The role of norepinephrine in feeding behavior.

When dopamine-beta-hydroxylase is inhibited with FLA-63 (10 mg/kg) free feeding behavior is disrupted in satiated rats. While the average number of meals taken was not different from vehicle injected controls, meal size was decreased 58% in the first 9 hr after treatment with FLA-63. In starved animals, FLA-63, when given alone, produced little effect on feeding behavior, even though norepinephrine depletion was in excess of 40%. When given in combination with RO4-1284 (5 mg/kg), a vesicular reuptake inhibitor, feeding was reduced to 16% of control intake and norepinephrine was specifically depleted 99%. Feeding was reliably reinstated in animals which received FLA-63 plus RO4-1284 with either dl-threo-DOPs, a metabolic precursor to NE, or direct intrahypothalamic injections of NE. These findings suggest that the feeding inhibition observed after treatment with FLA-63 plus RO4-1284 is due to disruption of transmission in brain NE systems. A non-anorectic dosage of L110-140 (3.73 mg/kg), a specific FLA-63. Taken collectively, these findings suggest that the primary role of NE in feeding is maintenance of the consummatory response and that these effects are expressed in relation to activity in other neurochemical systems.