Neural connections of the anterior hypothalamus and agonistic behavior in golden hamsters

In male golden hamsters, offensive aggression is regulated by an interactio n between arginine-vasopressin and serotonin at the level of the anterior h ypothalamus. The present studies were conducted to study a neural network u nderlying this interaction. The connections of the anterior hypothalamus we re examined by retrograde and anterograde tracing in adult male hamsters. S everal limbic areas were found to contain both types of tracing suggesting reciprocal connections with the anterior hypothalamus. Their functional sig nificance relating to the consummation of aggression was tested by comparin g neuronal activity (examined through quantification of c-fos-immunolabelin g) in two groups of animals. Experimental animals were sacrificed after att acking an intruder. Control animals were sacrificed after exposure to a woo dblock carrying the odor of an intruder that elicited behaviors related to offensive aggression without its consummation. An increased density of Fos- immunoreactivity was found in experimental animals within the medial amygda loid nucleus, ventrolateral hypothalamus, bed nucleus of the stria terminal is and dorsolateral part of the midbrain central gray. These data suggest t hat these areas are integrated in a neural network centered on the anterior hypothalamus and involved in the consummation of offensive aggression. Fin ally, c-fos-immunoreactivity was combined with labeling of serotonin and va sopressin neurons to identify sub-populations particularly associated with offensive aggression. Vasopressin neurons in the nucleus circularis and med ial division of the supraoptic nucleus showed increased neuronal activity i n the fighters, supporting their role in the control of offensive aggressio n, Copyright (C) 2000 S. Karger AG, Basel.