Cardiovascular and respiratory effects induced by a purified scorpion toxin (tityustoxin) in unanesthetized rats.

Intravenous injection of a purified scorpion toxin (tityustoxin) into unanesthetized rats induced acute pulmonary edema, which was directly related to the dose and the time of intoxication. To study the cardiovascular and respiratory effects evoked by an edematogenic dose of the toxin (1 mg/kg), the following parameters were recorded in unanesthetized rats: systolic, diastolic and mean arterial pressure; central venous pressure; electrocardiogram; respiratory movements. The toxin induced acute systolic and diastolic hypertension, bradycardia and bradypnea. During a 1 hr period, the systolic, diastolic and mean arterial pressure fell progressively to control values, whereas the central venous pressure did not change significantly. The cardiac and respiratory rates remained lower than the control values during a 1 hr period. Several changes in the respiratory pattern were recorded, such as gasping, prolonged and labored expiration, ataxic rhythm and noisy inspiration with the mouth open. These respiratory changes were explained, in part, by the presence of edema in the lungs and froth in the trachea. From a group of 24 rats, 6 died 18-30 min after tityustoxin injection. The cause of death was apnea. The female rats were more susceptible to pulmonary edema and death than the male rats.