Inhibition of the cardiovascular response to stress by systemic 5-HT1A activation: sympathoinhibition or anxiolysis?

Am J Physiol Regul Integr Comp Physiol. 2009 Aug;297(2):R495-501. doi: 10.1152/ajpregu.00232.2009. Epub 2009 Jun 10.

Abstract

5-HT(1A) agonists given systemically are known to produce anxiolytic effects. In addition, a growing body of research is showing that those compounds also have central sympathoinhibitory properties. Since emotional arousal gives rise to sympathetic activation, it is not clear whether systemic treatment with a 5-HT(1A) agonist reduces the sympathetic response to emotional stress primarily by a direct action on sympathetic-related sites in the brain or indirectly through reducing anxiety. To test this, we compared the effect of intraperitoneal injections of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.05 and 0.25 mg/kg), a preferential 5-HT(1A) agonist, or vehicle on the cardiovascular responses to four stressors known to produce sympathetic activation, three being emotional stressors, and one physiological. In conscious rats, 30-min exposure to either a neutral context, a fear-conditioned context, or to restraint stress led to increases in heart rate and blood pressure, which were attenuated by 8-OH-DPAT. In contrast, the same treatment did not reduce the cardiovascular response to 30-min cold exposure (4 degrees C). The results suggest that 8-OH-DPAT acts preferentially on limbic, rather than central, autonomic sites. Hence, doses of 5-HT(1A) agonists, which are just sufficient to produce anxiolysis, are not enough to cause true sympathoinhibition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 8-Hydroxy-2-(di-n-propylamino)tetralin / pharmacology
  • Animals
  • Anxiety / physiopathology
  • Anxiety / prevention & control*
  • Blood Pressure / drug effects
  • Blood Pressure / physiology
  • Body Temperature / physiology
  • Cardiovascular Physiological Phenomena / drug effects*
  • Cold Temperature
  • Exploratory Behavior / drug effects
  • Exploratory Behavior / physiology
  • Fear / physiology
  • Freezing Reaction, Cataleptic / drug effects
  • Freezing Reaction, Cataleptic / physiology
  • Heart Rate / drug effects
  • Heart Rate / physiology
  • Male
  • Motor Activity / drug effects
  • Motor Activity / physiology
  • Rats
  • Rats, Wistar
  • Receptor, Serotonin, 5-HT1A / physiology
  • Restraint, Physical / physiology
  • Serotonin 5-HT1 Receptor Agonists*
  • Stress, Physiological / drug effects*
  • Stress, Physiological / physiology
  • Stress, Psychological / physiopathology
  • Stress, Psychological / prevention & control*
  • Sympathetic Nervous System / drug effects*
  • Sympathetic Nervous System / physiology

Substances

  • Serotonin 5-HT1 Receptor Agonists
  • Receptor, Serotonin, 5-HT1A
  • 8-Hydroxy-2-(di-n-propylamino)tetralin