tetrodotoxin and Hypotension

Topics: Action Potentials; Anesthesia, Local; Animals; Chemical Phenomena; Chemistry; Fishes, Poisonous; Foodborne Diseases; Humans; Hypotension; Hypothermia; Muscle, Smooth; Neuromuscular Junction; Respiration, Artificial; Respiratory Insufficiency; Tetrodotoxin; Vomiting

Antagonism of saxitoxin-and tetrodotoxin-induced lethality by 4-aminopyridine was studied in urethane-anesthetized guinea pigs instrumented for the concurrent recordings of medullary respiratory-related unit activities (Bötzinger complex and Nu. para-Ambiguus), diaphragmatic electromyogram, electrocorticogram, Lead II electrocardiogram, blood pressure, end-tidal CO2 and arterial O2/CO2/pH. The toxin (either saxitoxin or tetrodotoxin) was infused at a dose rate of 0.3 microgram/kg/min (i.v.) to produce a state of progressive cardiorespiratory depression. The animals were artificially ventilated when the magnitude of integrated diaphragm activities was reduced to 50% of control. Immediately after the disappearance of the diaphragm electromyogram, the toxin infusion was terminated, and 4-aminopyridine (2 mg/kg, i.v.) was administered. The therapeutic effect of 4-aminopyridine was striking in that the toxin-induced blockade of diaphragmatic neurotransmission, vascular hypotension, myocardial anomalies, bradycardia and aberrant discharge patterns of medullary respiratory-related neurons could all be promptly restored to a level comparable to that of control condition. The animals were typically able to breathe spontaneously within minutes after 4-aminopyridine. At the dose level used to achieve the desired therapeutic responses, 4-aminopyridine produced no sign of seizure and convulsion. Although less serious side-effects such as cortical excitant/arousal and transient periods of fascicular twitch could be observed, these events were of minor concern, in our opinion, particularly in view of the remarkable therapeutic effects of 4-aminopyridine.

Topics: 4-Aminopyridine; Animals; Blood Gas Analysis; Blood Pressure; Bradycardia; Carbon Dioxide; Diaphragm; Electrocardiography; Electromyography; Electrophysiology; Guinea Pigs; Hydrogen-Ion Concentration; Hypotension; Infusions, Intravenous; Male; Neurons; Oxygen Consumption; Saxitoxin; Synaptic Transmission; Tetrodotoxin

The effect of tetrodotoxin-induced hypotension on intracranial pressure (ICP) was investigated in cats with normal and artificially increased ICP. Cats were anesthetized with intraperitoneal pentobarbital (25-30 mg/kg), intubated, and ventilated with nitrous oxide in oxygen. Mean arterial pressure (MAP), heart rate (HR), and pulmonary arterial pressure (PAP) were continuously recorded. A double 18-gauge needle was inserted into the cisterna magna; ICP was continuously monitored from one needle and the other was used to increase and maintain ICP at 27 +/- 4 mm Hg by infusion of pH-adjusted Ringer's lactate solution. After control measurements were taken, tetrodotoxin (TTX) was given intravenously in each cat when ICP was normal and increased. Injection of 8-16 micrograms TTX (approximately equal to 2-4 micrograms/kg) decreased MAP 40-50% for 8-12 min under both initial ICP conditions. Whether initial ICP was normal or elevated, no significant increase occurred in ICP (0.6 to 1 mm Hg), and cerebral perfusion pressure (CPP) was not jeopardized. When initial ICP was normal, TTX caused a decrease in HR that was statistically but not clinically significant. The change in HR when initial ICP was increased was not statistically or clinically significant. No significant change in PAP was apparent during TTX-hypotension under either initial ICP condition.

Topics: Anesthesia, General; Animals; Blood Pressure; Cats; Female; Heart Rate; Hypotension; Intracranial Pressure; Male; Pulmonary Wedge Pressure; Tetrodotoxin; Time Factors

Topics: Animals; Atropine; Female; Fibrinogen; Fibrinolysin; Guinea Pigs; Hypotension; Kinins; Male; Molecular Weight; Muscle Contraction; Muscle, Smooth; Peptides; Rats; Scopolamine; Tetrodotoxin

Topics: Animals; Blood Pressure; Blood Vessels; Cats; Dilatation; Electric Stimulation; Female; Heart Rate; Hindlimb; Hypotension; Lumbosacral Plexus; Male; Muscle, Smooth; Perfusion; Pressure; Species Specificity; Tetrodotoxin; Vasomotor System

Topics: Animals; Anura; Chromatography, Gel; Chromatography, Thin Layer; Dialysis; Hypotension; Mice; Panama; Tetrodotoxin; Toxins, Biological; Ventricular Fibrillation

Topics: Adrenal Medulla; Animals; Blood Pressure; Bradycardia; Cardiac Output; Cardiovascular System; Cats; Electrocardiography; Heart; Heart Rate; Hypotension; In Vitro Techniques; Neural Conduction; Respiration; Tetrodotoxin; Vagus Nerve; Vascular Resistance

Topics: Animals; Blood Pressure; Cats; Dogs; Hypotension; Muscles; Paralysis; Peripheral Nerves; Respiration; Respiratory Insufficiency; Tetrodotoxin; Toxins, Biological

Topics: Action Potentials; Animals; Blood Pressure Determination; Cats; Cerebellar Cortex; Cerebral Cortex; Electrophysiology; Evoked Potentials; Hypotension; Peripheral Nerves; Reflex; Respiration; Spinal Cord; Spinal Nerves; Tetrodotoxin; Toxins, Biological; Vasomotor System

Topics: Animals; Axons; Blood Pressure; Hypotension; Male; Rats; Sensory Receptor Cells; Spinal Cord; Tetrodotoxin; Toxins, Biological; Vagotomy

Topics: Animals; Antitoxins; Hypotension; Nerve Tissue; Neurotoxins; Nictitating Membrane; Paralysis; Tetrodotoxin; Toxins, Biological