Dopamine modulation evidence

Meiergerd SM, Patterson TA, Schenk JO (1993) D2 receptors may modulate the function of the striatal transporter for dopamine kinetic evidence from studies in vitro and in vivo. J Neurochem 61 764-7... 

Even more sophisticated control of neurotransmitter release is suggested by the possibility of heteroceptors . These receptors are thought to be located on the terminals of, and to modulate transmitter release from, one type of neuron, but are activated by transmitter released from a different type of neuron (Laduron 1985). For example, noradrenaline has been proposed to modulate release of a wide range of transmitters (e.g. dopamine, 5-HT and glutamate) through activation of a2-heteroceptors on the terminals of each of these different types of neuron. However, one factor that should be borne in mind is that most of the evidence for heteroceptors comes from studies of... 

Another potential clinical application of potent, peripherally acting DA agonists is the lowering of intraocular pressure in, for example, glaucoma [18]. There is in vivo and in vitro evidence that dopamine receptors might modulate the intraocular pressure. The influence of both agonists and antagonists for D1 and D2 receptors has been studied. Some human data are also available [19]. 

Both clinical and experimental studies have provided evidence that 5-HT can also regulate dopamine turnover. Thus several investigators have shown that a positive correlation exists in depressed patients between the homovaniUic acid (HVA), a major metabolite of dopamine, and 5-HIAA concentrations in the CSF. In experimental studies, stimulation of the 5-HT cell bodies in the median raphe causes reduced firing of the substantia nigra where dopamine is the main neurotransmitter. There is thus convincing evidence that 5-HT plays an important role in modulating dopaminergic... 

D2-like receptors couple mainly to Gi/o proteins, as mentioned above. However, there is no direct evidence to support this coupling for the release-modulating autoreceptors. Moreover, the subsequent intracellular signal transduction has never been studied directly in axon terminals. Mouse AtT-20 pituitary cells, which release acetylcholine and adrenocorticotropic hormone, have been used as a model for axon terminals. When expressed in these cells, D3 receptors mediated inhibition of P/Q-type calcium channels and activation of G protein-coupled inward rectifier potassium channels (Kuzhikandathil et al. 1998 Kuzhikandathil and Oxford 1999). Both would explain the autoreceptor-mediated inhibition of dopamine exocytosis. 

Like presynaptic dopamine autoreceptors, presynaptic histamine autoreceptors are activated by the released endogenous transmitter to inhibit further histamine release, as shown by the increase in histamine release caused by antagonists at H3 receptors a definite piece of physiology. Evidence has been presented recently that cardiac postganglionic sympathetic neurons of the guinea pig synthesize and release histamine as a co-transmitter (Li et al. 2003 2006). These noradrenaline-histamine neurons possess H3 autoreceptors which, when activated, depress the release of both noradrenaline and histamine - unlike the D2-like autoreceptors of dopamine-neurotensin neurons which modulate the release of the two cotransmitters in opposite direction (see Section 2.2). It would be of interest to see whether, conversely, activation of ot2-autoreceptors inhibits the release of histamine in the guinea pig heart. 

Driessen B, Bultmann R, Goncalves J, Starke K (1996) Opposite modulation of noradrenaline and ATP release in guinea pig vas deferens through prejunctional (l-adrenoccptors evidence for the P2 subtype. Naunyn-Schmiedeberg s Arch Pharmacol 353 564-71 Drukarch B, Stoof JC (1990) D2 dopamine autoreceptor selective drugs do they really exist Life Sci 47 361-76... 

Sarhan H, Grimaldi B, Hen R, Fillion G (2000) 5-HTib receptors modulate release of [3H] dopamine from rat striatal synaptosomes further evidence using 5-HT moduline, polyclonal 5-HT is receptor antibodies and 5-HT ib receptor knock-out mice. Naunyn Schmiedebergs Arch Pharmacol 361 12-18... 

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