https://sites.oxy.edu/clint/physio/article/therewardcircuitlinkingprimateanatomyandhumanimaging.pdf

The reward circuit: linking primate anatomy and human imaging.

Disruption of the mouse dopamine transporter gene results in spontaneous hyperlocomotion despite major adaptive changes, such as decreases in neurotransmitter and receptor levels. In homozygote mice, dopamine persists at least 100 times longer in the extracellular space, explaining the biochemical basis of the hyperdopaminergic phenotype and demonstrating the critical role of the transporter in regulating neurotransmission. The dopamine transporter is an obligatory target of cocaine and amphetamine, as these psychostimulants have no effect on locomotor activity or dopamine release and uptake in mice lacking the transporter.

Hyperlocomotion and indifference to cocaine and amphetamine in mice lacking the dopamine transporter

Dopamine is a small and relatively simple molecule that fulfills diverse functions. Within the brain, it acts as a classical neurotransmitter whose attenuation or overactivity can result in disorders such as Parkinson’s disease and schizophrenia. Major advances in the cloning and characterization of biosynthetic enzymes, transporters, and receptors have increased our knowledge regarding the metabolism, release, reuptake, and mechanism of action of dopamine. Dopamine reaches the pituitary via hypophysial portal blood from several hypothalamic nerve tracts that are regulated by PRL itself, estrogens, and several neuropeptides and neurotransmitters. Dopamine binds to type-2 dopamine receptors that are functionally linked to membrane channels and G proteins and suppresses the high intrinsic secretory activity of the pituitary lactotrophs. In addition to inhibiting PRL release by controlling calcium fluxes, dopamine activates several interacting intracellular signaling pathways and suppresses PRL gene expression and lactotroph proliferation. Thus, PRL homeostasis should be viewed in the context of a fine balance between the action of dopamine as an inhibitor and the many hypothalamic, systemic, and local factors acting as stimulators, none of which has yet emerged as a primary PRL releasing factor. The generation of transgenic animals with overexpressed or mutated genes expanded our understanding of dopamine-PRL interactions and the physiological consequences of their perturbations. PRL release in humans, which differs in many respects from that in laboratory animals, is affected by several drugs used in clinical practice. Hyperprolactinemia is a major neuroendocrine-related cause of reproductive disturbances in both men and women. The treatment of hyperprolactinemia has greatly benefited from the generation of progressively more effective and selective dopaminergic drugs. (Endocrine Reviews 22: 724–763, 2001)

/pdf/dopamine-as-a-prolactin-prl-inhibitor-3xht7m3qq4.pdf

Dopamine as a prolactin (PRL) inhibitor.

The classical biogenic amine neurotransmitters — dopamine, noradrenaline, and 5-hydroxytryptamine — control a variety of functions including locomotion, autonomic function, hormone secretion, and the complex behaviours that are associated with affect, emotion and reward. A key step that determines the intensity and duration of monoamine signalling at synapses is the reuptake of the released transmitter into nerve terminals through high-affinity plasma membrane transporters. In recent years, molecular, pharmacological and genetic approaches have established the importance of monoamine transporters in the control of monoamine homeostasis and have provided insights into their regulation.

Plasma membrane monoamine transporters: structure, regulation and function

The medial prefrontal cortex in the rat: evidence for a dorso-ventral distinction based upon functional and anatomical characteristics.

Antibodies specific for the dopamine transporter (DAT) was developed and characterized by immunoblot analysis, immunoprecipitation, and immunocytochemistry, and used for immunolocalization of transporter protein in rat brain at the light microscopic level. Antibodies targeting the N-terminus, the second extracellular loop, and the C-terminus were generated from fusion proteins containing amino acid sequences from these respective regions. Immunoblot analysis demonstrated that N-terminus and loop antibodies were specific for expressed cloned DAT, recognized transporter protein in rat and human striatal membranes, and were sensitive to preabsorption with excess homologous fusion protein. Immunoprecipitation studies demonstrated that anti-DAT antisera recognized solubilized, radiolabeled DAT protein in a concentration-dependent manner. DAT immunocytochemistry with these antibodies were also sensitive to preabsorption with fusion protein and to lesions of dopaminergic mesostriatal and mesocorticolimbic pathways. Regional distribution of DAT coincided with established dopaminergic innervation of several regions, including ventral mesencephalon, medial forebrain bundle, and dorsal and ventral striatum. However, certain mismatches between immunocytochemical distributions of DAT and tyrosine hydroxylase were apparent, indicating that dopaminergic systems are heterogeneous and may use independent mechanisms for the regulation of dopamine levels in brain. The generation of specific DAT antibodies will permit further characterization of the cellular and subcellular localization of DAT protein, and of dopaminergic circuits in neurological and psychiatric disorders.

https://www.jneurosci.org/content/jneuro/15/3/1714.full.pdf

HB Niznik

Papers

The dopamine transporter: immunochemical characterization and localization in brain