Investigations About a Direct Neurotensin‐Dopamine Interaction by Nuclear Magnetic Resonance Study, Synaptosomal Uptake of Dopamine, and Binding of Neurotensin to Its Receptors

: Interactions between dopamine and neurotensin can occur at various levels of the dopaminergic pathways. By using different approaches in vitro, we investigated the proposed hypothesis that neurotensin might bind to dopamine in the synaptic cleft. Nuclear magnetic resonance spectra of neurotensin were not modified by the addition of dopamine, and no nuclear Overhauser effect was detected. Synaptosomal uptake of [3H]dopamine in the presence of neurotensin did not lead to any modifications of the kinetic constants of the uptake. Neurotensin binding was not modified by the addition of dopamine. These results did not confirm the suggestion that neurotensin can form a complex with dopamine.