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

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. The results showed that 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. These results suggest that synapses in the forebrain system controlling reactivity and aggression are alpha-asrenergic 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.