title: Central beta-adrenoceptors mediate phasic and sustained components of hemodynamic responses to acute behavioral stress.
abstract: Startle elicits a pattern of cardiovascular responses that is consistent within individual rats but varies between rats. We examined the hypothesis that central beta-adrenoceptors mediate differences in the hemodynamic responses to stress. Conscious rats exposed to cold water (1 cm deep, 1 min) had an initial phasic (startle) response (first 5 s) that varied considerably between rats. We designated those rats with an initial increase in cardiac output (CO) and systemic vascular resistance (SVR) as mixed responders while those with only an increase in SVR were vascular responders. Propranolol pretreatment (3 microg, icv) made the phasic changes in CO more negative, whereas isoproterenol (3 microg) made the CO response more positive in mixed responders and attenuated the increases in arterial pressure and SVR in vascular responders. Metoprolol (30 microg, icv) depressed the change in CO due to startle in mixed responders by decreasing heart rate. ICI 188,551 (25 microg, icv) did not alter the responses to startle but depressed the heart rate and CO responses and enhanced the pressor and SVR responses to sustained stress (1 min exposure to cold water). The results suggest that startle elicits hemodynamic responses that are primarily dependent on beta1-adrenoceptors but responses to sustained stress are dependent on beta2-adrenoceptors in the CNS.
authors.affiliation: Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, 1402 S. Grand Boulevard, St. Louis, MO 63104, USA.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Rauls
authors.forename: Yun
authors.initials: Y
authors.lastname: Tan
authors.forename: Mark M
authors.initials: MM
authors.lastname: Knuepfer
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism*; D003080:Cold Temperature / Q000009:adverse effects; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology; D013312:Stress, Physiological / Q000503:physiopathology*; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014851:Wakefulness / Q000502:physiology
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; D011433:Propranolol; D008790:Metoprolol; D007545:Isoproterenol