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 RESEARCH ARTICLE
Year : 2013  |  Volume : 45  |  Issue : 4  |  Page : 365-370

A study to investigate capsaicin-induced pressure response in vagotomized rats


Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Correspondence Address:
Shripad B Deshpande
Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh
India
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Source of Support: Supported by the grants from University Grants Commission (UGC), New Delhi and Indian Council of Medical Research (ICMR), New Delhi, Conflict of Interest: None


DOI: 10.4103/0253-7613.115019

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Objectives: Capsaicin is used to evoke pulmonary C reflexes and produces complex pressure responses along with apnea/tachypnea, and bradycardia. In the present study, the mechanisms involved in capsaicin-induced pressure responses were explored. Materials and Methods: Tracheal, jugular venous, and femoral artery cannulations were performed in anesthetized adult rats. Blood pressure, respiratory excursions, and electrocardiogram were recorded. Cardiorespiratory reflex changes evoked by jugular venous injection of capsaicin (10 μg/kg) were recorded in vagotomized and antagonist pretreated animals. Results: Capsaicin produced triphasic pressure response exhibiting immediate hypotension, intermediate recovery, and delayed hypotension. Time-matched respiratory changes showed apnea, bradypnea, and tachypnea, respectively. Bradycardia occurred at immediate and intermediate phases. After vagotomy, immediate hypotension was abolished; the intermediate recovery was potentiated as hypertensive response; and the delayed hypotension persisted. In case of respiration, the immediate bradypnea persisted and delayed tachypnea was abolished; while heart rate changes at immediate and intermediate phases were abolished. Antagonists of α1 -adrenoceptor (prazosin or terazosin, 0.5 mg/kg), β-adrenoceptor (propranolol, 1 mg/kg), AT 1 receptor (losartan, 10 mg/kg) and Ca 2+ channel (diltiazem, 1 mg/kg) failed to block the capsaicin-induced intermediate hypertensive response in vagotomized animals. Conclusions: These observations implicate the existence of mechanisms other than adrenergic, angiotensinergic, or Ca 2+ channel-dependent mechanisms for mediating the capsaicin-induced intermediate hypertensive response in vagotomized animals.






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