Norepinephrine-mediated suppression of apomorphine-induced aggression and locomotor activity in the rat amygdala

The effect of injections of norepinephrine (NE)-depleting toxin DSP-4 into the central amygdala (AMY) on apomorphine-induced fighting (AIF) was studied. In addition, the influence of such treatment on related parameters such as spontaneous activity, pain sensitivity and changes in locomotion after (+)3-PPP or apomorphine (1 mg/kg SC each) were verified. Finally, injections of NE or phenylephrine into the AMY five min before AIF were performed. DSP-4 induced marked (-71%) and selective fall in NE within the AMY accompanied by significant increase in aggressive response to 5 mg/kg of apomorphine. DSP-4-treated animals were less active in the open field and more sensitive to pain in a hot plate test. They were also more responsive to locomotor-augmenting action of apomorphine. Significant suppression of AIF was seen after injections of NE and phenylephrine into the AMY. The results suggest that NE input to the AMY plays an inhibitory role in dopamine-related locomotion and aggressivity. Moreover, amygdalar NE appears to be involved in general activity and pain perception modulation.