Fear-potentiated startle elevates catecholamine levels in the dorsomedial hypothalamus of rats.

The norepinephrine (NE), dopamine (DA), and serotonin (5-HT) systems are thought to be important in the development of anxiety and stress. The dorsomedial hypothalamus (DMH) of rats has been implicated in the regulation of physiological and behavioral responses associated with fear and anxiety. In order to elucidate the interactions between the monoamine systems and the DMH, we studied the effects of subjecting rats to the fear-potentiated startle test, a commonly used test of anxiety in rats, on the NE, DA, and 5-HT levels in the DMH. Rats in the potentiated startle test, but not those exposed to just foot shocks or acoustic startle, showed significantly higher levels of NE and DA in the DMH compared to cage controls. In contrast, foot shocks significantly elevated the 5-HT levels in the DMH.