LOCUS-CERULEUS MODULATES MIGRATING MYOELECTRIC COMPLEX IN RATS

The role of the locus ceruleus (LC) in the control of migrating myoelectric complex (MMC) was investigated in rats with lesions induced by injections of 6-hydroxydopamine (6-OHDA). Control animals received the vehicle alone. MMC was recorded in conscious rats chronically fitted with electrodes. After 6-OHDA was injected into the LC, lesions of the LC were total, partial (mostly rostral), or ineffective. The MMC period was significantly longer in animals with a total or partial lesion but was unchanged in animals with an ineffective lesion. No lesion of other brain noradrenergic nuclei was observed. The longer MMC period is comparable to that obtained after intracerebroventricular injection of 6-OHDA, which is responsible for a more diffuse destruction of brain noradrenergic systems, including LC itself. Bilateral lesions of the central tegmental tract, which carries ascending noradrenergic axons from the medullary and pontine cell groups outside the LC, do not alter the MMC cycle. Consequently, the LC is most likely the major brain noradrenergic candidate for modulating the MMC pattern in rats.