Midbrain cholinergic mechanisms in elicitation of hypothalamic aggressive responses in cats.

1. Electrodes were implanted stereotaxically in the central gray, and the anterolateral regions of the hypothalamus, in chronically prepared cats. 2. The affective attack behaviour elicited on electrical stimulation of the hypothalamic and the midbrain regions was recorded in the caged animals. 3. Bilateral microinfusions of atropine sulphate were given in the central gray and the effect on the midbrain and the hypothalamic responses studied. 4. Cholinergic blockade by atropine sulphate raised the threshold of many of the components of attack behaviour obtained on stimulation of the central gray, and from the anterior hypothalamic regions. 5. Muscarinic receptors may be playing an important role in the central gray regions for the modulation of the aggressive responses from the hypothalamus.