Effect of stimulation of locus coeruleus on the evoked potential in the amygdala in rats

Effects of stimulation of the locus coeruleus (LC) on evoked potential in the medial amygdala elicited by stimulation of the olfactory bulb (OB-AME potentials) were studied in the gallamine-immobilized rats. The amplitude of the OB-AME potential was inhibited 27.5% by the conditioning stimulation of LC delivered 30 msec before the test stimulation. The inhibitory effect of LC was reduced by propranolol 5 mg/kg i.p., but not by phentolamine 10 mg/kg i.p.. This effect was also reduced by tetrabenazine 10 mg/kg i.p.. Methamphetamine 5 mg/kg i.p. produced considerable potentiation of the LC inhibitory effect and a reduction of the OB-AME potential itself. These results suggest that the LC plays an inhibitory role in the electrical activity of the medial amygdala.