Dopaminergic neurotransmission in somatodendritic and terminal areas of the rat brain: susceptibility to modulation by D1 and D2 receptors and to axotomy.

We have investigated the influence of D1 and D2 dopamine receptor active drugs on dopamine (DA) release in substantia nigra (SN), striatum and limbic forebrain in intact and in hemisected rats in vivo. DA release was indirectly assessed as 3-methoxytyramine (3-MT) accumulation following monoamine oxidase inhibition by pargyline. Hemisection per se had no effect on the 3-MT accumulation in the SN. Neither, had SCH 23390, SK & F 28393, or cis-flupentixol any effect in the SN in intact animals or in the lesioned side in hemisected animals. SCH 23390 slightly increased the 3-MT accumulation both in the striatum and limbic forebrain, indicating a stimulatory action on DA release, but SK & F 38393 had no effect in these brain regions. A difference between the striatum and the limbic forebrain was that the effects of SCH 23390, and cis-FPX were almost abolished following hemisection in the limbic forebrain, but only partially reduced in the striatum. In summary, our data give further support for the concept that neither D1 nor D2 dopamine receptors have any pronounced influence on the DA release in the SN. The data also indicate operational differences in the feedback regulation of limbic versus striatal dopaminergic transmission.