Related Experiment Videos
Central nervous effects of the convulsant protein canatoxin
Abstract:
Some pharmacological-toxicological effects of canatoxin, a toxic protein purified from the seeds of Canavalia ensiformis have been studied in mice and rats. The most obvious effect, a lethal tonic convulsion, was generally produced 10-15 min. after intravenous injection of 2-3 mg/kg of the highly purified protein (mol. wt. 88,000). After intraperitoneal, intramuscular or subcutaneous administration the convulsion produced by the same toxin dosis occurred within 24 hours. A spinal transection at the midthoracic level did not abolish the convulsions of the hindlimbs while destruction of the medulla below this level completely blocked the convulsions of the hindlimbs. The convulsions of the head and forelimbs were unaffected by these surgical pretreatments. The toxic protein did neither affect the isolated skeletal muscle nor did it potentiate nerve impulse induced contractions. The convulsive effect of canatoxin was potentiated by reserpine and attenuated by phenobarbital, diazepam, methenesine and also by haloperidol and spiroperidol. The total concentration of brain and spinal cord neurotransmitters seemed to remain unchanged after subconvulsive and convulsive doses of canatoxin. In the conscious rat the toxic protein did not change the blood pressure except for a shortlasting hypertensive response observed immediately before the onset of the convulsions. The heart frequency was lowered at subconvulsive and convulsive doses but no effect was seen on the frequency of the rat isolated right atria exposed to high doses of canatoxin. The body temperature was lowered by a convulsive doses of the toxic protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Canatoxin, a toxic protein from Canavalia ensiformis seeds, induces lethal tonic convulsions in rodents. Its neurotoxic effects appear to originate from the brainstem and spinal cord, not peripheral nerves.
Area of Science:
- Pharmacology
- Toxicology
- Neuroscience
Background:
- Canatoxin is a toxic protein isolated from Canavalia ensiformis seeds.
- Understanding its pharmacological and toxicological effects is crucial.
Purpose of the Study:
- To investigate the pharmacological and toxicological effects of canatoxin in mice and rats.
- To determine the mechanism of canatoxin-induced convulsions.
Main Methods:
- Intravenous, intraperitoneal, intramuscular, and subcutaneous administration of canatoxin.
- Surgical interventions including spinal transection and medullary destruction.
- Electrophysiological studies on isolated skeletal muscle and nerve.
- Assessment of drug interactions and neurotransmitter concentrations.
- Monitoring of physiological parameters like blood pressure, heart rate, and body temperature.
Main Results:
- Canatoxin induced lethal tonic convulsions, primarily affecting hindlimbs after spinal transection, suggesting a central nervous system origin.
- The toxic protein did not directly affect skeletal muscle or neuromuscular transmission.
- Convulsive effects were modulated by various drugs, including potentiation by reserpine and attenuation by phenobarbital, diazepam, and others.
- No significant changes in brain and spinal cord neurotransmitter concentrations were observed.
- Canatoxin caused transient hypertension, decreased heart rate, and lowered body temperature.
Conclusions:
- Canatoxin's primary toxic effect is a central nervous system-mediated tonic convulsion.
- The mechanism involves the brainstem and spinal cord, not peripheral neuromuscular junctions.
- Further research into canatoxin's specific molecular targets and pathways is warranted.