Effect of locus coeruleus lesion on c-fos expression in the cerebral cortex caused by yohimbine injection or stress

The injection of the α-2 adrenoceptor antagonist, yohimbine, has been shown to increase c-fos immunoreactivity in the rat cerebral cortex. To determine the extent to which this response is mediated by the central noradrenergic system, the present studies examined it in rats previously given unilateral 6-OHDA lesions of the locus coeruleus. The lesions were found to produce a significant attenuation of the response. A similar effect on the c-fos immunoreactive response to restraint stress was found. It is concluded that the noradrenergic system plays a necessary role in the above c-fos responses in the cortex to yohimbine and to stress. The c-fos protein therefore appears to be involved in the effects of noradrenergic neurotransmission in the CNS.