Biomaterial Database

Actions of general anaesthetics on synaptic transmission in the CNS. 1983

C D Richards

This article reviews the actions of general anaesthetics on synapses in the mammalian central nervous system. It is shown that during general anaesthesia, anaesthetics act primarily on the chemical transmission process itself and do not affect the conduction of impulses in nerve axons or change the electrical excitability of neurones. Virtually all general anaesthetics depress excitatory synaptic transmission at concentrations required for surgical anaesthesia but some, notably the barbiturates, also increase the intensity of inhibitory synaptic transmission. Detailed analysis has found that small concentrations of barbiturates increase the amount of inhibitory transmitter released but decrease the amount of excitatory transmitter released. In addition to these effects on the neurosecretory process, anaesthetics directly affect the sensitivity of the postsynaptic receptors to transmitter substances, although the effects vary between anaesthetics and receptors. It is concluded that general anaesthesia results from a summation of a number of effects which together tend to depress the excitability of the CNS as a whole.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D002490	Central Nervous System	The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges.	Cerebrospinal Axis,Axi, Cerebrospinal,Axis, Cerebrospinal,Central Nervous Systems,Cerebrospinal Axi,Nervous System, Central,Nervous Systems, Central,Systems, Central Nervous
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D000768	Anesthesia, General	Procedure in which patients are induced into an unconscious state through use of various medications so that they do not feel pain during surgery.	Anesthesias, General,General Anesthesia,General Anesthesias
D000777	Anesthetics	Agents capable of inducing a total or partial loss of sensation, especially tactile sensation and pain. They may act to induce general ANESTHESIA, in which an unconscious state is achieved, or may act locally to induce numbness or lack of sensation at a targeted site.	Anesthetic,Anesthetic Agents,Anesthetic Drugs,Anesthetic Effect,Anesthetic Effects,Agents, Anesthetic,Drugs, Anesthetic,Effect, Anesthetic,Effects, Anesthetic
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse
D013570	Synaptic Membranes	Cell membranes associated with synapses. Both presynaptic and postsynaptic membranes are included along with their integral or tightly associated specializations for the release or reception of transmitters.	Membrane, Synaptic,Membranes, Synaptic,Synaptic Membrane