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Pulmonary oedema produced by scorpion venom augments a phenyldiguanide‐induced reflex response in anaesthetized rats
Author(s) -
Deshpande S. B.,
Bagchi S.,
Rai O. P.,
Aryya N. C.
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.00537.x
Subject(s) - reflex , venom , anesthesia , pulmonary edema , medicine , pharmacology , chemistry , lung , biochemistry
1 The involvement of pulmonary oedema produced by scorpion venom in augmenting a phenyldiguanide (PDG)‐induced reflex response was evaluated in urethane‐anaesthetized rats. 2 PDG‐induced bradycardiac, hypotensive and apnoeic responses, expressed as time‐response area, exhibited similarities before or after venom treatment. Hence, the time‐response area of bradycardia was taken as a reflex parameter. Pulmonary oedema was determined by physical evaporation and histological methods. 3 Exposure to Indian red scorpion ( Buthus tamulus, BT; i.v.) venom for 30 min increased the pulmonary water content ( P < 0.05 ; Student's t test) and augmented the PDG‐induced bradycardiac reflex response by more than 2 times ( P < 0.001 ). The increase of pulmonary water content was maximal with 100 μg kg −1 of venom and the augmentation was maximal with 10 μg kg −1 . In a separate series of experiments, the venom (100 μg kg −1 )‐induced pulmonary oedema was confirmed by histological and physical methods. In this group also, the venom augmented the reflex to the same magnitude. 4 Pulmonary oedema (physical and histological) and augmentation of the bradycardiac reflex response after BT venom (100 μg kg −1 ; i.v.) were absent in animals pretreated with aprotinin, a kallikrein‐kinin inhibitor (6000 KIU; i.v.). 5 Ondansetron (10 μg kg −1 ; i.v.), a 5‐HT 3 receptor antagonist, failed to block the venom‐induced pulmonary oedema (physical and histological) but blocked the venom‐induced augmentation of the reflex. 6 The results of this study indicate that the venom‐induced augmentation of the PDG reflex is associated with pulmonary oedema involving kinins utilizing 5‐HT 3 receptors.