Coronary vasoconstriction during stimulation in hypothalamic defense region.

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Autonomic Nervous System

Background:

• Previous studies identified a lateral hypothalamus (LH) site eliciting coronary vasoconstriction via electrical stimulation.
• The neural pathways projecting to the LH site were investigated.

Purpose of the Study:

• To identify brain regions projecting to the lateral hypothalamus (LH) involved in coronary vasoconstriction.
• To investigate the role of the anterior hypothalamic area (AHA) in cardiovascular responses.

Main Methods:

• Retrograde tracer (Fast Blue) injections into the LH to map projections.
• Electrical stimulation of various brain regions (PVN, BNST, DRN, AHA) in anesthetized cats.
• Measurement of coronary vascular resistance (CVR) and hindquarter vascular resistance.
• Microinjection of excitatory amino acids into AHA.

Main Results:

• Projections to LH were identified from the paraventricular nucleus (PVN), bed nucleus of the stria terminalis (BNST), and dorsal raphe nucleus (DRN).
• Electrical stimulation of DRN and BNST did not increase CVR.
• Stimulation of the AHA, not retrogradely labeled, caused coronary vasoconstriction and hemodynamic changes resembling the defense reaction.
• The AHA response was attributed to fibers of passage, not local cell bodies.

Conclusions:

• Coronary vasoconstriction may be a component of the defense reaction.
• The anterior hypothalamic area (AHA) plays a role in eliciting coronary vasoconstriction, likely via activation of passing fibers.
• These findings implicate AHA in the central control of coronary circulation during stress responses.