title: A study to investigate capsaicin-induced pressure response in vagotomized rats.
abstract: OBJECTIVE
  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.
  
  
  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), AT1 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.
authors.affiliation: Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
authors.forename: Abhaya
authors.initials: A
authors.lastname: Dutta
authors.forename: Aparna
authors.initials: A
authors.lastname: Akella
authors.forename: Shripad B
authors.initials: SB
authors.lastname: Deshpande
mesh_terms: D058668:Adrenergic alpha-1 Receptor Antagonists / Q000627:therapeutic use; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use; D000818:Animals; D002121:Calcium Channel Blockers / Q000627:therapeutic use; D002211:Capsaicin; D004110:Diltiazem / Q000627:therapeutic use; D005260:Female; D006973:Hypertension / Q000139:chemically induced* / Q000188:drug therapy / Q000503:physiopathology*; D019808:Losartan / Q000627:therapeutic use; D011224:Prazosin / Q000031:analogs & derivatives / Q000627:therapeutic use; D011433:Propranolol / Q000627:therapeutic use; D051381:Rats; D014628:Vagotomy
chemical_list: D058668:Adrenergic alpha-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists; D047228:Angiotensin II Type 1 Receptor Blockers; D002121:Calcium Channel Blockers; C041226:Terazosin; D011433:Propranolol; D004110:Diltiazem; D019808:Losartan; D002211:Capsaicin; D011224:Prazosin
keywords: Adrenoceptor antagonist; capsaicin; diltiazem; losartan; prazosin; propranolol