Fig. (4).

Schematic diagram depicts specificity of cytokine modulation of defensive rage behavior. Shown in this diagram are the reciprocal excitatory relationship between the medial hypothalamus (MH) and periaqueductal gray (PAG) in the expression of defensive rage behavior. The reciprocal inhibitory connections between the MH and lateral hypothalamus (LH) are presented in this diagram in order to illustrate the relationships of the defensive rage pathways to those associated with predatory attack. Powerful facilitation of defensive rage from MH is mediated through IL-1 type I and 5-HT₂ receptor mechanisms. A similar mechanism exists in the PAG as well. Suppression of defensive rage within MH is mediated through IL-2 and GABA_A receptor mechanisms. However, IL-2 in the PAG potentiates defensive rage behavior and this potentiating phenomenon is mediated through IL-2 and substance P – NK₁ mechanisms. (Modified from Zalcman and Siegel [103]).