Neurotensin and dopamine interactions.

Interactions between the classical monoamine neurotransmitter dopamine (DA) and the peptide neurotransmitter neurotensin (NT) in the central nervous system (CNS) have now been investigated for over two decades. Interest in this topic has been sustained, primarily because of the potential clinical relevance of these interactions to schizophrenia and drug abuse. In the past five years, important new discoveries in the NT field have markedly expanded our previous database. Additional NT receptors have been cloned, and novel and refined techniques have contributed to a more detailed description of the anatomy of the CNS NT system. Additionally, lipophilic NT receptor antagonists, active in the CNS after peripheral administration, have rendered more facile the investigation of the physiologic importance of endogenous NT at electrophysiologic, neurochemical, and behavioral levels. In the present review, the discussion of NT/DA interactions will progress from a discussion of the anatomical interactions between these two systems, to electrophysiologic and neurochemical interactions, and finally to behavioral implications-always with focus toward the potential clinical relevance of the data. The discussion of interactions between NT and DA systems will be limited to those occurring within the CNS. Moreover, because the DA projections from the midbrain to the striatum account for the bulk of the DA innervation in the CNS, we will focus on NT/DA interactions within these brain regions. Last, because of the extensive literature on NT/DA interactions available in the rat, our discussion will be based primarily on studies using this species.