Increased shock-induced fighting with supersensitive beta-adrenergic receptors

Area of Science:

• Neuropharmacology
• Behavioral Neuroscience

Background:

• Haloperidol is known to suppress fighting behavior.
• The effects of chronic beta-adrenergic receptor antagonist administration on aggression are not fully understood.

Purpose of the Study:

• To investigate the long-term effects of chronic haloperidol and propranolol administration on shock-induced fighting in rats.
• To examine the relationship between chronic beta-blocker treatment, beta-adrenergic receptor density, and aggressive behavior.

Main Methods:

• Adult male rats were chronically treated with haloperidol or propranolol.
• Shock-induced fighting behavior was assessed.
• Beta-adrenergic receptor Bmax was measured in brain tissue.

Main Results:

• Chronic haloperidol suppressed fighting.
• Chronic propranolol (but not acute administration) facilitated fighting.
• Chronic administration of d,l-propranolol, l-propranolol, and pindolol increased fighting and beta-adrenergic receptor Bmax.
• D-propranolol and metoprolol did not alter fighting behavior or receptor density.

Conclusions:

• Chronic administration of certain beta-adrenergic receptor antagonists leads to an increase in shock-induced fighting in rats.
• This facilitation of fighting behavior is associated with an upregulation of beta-adrenergic receptors.
• The findings suggest a compensatory mechanism involving increased beta-adrenergic receptor sensitivity to endogenous norepinephrine.