Reactivity and aggression in the rat: Induction by !a-adrenergic blocking agents injected ventral to anterior septum but not into lateral septum.

Abstract

Intracranial injections were made bilaterally through permanently implanted cannulas ending in the lateral septum or in the region ventral to the anterior septum. The rats were first screened with injections of a local anesthetic, lidocaine, which blocks both synaptic and axonal conduction. Those animals that showed an increase in reactivity and aggression were then injected with a synaptic transmitter blocking agent. Transmitter blocking agents reproduced the effect of the local anesthetic only in the region ventral to the anterior septum and that .alpha.-adrenergic (phentolamine, tolazoline), but not .beta.-adrenergic (propranolol, hydralazine), cholinergic (atropine, hyocine), or dopaminergic (haloperidol) blocking agents were effective. Synapses in the forebrain system controlling reactivity and aggression are probably .alpha.-adrenergic and are located in the region ventral to the anterior septum just lateral to the diagonal band of Broca. The septum itself may be involved only to the extent that it is traversed by fibers of passage.