Evidence that self-stimulation of the region of the locus coeruleus in rats does not depend upon noradrenergic projections to telencephalon.

Rats with intracranial self-stimulation (ICSS) electrodes in the locus coeruleus and adjacent pontine tegmental structures received stereotaxically placed bilateral injections of 6-hydroxydopamine (4 mug/2 mul) into the mesencephalic trajectory of the dorsal tegmental noradrenergic bundle. The consequent depletions of norepinephrine in the cerebral cortices and hippocampi (96.7%) did not result in significant changes in ICSS. Thus, diencephalic and telencephalic noradrenergic projections of the locus coeruleus do not appear to be critical for the occurrence of ICSS from that nucleus or its surrounding region. Nor do these projections appear to be crucially involved in the enhancement of this ICSS by D-amphetamine. Rats in this study showed two-fold increases in responding following injections of D-amphetamine sulfate (0.5 mg/kg) both before and after the lesions of the dorsal tegmental bundle. These results suggest that the ascending projections of the locus coeruleus are not critically involved in ICSS of the dorsal pontine tegmentum.