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Histamine H3 receptor activation selectively inhibits dopamine D1 receptor-dependent [3H]GABA release from depolarization-stimulated slices of rat substantia nigra pars reticulata

1997; Elsevier BV; Volume: 80; Issue: 1 Linguagem: Inglês

10.1016/s0306-4522(97)00100-0

1873-7544

María de los Ángeles García, Benjamí­n Florán, José‐Antonio Arias‐Montaño, J.M. Young, Jorge Aceves,

Receptor Mechanisms and Signaling

The release of [3H]GABA from slices of rat substantia nigra pars reticulata induced by increasing extracellular K+ from 6 to 15 mM in the presence of 10 μM sulpiride was inhibited by 73±3% by 1 μM SCH 23390, consistent with a large component of release dependent upon D1 receptor activation. The histamine H3 receptor-selective agonist immepip (1 μM) and the non-selective agonist histamine (100 μM) inhibited [3H]GABA release by 78±2 and 80±2%, respectively. The inhibition by both agonists was reversed by the H3 receptor antagonist thioperamide (1 μM). However, in the presence of 1 μM SCH 23390 depolarization-induced release of [3H]GABA was not significantly decreased by 1 μM immepip. In rats depleted of dopamine by pretreatment with reserpine, immepip no longer inhibited control release of [3H]GABA, but in the presence of 1 μM SKF 38393, which produced a 7±1-fold stimulation of release, immepip reduced the release to a level not statistically different from that in the presence of immepip alone. Immepip (1 μM) also inhibited the depolarization-induced release of [3H]dopamine from substantia nigra pars reticulata slices, by 38±3%. The evidence is consistent with the proposition that activation of histamine H3 receptors leads to the selective inhibition of the component of depolarization-induced [3H]GABA release in substantia nigra pars reticulata slices which is dependent upon D1 receptor activation. This appears to be largely an action at the terminals of the striatonigral GABA projection neurons, which may be enhanced by a partial inhibition of dendritic [3H]dopamine release.