Locus coeruleus noradrenergic lesions attenuate intraoral intake.

I.p. injections of DSP-4 in male rats decreased norepinephrine (NE) levels to varying degrees throughout the brain with 66.7% reductions in the hypothalamic paraventricular nucleus. Intake of intraorally infused sucrose was reduced for 14 days but daily pellet intake recovered within 5 days post-injection. Intraventricular NE restored intraoral sucrose intake in DSP-4-lesioned rats without affecting controls. Intraventricular infusion of neuropeptide Y (NPY) reduced intraoral intake in controls but had no effect in DSP-4-lesioned rats. NPY markedly inhibited intraoral intake in DSP-4-treated rats that also received NE. These data confirm studies showing that NPY decreases consummatory ingestive behavior and suggest that this inhibition involves ascending noradrenergic projections from locus coeruleus.