Tetrodotoxin
An aminoperhydroquinazoline poison found mainly in the liver and ovaries of fishes in the order TETRAODONTIFORMES, which are eaten. The toxin causes paresthesia and paralysis through interference with neuromuscular conduction.
Saxitoxin
A compound that contains a reduced purine ring system but is not biosynthetically related to the purine alkaloids. It is a poison found in certain edible mollusks at certain times; elaborated by GONYAULAX and consumed by mollusks, fishes, etc. without ill effects. It is neurotoxic and causes RESPIRATORY PARALYSIS and other effects in MAMMALS, known as paralytic SHELLFISH poisoning.
Sodium Channel Blockers
A class of drugs that act by inhibition of sodium influx through cell membranes. Blockade of sodium channels slows the rate and amplitude of initial rapid depolarization, reduces cell excitability, and reduces conduction velocity.
Sodium Channels
Ion channels that specifically allow the passage of SODIUM ions. A variety of specific sodium channel subtypes are involved in serving specialized functions such as neuronal signaling, CARDIAC MUSCLE contraction, and KIDNEY function.
Veratridine
A benzoate-cevane found in VERATRUM and Schoenocaulon. It activates SODIUM CHANNELS to stay open longer than normal.
Action Potentials
Sodium
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).
Atropine
An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.
Tetraodontiformes
Muscle Contraction
A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.
Guinea Pigs
Muscle, Smooth
Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)
Fishes, Poisonous
Protoveratrines
Veratrine
Veratrine is a mixture of alkaloids, primarily veratridine and cevadine, obtained from the seeds of various plants of the genus Schoenocaulon (formerly Veratrum), known to stimulate sodium channels in nerve membranes, leading to depolarization and prolonged action potentials.
Potassium
An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
Electrophysiology
Neurons
Guanethidine
An antihypertensive agent that acts by inhibiting selectively transmission in post-ganglionic adrenergic nerves. It is believed to act mainly by preventing the release of norepinephrine at nerve endings and causes depletion of norepinephrine in peripheral sympathetic nerve terminals as well as in tissues.
Calcium
A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.
Ion Channels
Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.
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.
Tetraethylammonium Compounds
Tetraethylammonium compounds refer to a group of organic salts containing the tetraethylammonium ion (N(C2H5)4+), which is characterized by four ethyl groups bonded to a central nitrogen atom, and are commonly used in research and medicine as pharmacological tools for studying ion channels.
Hexamethonium Compounds
Hexamethonium
A nicotinic cholinergic antagonist often referred to as the prototypical ganglionic blocker. It is poorly absorbed from the gastrointestinal tract and does not cross the blood-brain barrier. It has been used for a variety of therapeutic purposes including hypertension but, like the other ganglionic blockers, it has been replaced by more specific drugs for most purposes, although it is widely used a research tool.
Anesthetics, Local
Drugs that block nerve conduction when applied locally to nerve tissue in appropriate concentrations. They act on any part of the nervous system and on every type of nerve fiber. In contact with a nerve trunk, these anesthetics can cause both sensory and motor paralysis in the innervated area. Their action is completely reversible. (From Gilman AG, et. al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed) Nearly all local anesthetics act by reducing the tendency of voltage-dependent sodium channels to activate.
Poisons
Ileum
Toxins, Biological
Patch-Clamp Techniques
An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.
Acetylcholine
Procaine
Neurilemma
The outermost cytoplasmic layer of the SCHWANN CELLS covering NERVE FIBERS.
Rats, Sprague-Dawley
Batrachotoxins
Batrachotoxin is the 20-alpha-bromobenzoate of batrachotoxin A; they are toxins from the venom of a small Colombian frog, Phyllobates aurotaenia, cause release of acetylcholine, destruction of synaptic vesicles and depolarization of nerve and muscle fibers.
Lidocaine
A local anesthetic and cardiac depressant used as an antiarrhythmia agent. Its actions are more intense and its effects more prolonged than those of PROCAINE but its duration of action is shorter than that of BUPIVACAINE or PRILOCAINE.
Anura
Rana esculenta
Marine Toxins
Toxic or poisonous substances elaborated by marine flora or fauna. They include also specific, characterized poisons or toxins for which there is no more specific heading, like those from poisonous FISHES.
Decapodiformes
Calcium Channel Blockers
A class of drugs that act by selective inhibition of calcium influx through cellular membranes.
Neurotransmitter Agents
Substances used for their pharmacological actions on any aspect of neurotransmitter systems. Neurotransmitter agents include agonists, antagonists, degradation inhibitors, uptake inhibitors, depleters, precursors, and modulators of receptor function.
Aconitine
A C19 norditerpenoid alkaloid (DITERPENES) from the root of ACONITUM plants. It activates VOLTAGE-GATED SODIUM CHANNELS. It has been used to induce ARRHYTHMIAS in experimental animals and it has antiinflammatory and antineuralgic properties.
Norepinephrine
Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.
Dose-Response Relationship, Drug
Colon
Myenteric Plexus
One of two ganglionated neural networks which together form the ENTERIC NERVOUS SYSTEM. The myenteric (Auerbach's) plexus is located between the longitudinal and circular muscle layers of the gut. Its neurons project to the circular muscle, to other myenteric ganglia, to submucosal ganglia, or directly to the epithelium, and play an important role in regulating and patterning gut motility. (From FASEB J 1989;3:127-38)
Cnidarian Venoms
Neurotoxins
Serotonin
A biochemical messenger and regulator, synthesized from the essential amino acid L-TRYPTOPHAN. In humans it is found primarily in the central nervous system, gastrointestinal tract, and blood platelets. Serotonin mediates several important physiological functions including neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity. Multiple receptor families (RECEPTORS, SEROTONIN) explain the broad physiological actions and distribution of this biochemical mediator.
Conotoxins
Peptide neurotoxins from the marine fish-hunting snails of the genus CONUS. They contain 13 to 29 amino acids which are strongly basic and are highly cross-linked by disulfide bonds. There are three types of conotoxins, omega-, alpha-, and mu-. OMEGA-CONOTOXINS inhibit voltage-activated entry of calcium into the presynaptic membrane and therefore the release of ACETYLCHOLINE. Alpha-conotoxins inhibit the postsynaptic acetylcholine receptor. Mu-conotoxins prevent the generation of muscle action potentials. (From Concise Encyclopedia Biochemistry and Molecular Biology, 3rd ed)
Rats, Wistar
Scorpion Venoms
Venoms from animals of the order Scorpionida of the class Arachnida. They contain neuro- and hemotoxins, enzymes, and various other factors that may release acetylcholine and catecholamines from nerve endings. Of the several protein toxins that have been characterized, most are immunogenic.
Cesium
A member of the alkali metals. It has an atomic symbol Cs, atomic number 50, and atomic weight 132.91. Cesium has many industrial applications, including the construction of atomic clocks based on its atomic vibrational frequency.
Methysergide
An ergot derivative that is a congener of LYSERGIC ACID DIETHYLAMIDE. It antagonizes the effects of serotonin in blood vessels and gastrointestinal smooth muscle, but has few of the properties of other ergot alkaloids. Methysergide is used prophylactically in migraine and other vascular headaches and to antagonize serotonin in the carcinoid syndrome.
NAV1.8 Voltage-Gated Sodium Channel
6-Cyano-7-nitroquinoxaline-2,3-dione
GABA Antagonists
Drugs that bind to but do not activate GABA RECEPTORS, thereby blocking the actions of endogenous GAMMA-AMINOBUTYRIC ACID and GABA RECEPTOR AGONISTS.
Ranvier's Nodes
Regularly spaced gaps in the myelin sheaths of peripheral axons. Ranvier's nodes allow saltatory conduction, that is, jumping of impulses from node to node, which is faster and more energetically favorable than continuous conduction.
Neuromuscular Depolarizing Agents
Drugs that interrupt transmission at the skeletal neuromuscular junction by causing sustained depolarization of the motor end plate. These agents are primarily used as adjuvants in surgical anesthesia to cause skeletal muscle relaxation.
Vasoactive Intestinal Peptide
A highly basic, 28 amino acid neuropeptide released from intestinal mucosa. It has a wide range of biological actions affecting the cardiovascular, gastrointestinal, and respiratory systems and is neuroprotective. It binds special receptors (RECEPTORS, VASOACTIVE INTESTINAL PEPTIDE).
Enteric Nervous System
Two ganglionated neural plexuses in the gut wall which form one of the three major divisions of the autonomic nervous system. The enteric nervous system innervates the gastrointestinal tract, the pancreas, and the gallbladder. It contains sensory neurons, interneurons, and motor neurons. Thus the circuitry can autonomously sense the tension and the chemical environment in the gut and regulate blood vessel tone, motility, secretions, and fluid transport. The system is itself governed by the central nervous system and receives both parasympathetic and sympathetic innervation. (From Kandel, Schwartz, and Jessel, Principles of Neural Science, 3d ed, p766)
Excitatory Amino Acid Antagonists
Tubocurarine
A neuromuscular blocker and active ingredient in CURARE; plant based alkaloid of Menispermaceae.
Nerve Endings
Branch-like terminations of NERVE FIBERS, sensory or motor NEURONS. Endings of sensory neurons are the beginnings of afferent pathway to the CENTRAL NERVOUS SYSTEM. Endings of motor neurons are the terminals of axons at the muscle cells. Nerve endings which release neurotransmitters are called PRESYNAPTIC TERMINALS.
Phentolamine
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.
Voltage-Gated Sodium Channels
Apamin
4-Aminopyridine
Evoked Potentials
Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported.
Microelectrodes
Substance P
Electrophorus
A genus of fish, in the family GYMNOTIFORMES, capable of producing an electric shock that immobilizes fish and other prey. The species Electrophorus electricus is also known as the electric eel, though it is not a true eel.
NAV1.2 Voltage-Gated Sodium Channel
A voltage-gated sodium channel subtype that mediates the sodium ion permeability of excitable membranes. Defects in the SCN2A gene which codes for the alpha subunit of this sodium channel are associated with benign familial infantile seizures type 3, and early infantile epileptic encephalopathy type 11.
Neural Conduction
Physostigmine
Bicuculline
Crustacea
A large subphylum of mostly marine ARTHROPODS containing over 42,000 species. They include familiar arthropods such as lobsters (NEPHROPIDAE), crabs (BRACHYURA), shrimp (PENAEIDAE), and barnacles (THORACICA).
Pleurobranchaea
Nifedipine
A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.
Carbachol
Synaptosomes
Pinched-off nerve endings and their contents of vesicles and cytoplasm together with the attached subsynaptic area of the membrane of the post-synaptic cell. They are largely artificial structures produced by fractionation after selective centrifugation of nervous tissue homogenates.
Bethanechol
A slowly hydrolyzing muscarinic agonist with no nicotinic effects. Bethanechol is generally used to increase smooth muscle tone, as in the GI tract following abdominal surgery or in urinary retention in the absence of obstruction. It may cause hypotension, HEART RATE changes, and BRONCHIAL SPASM.
Barium
Parasympathetic Nervous System
The craniosacral division of the autonomic nervous system. The cell bodies of the parasympathetic preganglionic fibers are in brain stem nuclei and in the sacral spinal cord. They synapse in cranial autonomic ganglia or in terminal ganglia near target organs. The parasympathetic nervous system generally acts to conserve resources and restore homeostasis, often with effects reciprocal to the sympathetic nervous system.
Serotonin Antagonists
Germine Acetates
Neural Inhibition
The function of opposing or restraining the excitation of neurons or their target excitable cells.
Dimethylphenylpiperazinium Iodide
A selective nicotinic cholinergic agonist used as a research tool. DMPP activates nicotinic receptors in autonomic ganglia but has little effect at the neuromuscular junction.
Excitatory Postsynaptic Potentials
Depolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during neurotransmission. Excitatory postsynaptic potentials can singly or in summation reach the trigger threshold for ACTION POTENTIALS.
omega-Conotoxin GVIA
A neurotoxic peptide, which is a cleavage product (VIa) of the omega-Conotoxin precursor protein contained in venom from the marine snail, CONUS geographus. It is an antagonist of CALCIUM CHANNELS, N-TYPE.
Ouabain
Hippocampus
A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.
Mollusca
A phylum of the kingdom Metazoa. Mollusca have soft, unsegmented bodies with an anterior head, a dorsal visceral mass, and a ventral foot. Most are encased in a protective calcareous shell. It includes the classes GASTROPODA; BIVALVIA; CEPHALOPODA; Aplacophora; Scaphopoda; Polyplacophora; and Monoplacophora.
Potassium Chloride
Nitroarginine
An inhibitor of nitric oxide synthetase which has been shown to prevent glutamate toxicity. Nitroarginine has been experimentally tested for its ability to prevent ammonia toxicity and ammonia-induced alterations in brain energy and ammonia metabolites. (Neurochem Res 1995:200(4):451-6)
Verapamil
A calcium channel blocker that is a class IV anti-arrhythmia agent.
Tachyphylaxis
Vagus Nerve
The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx).
2-Amino-5-phosphonovalerate
The D-enantiomer is a potent and specific antagonist of NMDA glutamate receptors (RECEPTORS, N-METHYL-D-ASPARTATE). The L form is inactive at NMDA receptors but may affect the AP4 (2-amino-4-phosphonobutyrate; APB) excitatory amino acid receptors.
Cadmium
An element with atomic symbol Cd, atomic number 48, and atomic weight 114. It is a metal and ingestion will lead to CADMIUM POISONING.
Glutamic Acid
A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.
Purkinje Fibers
Cobalt
Quinoxalines
Rats, Inbred Strains
Sodium Channel Agonists
A class of drugs that stimulate sodium influx through cell membrane channels.
Glycine Agents
Tachykinins
A family of biologically active peptides sharing a common conserved C-terminal sequence, -Phe-X-Gly-Leu-Met-NH2, where X is either an aromatic or a branched aliphatic amino acid. Members of this family have been found in mammals, amphibians, and mollusks. Tachykinins have diverse pharmacological actions in the central nervous system and the cardiovascular, genitourinary, respiratory, and gastrointestinal systems, as well as in glandular tissues. This diversity of activity is due to the existence of three or more subtypes of tachykinin receptors.
Scopolamine Hydrobromide
An alkaloid from SOLANACEAE, especially DATURA and SCOPOLIA. Scopolamine and its quaternary derivatives act as antimuscarinics like ATROPINE, but may have more central nervous system effects. Among the many uses are as an anesthetic premedication, in URINARY INCONTINENCE, in MOTION SICKNESS, as an antispasmodic, and as a mydriatic and cycloplegic.
Cells, Cultured
Cholinergic Fibers
Nerve fibers liberating acetylcholine at the synapse after an impulse.
Cats
The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)
Strychnine
Ciguatoxins
Calcium Channels
Voltage-dependent cell membrane glycoproteins selectively permeable to calcium ions. They are categorized as L-, T-, N-, P-, Q-, and R-types based on the activation and inactivation kinetics, ion specificity, and sensitivity to drugs and toxins. The L- and T-types are present throughout the cardiovascular and central nervous systems and the N-, P-, Q-, & R-types are located in neuronal tissue.
Mollusk Venoms
Venoms from mollusks, including CONUS and OCTOPUS species. The venoms contain proteins, enzymes, choline derivatives, slow-reacting substances, and several characterized polypeptide toxins that affect the nervous system. Mollusk venoms include cephalotoxin, venerupin, maculotoxin, surugatoxin, conotoxins, and murexine.
Aminopyridines
Oxocins
Sciatic Nerve
A nerve which originates in the lumbar and sacral spinal cord (L4 to S3) and supplies motor and sensory innervation to the lower extremity. The sciatic nerve, which is the main continuation of the sacral plexus, is the largest nerve in the body. It has two major branches, the TIBIAL NERVE and the PERONEAL NERVE.
Autonomic Fibers, Postganglionic
Nerve fibers which project from cell bodies of AUTONOMIC GANGLIA to SYNAPSES on target organs.
Reserpine
An alkaloid found in the roots of Rauwolfia serpentina and R. vomitoria. Reserpine inhibits the uptake of norepinephrine into storage vesicles resulting in depletion of catecholamines and serotonin from central and peripheral axon terminals. It has been used as an antihypertensive and an antipsychotic as well as a research tool, but its adverse effects limit its clinical use.
Potassium Channels
Cell membrane glycoproteins that are selectively permeable to potassium ions. At least eight major groups of K channels exist and they are made up of dozens of different subunits.
N-Methylaspartate
Neurokinin A
A mammalian neuropeptide of 10 amino acids that belongs to the tachykinin family. It is similar in structure and action to SUBSTANCE P and NEUROKININ B with the ability to excite neurons, dilate blood vessels, and contract smooth muscles, such as those in the BRONCHI.
Muscarinic Antagonists
Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system.
Astacoidea
A superfamily of various freshwater CRUSTACEA, in the infraorder Astacidea, comprising the crayfish. Common genera include Astacus and Procambarus. Crayfish resemble lobsters, but are usually much smaller.
Nephropidae
Family of large marine CRUSTACEA, in the order DECAPODA. These are called clawed lobsters because they bear pincers on the first three pairs of legs. The American lobster and Cape lobster in the genus Homarus are commonly used for food.
Receptors, Neurokinin-2
A class of cell surface receptors for tachykinins that prefers neurokinin A; (NKA, substance K, neurokinin alpha, neuromedin L), neuropeptide K; (NPK); or neuropeptide gamma over other tachykinins. Neurokinin-2 (NK-2) receptors have been cloned and are similar to other G-protein coupled receptors.
Urinary Bladder
Drug Interactions
Curare
Rabbits
Lithium
An element in the alkali metals family. It has the atomic symbol Li, atomic number 3, and atomic weight [6.938; 6.997]. Salts of lithium are used in treating BIPOLAR DISORDER.
Presynaptic Terminals
The distal terminations of axons which are specialized for the release of neurotransmitters. Also included are varicosities along the course of axons which have similar specializations and also release transmitters. Presynaptic terminals in both the central and peripheral nervous systems are included.
Neuroeffector Junction
Gallopamil
Coronary vasodilator that is an analog of iproveratril (VERAPAMIL) with one more methoxy group on the benzene ring.
Baclofen
A GAMMA-AMINOBUTYRIC ACID derivative that is a specific agonist of GABA-B RECEPTORS. It is used in the treatment of MUSCLE SPASTICITY, especially that due to SPINAL CORD INJURIES. Its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission.
Dogs
Spinal Cord
Autonomic Agents
Picrotoxin
A noncompetitive antagonist at GABA-A receptors and thus a convulsant. Picrotoxin blocks the GAMMA-AMINOBUTYRIC ACID-activated chloride ionophore. Although it is most often used as a research tool, it has been used as a CNS stimulant and an antidote in poisoning by CNS depressants, especially the barbiturates.
Ion Channel Gating
The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability.
Propranolol
A widely used non-cardioselective beta-adrenergic antagonist. Propranolol has been used for MYOCARDIAL INFARCTION; ARRHYTHMIA; ANGINA PECTORIS; HYPERTENSION; HYPERTHYROIDISM; MIGRAINE; PHEOCHROMOCYTOMA; and ANXIETY but adverse effects instigate replacement by newer drugs.
Receptors, Serotonin
Receptors, Tachykinin
Cell surface proteins that bind TACHYKININS with high affinity and trigger intracellular changes influencing the behavior of cells. Three classes of tachykinin receptors have been characterized, the NK-1; NK-2; and NK-3; which prefer, respectively, SUBSTANCE P; NEUROKININ A; and NEUROKININ B.
Peristalsis
A movement, caused by sequential muscle contraction, that pushes the contents of the intestines or other tubular organs in one direction.
Spider Venoms
Venoms of arthropods of the order Araneida of the ARACHNIDA. The venoms usually contain several protein fractions, including ENZYMES, hemolytic, neurolytic, and other TOXINS, BIOLOGICAL.
Pempidine
Organ Culture Techniques
Olfactory Nerve
The 1st cranial nerve. The olfactory nerve conveys the sense of smell. It is formed by the axons of OLFACTORY RECEPTOR NEURONS which project from the olfactory epithelium (in the nasal epithelium) to the OLFACTORY BULB.
Magnesium
NAV1.7 Voltage-Gated Sodium Channel
Scorpions
Arthropods of the order Scorpiones, of which 1500 to 2000 species have been described. The most common live in tropical or subtropical areas. They are nocturnal and feed principally on insects and other arthropods. They are large arachnids but do not attack man spontaneously. They have a venomous sting. Their medical significance varies considerably and is dependent on their habits and venom potency rather than on their size. At most, the sting is equivalent to that of a hornet but certain species possess a highly toxic venom potentially fatal to humans. (From Dorland, 27th ed; Smith, Insects and Other Arthropods of Medical Importance, 1973, p417; Barnes, Invertebrate Zoology, 5th ed, p503)
Receptors, Cholinergic
Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology.
Parasympatholytics
Agents that inhibit the actions of the parasympathetic nervous system. The major group of drugs used therapeutically for this purpose is the MUSCARINIC ANTAGONISTS.
Cell Membrane Permeability
Aminobutyrates
Ganglia, Spinal
Sensory ganglia located on the dorsal spinal roots within the vertebral column. The spinal ganglion cells are pseudounipolar. The single primary branch bifurcates sending a peripheral process to carry sensory information from the periphery and a central branch which relays that information to the spinal cord or brain.
Nerve Fibers
Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.
GABA-A Receptor Antagonists
Riluzole
Dibucaine
Histamine
Rana pipiens
Submucous Plexus
One of two ganglionated neural networks which together form the enteric nervous system. The submucous (Meissner's) plexus is in the connective tissue of the submucosa. Its neurons innervate the epithelium, blood vessels, endocrine cells, other submucosal ganglia, and myenteric ganglia, and play an important role in regulating ion and water transport. (From FASEB J 1989;3:127-38)
Motor Endplate
The specialized postsynaptic region of a muscle cell. The motor endplate is immediately across the synaptic cleft from the presynaptic axon terminal. Among its anatomical specializations are junctional folds which harbor a high density of cholinergic receptors.
Sympatholytics
Drugs that inhibit the actions of the sympathetic nervous system by any mechanism. The most common of these are the ADRENERGIC ANTAGONISTS and drugs that deplete norepinephrine or reduce the release of transmitters from adrenergic postganglionic terminals (see ADRENERGIC AGENTS). Drugs that act in the central nervous system to reduce sympathetic activity (e.g., centrally acting alpha-2 adrenergic agonists, see ADRENERGIC ALPHA-AGONISTS) are included here.
Prazosin
Anterior Hypothalamic Nucleus
Ganglia, Sympathetic
Receptors, N-Methyl-D-Aspartate
A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.
Diaphragm
The musculofibrous partition that separates the THORACIC CAVITY from the ABDOMINAL CAVITY. Contraction of the diaphragm increases the volume of the thoracic cavity aiding INHALATION.
Suramin
A polyanionic compound with an unknown mechanism of action. It is used parenterally in the treatment of African trypanosomiasis and it has been used clinically with diethylcarbamazine to kill the adult Onchocerca. (From AMA Drug Evaluations Annual, 1992, p1643) It has also been shown to have potent antineoplastic properties.
Colubridae
The largest family of snakes, comprising five subfamilies: Colubrinae, Natricinae, Homalopsinae, Lycodontinae, and Xenodontinae. They show a great diversity of eating habits, some eating almost anything, others having a specialized diet. They can be oviparous, ovoviviparous, or viviparous. The majority of North American snakes are colubrines. Among the colubrids are king snakes, water moccasins, water snakes, and garter snakes. Some genera are poisonous. (Goin, Goin, and Zug, Introduction to Herpetology, 3d ed, pp321-29)