Baclofen and noradrenergic function in the rat frontal cerebral cortex

Possible changes in noradrenergic function were investigated in rat frontal cerebral cortex after acute treatment (1, 2 h) with the GABAB agonist, baclofen. A single i.p. injection of d,l-baclofen 10 mg/kg both reduced noradrenaline (NA) biosynthesis in vivo (31%) and the endogenous concentration of normetanephrine (NMN) (32%) and increased NA levels (28%). Increased [3H]NA uptake (15%) and [3H]dihydroxyphenyl-ethyleneglycol ([3H]DOPEG formation (39%) were observed in cortex slices ex vivo from baclofen-treated animals. The activity of monoamineoxidase (MAO) was unchanged after baclofen treatment. We suggest that baclofen might interfere in vivo with noradrenergic neurotransmission, reducing NA biosynthesis and release in the rat cerebral cortex.