Neurochemical correlates of behaviour. Changes in acetylcholine, norepinephrine and 5-hydroxytryptamine concentrations in several discrete brain areas of the rat during behavioural excitation.

Abstract

Abstract—Acetylcholine, 5‐hydroxytryptamine, and norepinephrine concentrations were measured in the telencephalon, diencephalon plus mesencephalon (midbrain), and pons‐medulla oblongata of rats exhibiting behavioral excitation while working on a Sidman avoidance schedule and injected with 50 mg/kg iproniazid 16 hr before being given 2 mg/kg tetrabenazine. Acetylcholine concentrations in all three brain areas decreased and returned to normal levels at different times. The time course of increased response rates correlated best with the acetylcholine levels in the telencephalon. Both the 5‐hydroxytryptamine and norepinephrine concentrations remained similar to the iproniazid control values during the period of behavioural excitation. However, the norepinephrine concentration in the midbrain showed a continuous decreasing trend toward naive control levels. These data suggest that changes in a cholinergic system in the telencephalon and a noradrenergic system in the midbrain operate in the maintenance of behavioural excitation.