concen- VO. 2, 1997107 NEUROTRANSMITTER REVIEW Signal transmission across the synaptic cleft. The bindingof neurotransmitters (shown as triangles) to receptors thatthat can produce changes in cell function. In this schematic,the first component of such a signaling cascade is a G protein.nerve cellPresynapticnerve cellReceptor Ligand-gatedion channel ReceptorbindingCellrelease