L-dopamine

Jiang, D., and Sibley, D. R. (1999) Regulation of D(l) dopamine receptors with mutations of protein kinase phosphorylation sites attenuation of the rate of agonist-induced desensitization. Mol. Pharmacol. 56, 675-683. 

Altropane and ioflupane bind L-dopamine transporter protein. They are being developed, respectively, as potential contrast agent for radioimaging and imaging... 

D-l Dopamine Receptor-Mediated Activation oi Adenylate Cyclase, cAMP Accumulation, and PTH Release in Dispersed Bovine Parathyroid Cells... 

It is very likely an inaccuracy to call the D-l dopamine receptor an enzyme. Because of the effects of guanine nucleotides on dopamine-stimulated adenylate cyclase, it is likely by analogy with other receptors (i.e. the 3 receptor) that the D-l receptor is a distinct molecular entity which is coupled to adenylate cyclase by a guanine nucleotide binding subunit. Proof of this point, of course, will require physical separation of these entities. 

Dopamine induces biochemical and physiological effects in the mammalian neostriatum. The occurrence of a D-l dopamine receptor (in the classification scheme of Kebabian and Caine) accounts for the ability of dopamine to enhance cyclic AMP formation. The occurrence of a D-2 dopamine receptor accounts for the ability of dopamine to inhibit cyclic AMP formation brought about by stimulation of a D-l dopamine receptor. Dopamine receptors mediate the regulation of (1) the release or turnover of acetylcholine (postsynaptic dopamine receptor) and (2) the release or turnover of dopar mine (presynaptic autoreceptor). Both receptors can be classified as D-2 dopamine receptors. Indications for the occurrence of dopamine receptors affecting the release or turnover of GABA, glutamate, serotonin and several neuropeptides are evaluated. 

An important criteria of D-l dopamine agonist activity is stimulation of dopamine-sensitive adenylate cyclase (8). Table I compares the activity of the four benzazepines and dopamine as stimulants of rat striatal adenylate cyclase. All of the benzazepines are only partial agonists with SK F 82526 and SK F 85174 being about 20 times more potent than dopamine and SK F 38393 and SK F 87516 being similar in potency to dopamine. 

The Auxiliary Binding Site and Selectivity for D-2 and D-l Dopamine Receptors... 

Zahrt J, Taylor JR, Mathew RG, Arnsten AFT. 1997b. Supra-normal stimulation of D-l dopamine receptors in the rodent prefrontal cortex impairs spatial working memory performance. J Neurosci 17 8528-8535. 

Flores-Hernandez J, Hernandez S, Snyder GL, Yan Z, Fienberg AA, Moss SJ, Greengard P, Surmeier DJ (2000) D(l) dopamine receptor activation reduces GABA(A) receptor currents in neostriatal neurons through a PKA/ DARPP-32/PP1 signaling cascade. J Neurophysiol 83 2996-3004. 

Jin LQ, Wang HY, Friedman E (2001) Stimulated D(l) dopamine receptors couple to multiple Galpha proteins in different brain regions. J Neurochem 75 981-990. 

Kimura K, White BH, Sidhu A (1995) Coupling of human D-l dopamine receptors to different guanine nucleotide binding proteins. Evidence that D-l dopamine receptors can couple to both Gs and G(o). J Biol Chem 270 14672-14678. 

Breese GR, Baumeister AA, Napier TC, Frye GD, Mueller RA (1985a) Evidence that D-l dopamine receptors contribute to the supersensitive behavioral responses induced by L-dihydroxyphenylalanine in rats treated neonatally with 6-hydroxydopamine. J Pharmacol Exp Ther 235 287-295. 

Breese GR, Napier TC, Mueller RA (1985b) Dopamine agonist-induced locomotor activity in rats treated with 6-hydroxydopamine at differing ages functional supersensitivity of D-l dopamine receptors in neonatally lesioned rats. J Pharmacol Exp Ther 234 447-455. 

Molloy AG, Waddington JL (1987) Assessment of grooming and other behavioural responses to the D-l dopamine receptor agonist SK F 38393 and its R- and S-enantiomers in the intact adult rat. Psychopharmacology (Berl) 92 164-168. 

Temlett JA, Chong PN, Oertel WH, Jenner P, Marsden CD (1988) The D-l dopamine receptor partial agonist, CY 208-243, exhibits antiparkinsonian activity in the MPTP-treated marmoset. Eur J Pharmacol 756 197-206. 

Koob GF, Le HT, Creese I (1987) The D-l dopamine receptor antagonist SCH-23390 increases cocaine self-administration in the fato Neurosci Lett 79 315-320. 

Parker SL, Crowley WR (1992) Activation of central D-l dopamine receptors stimulates oxytocin release in the lactating rat evidence for involvement of the hypothalamic paraventricular and supraoptic nuclei. Neuroendocrinology 56 385—392. 

Aromatic amino acids that originate from the shikimate pathway also act as precursors to many alkaloids. Alkaloids that contain a phenylethylamine moiety are derived from L-tyrosine or its oxidation product L-dihydroxyphenylalanine (L-DOPA). Mescaline (N7) originating from the latter amino acid is known to occur in several cacti and is responsible for the hallucinogenic activity of peyote (Lophophora williamsii, Cactaceae). Lophocerine is a tetrahydroisoquinoline alkaloid derived from L-dopamine and found to occur in a different Lophophora species, L. schotti. 

Another example is to be found in the drug therapy of Parkinson s disease. The use of L-dopa (levodopa) as a prodrug for dopamine has already been described. However, to be effective, large doses of L-dopa (3-8 g per day) are required, and over a period of time these dose levels lead to side-effects such as nausea and vomiting. L-Dopa is susceptible to the enzyme dopa decarboxylase and as a result, much of the L-dopa administered is decarboxylated to L-dopamine before it reaches the central nervous system (Fig. 8.21). 

The product is applied for the treatment of Parkinsonism that is caused by a lack of l-dopamine and its receptors in the brain. L-Dopamine is synthesized in organisms by decarboxylation of L-3,4-dihydroxyphenylalanine (L-dopa). Since L-dopamine cannot pass the blood-brain barrier L-dopa is applied in combination with dopadecarbox-ylase-inhibitors to avoid formation of L-dopamine outside the brain. Ajinomoto produces L-dopa by this lyase-biotransformation with suspended whole cells in a fed batch reactor on a scale of 250 t a-1. Much earlier, Monsanto has successfully scaled up the chemical synthesis of L-dopa (Fig. 19-38). 

L-dopamine Trinuclear Ru amine complex in zeolite Y Carbon paste [150]... 

Fig. 14.2. Electropherogram for three neurotransmitters- (l) dopamin (2) norepinepluine, and (3) epinephrine at diamond CE detector (reprinted from [10]).

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