title: Morphine blocks the Mesobuthus tamulus venom-induced augmentation of phenyldiguanide reflex and pulmonary edema in anesthetized rats.
abstract: OBJECTIVE
  Pulmonary edema, a manifestation of scorpion envenomation syndrome, is attributed to cardiogenic or noncardiogenic factors. Morphine is a drug used for cardiogenic pulmonary edema and its effect on Mesobuthus tamulus (MBT) venom-induced changes is not known. Therefore, we hypothesized that morphine blocks the MBT venom-induced augmentation of phenyldiguanide (PDG) reflex and pulmonary edema.
  
  
  METHODS
  Experiments were performed on anesthetized adult female rats. Trachea and jugular vein were cannulated, and the electrocardiographic potentials were recorded by connecting needle electrodes in limb lead II configuration. PDG (10 ΅g/kg, IV, bolus injection) responses were elicited by bolus injection initially, after saline/morphine (1 mg/kg) and after injecting MBT venom (100 μg/kg). The time-response area of the PDG-induced bradycardiac response after treatment was calculated as % of the initial PDG response area. At the end of experiments, lungs were excised for determination of pulmonary water content.
  
  
  RESULTS
  PDG produced bradycardiac response that lasted for >60 s. MBT venom augmented the PDG reflex response by 2.5 times. In morphine pretreated group, augmentation of bradycardiac response induced by MBT venom was absent. MBT venom increased the pulmonary water content, and the increase was absent in morphine pretreated animals.
  
  
  CONCLUSIONS
  The results reveal that morphine prevents the MBT venom-induced augmentation of PDG reflex response and pulmonary edema. Thus, morphine can be useful in scorpion envenomation syndrome associated with pulmonary edema.
authors.affiliation: Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
authors.forename: Aparna
authors.initials: A
authors.lastname: Akella
authors.affiliation: Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
authors.forename: Anil K
authors.initials: AK
authors.lastname: Tiwari
authors.affiliation: Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
authors.forename: Om P
authors.initials: OP
authors.lastname: Rai
authors.affiliation: Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
authors.forename: Shripad B
authors.initials: SB
authors.lastname: Deshpande
mesh_terms: D000818:Animals; D001645:Biguanides / Q000494:pharmacology*; D005260:Female; D009020:Morphine / Q000494:pharmacology*; D011654:Pulmonary Edema / Q000139:chemically induced / Q000517:prevention & control*; D051381:Rats; D012018:Reflex / Q000187:drug effects*; D012604:Scorpion Venoms / Q000037:antagonists & inhibitors* / Q000633:toxicity
chemical_list: D001645:Biguanides; D012604:Scorpion Venoms; D009020:Morphine; C008846:phenyl biguanide
keywords: Acute pulmonary edema; Indian red scorpion; J-reflex; cardiac arrest; opioids