John Neumeyer | Harvard University (original) (raw)
Papers by John Neumeyer
Journal of Pharmaceutical Sciences
British Journal of Pharmacology
Journal of Medicinal Chemistry
Journal of Pharmaceutical Sciences
Chemical Communications (London)
![Research paper thumbnail of Development of a high affinity and stereoselective photoaffinity label for the D-1 dopamine receptor: Synthesis and resolution of 7-[ 125I]iodo-8-hydroxy-3-methyl-1-(4′-azidophenyl)-2,3,4,5- tetrahydro-1H-3-benzazepine](https://attachments.academia-assets.com/54369905/thumbnails/1.jpg)
](Journal of Medicinal Chemistry
In an earlier paper, we reported the development of (*)-7-iodo-8-hydroxy-3-methyl-l-(4'-azidophen... more In an earlier paper, we reported the development of (*)-7-iodo-8-hydroxy-3-methyl-l-(4'-azidophenyl)-2,3,4,5tetrahydro-1H-3-benzazepine (I-MAB) and its '%I analogue ([ '%I]I-MAB) as selective, high affinity photoaffinity labels for the D-1 dopamine receptor. In this report, we now describe the complete synthesis and resolution of I-MAB and the pharmacological characterization of the stereoisomers in canine striatal membranes. R-(+)-I-MAB showed highly specific dopamine D-1 receptor binding (KD = 0.28 nM) and binds selectively and stereoselectively to the D-1 receptor. These results further confirm the previous suggestion that, in the benzazepine series of DA agonists and antagonists, the activity principally resides in the I?-(+) enantiomer, the S-(-) enantiomer being considerably less potent or inactive. Moreover, R-(+)-[12SI]I-MAB, upon photolysis, identifies the ligand-binding subunits of the neuronal D-1 receptor, with an apparent M , of 74 OOO, 62 OOO, and 51 OOO as assessed by autoradiography following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Photoincorporation of R-( +)-[12SI]I-MAB into these polypeptides was stereoselectively blocked by D-1 dopaminergic ligands with an appropriate pharmacologic profile for the receptor. R-(+)-[12SI]I-MAB should thus prove to be a useful stereoselective photoaffiiity label for the further characterization of the D-1 receptors. (3) Calne, D. B.; Larsen, T.
Molecular Pharmacology
Presynaptic autoreceptor-mediated modulation of dopamine (DA) synthesis was evaluated as the inhi... more Presynaptic autoreceptor-mediated modulation of dopamine (DA) synthesis was evaluated as the inhibition of tyrosine hydroxylase activity by enantiomeric mono- and dihydroxyaporphines with minced striatal tissue from rat brain. The isomers of N-n-propylnorapomorphine (NPA) both inhibited tyrosine hydroxylase activity [IC50 = 0.3 and 1.0 microM for (R)-(-)- and (S)-(+)-NPA, respectively; R/S potency = 3.6]. Their effects were fully blocked by the nonselective DA receptor antagonist fluphenazine, as well as by the D2-selective antagonist spiperone, but not by the D1 antagonist SCH-23390. These results suggest a D2-type autoreceptor-mediated inhibition of DA synthesis, with limited enantiomeric selectivity of this catechol-aporphine. The corresponding monohydroxy analogs, (R)-(-)- and (S)-(+)-11-hydroxy-N-n-propylnoraporphine (11-OH-NPa) were about 100 times less potent (IC50 = 42 and 87 microM, respectively) than the NPA isomers in fully inhibiting the enzyme activity in normal tissue but, after depletion of endogenous DA by acute in vivo pretreatment with reserpine (which did not alter the number of D1 or D2 specific binding sites), (R)-(-)-11-OH-NPa was a highly potent but partial agonist (IC25 = 7 nM). Fluphenazine and spiperone fully antagonized the inhibition of tyrosine hydroxylase by (R)-(-)-11-OH-NPa in reserpinized tissue, but SCH-23390 was ineffective. Actions mediated by endogenous DA probably contribute to the effect of high concentrations of (R)-(-)-11-Oh-NPa to evoke a full inhibition of DA synthesis, but its high potency partial agonist effects appear to be mediated by D2-autoreceptors. (S)-(+)-11-OH-NPa was a very weak partial agonist in reserpinized tissue, with an IC25 = 30 microM (essentially the same as normal tissue); thus, (R)-(-)-11-OH-NPa was greater than 4,000 times more potent than its S-(+)-enantiomer in the absence of endogenous DA. These results demonstrate that NPA, which contains a catechol moiety, acts as a full agonist to inhibit striatal DA synthesis via a presynaptic autoreceptor of the D2 type, with only slight stereoselectivity, and that its monohydroxy analog is a very potent but partial D2 autoreceptor agonist, with very high stereoselectivity.
Molecular Pharmacology
Alkyl and arylalkyl derivatives of the dopamine (DA) D2 antagonist spiperone were prepared and ch... more Alkyl and arylalkyl derivatives of the dopamine (DA) D2 antagonist spiperone were prepared and characterized chemically and pharmacologically. They included the N-methyl, N-phenethyl (NPS), and N-p-aminophenethyl (NAPS) derivatives, as well as the alkylating isothiocyanato (NIPS), bromacetamido, and ethylfumaramido p-substituted N-phenethylspiperones. These compounds showed high lipophilicity (log P up to 6.0 with NIPS), as well as very high in vitro D2 affinity (Ki = 35-280 pM) and D2 versus D1 selectivity (540-9000-fold) in radioreceptor assays with corpus striatum of rat brain. Of the alkylating series, NIPS showed the highest D2 affinity (57 pM) and D2 versus D1 selectivity (2040-fold) and so was selected for further evaluation. NPS, NAPS, and NIPS showed little or no affinity for 34 non-DA binding sites defined by radioligand assays for monoamine, amino acid, and peptide neurotransmitters, ion channels, peptide growth factors, and transmission mediators but did show low alpha 2 and moderate alpha 1 and 5-hydroxytryptamine (5-HT2) affinity with rat forebrain tissue in vitro; NIPS showed a marked gain in D2 versus 5-HT2 selectivity, compared with spiperone (1520- versus 26-fold). Systemic injections of NIPS induced marked decreases in rat striatal D2 binding sites 24 hr later, with little effect on D1, 5-HT2, or alpha 1 sites; NIPS and NAPS lowered apparent Bmax values at D2 receptors with little change in ligand affinity, ex vivo as well as in vitro. NPS, NAPS, and NIPS all induced dose-dependent lowering of D2 binding ex vivo (ID50 = 1-9 mumol/kg, intraperitoneally) and blocked the behavioral effects of the DA agonist apomorphine (0.9 mumol/kg) potently (ID50 = 0.3-0.5 mumol/kg) at 24 hr. Recovery from these anti-DA actions required about 1 week after equimolar (15 mumol/kg) and similarly effective doses of NPS and NAPS, as well as NIPS. Thus, highly selective and avidly bound lipophilic D2 affinity ligands with similarly avid in vitro and prolonged in vivo anti-DA activities can be derived from N-phenethylspiperones with or without an alkylating moiety present. Such affinity ligands may represent useful additions to previously used, generally less selective, D2 affinity ligands.
Klinische Wochenschrift
In experimental duodenal ulceration, dopamine levels, turnover, and binding sites are influenced.... more In experimental duodenal ulceration, dopamine levels, turnover, and binding sites are influenced. Dopamine agonists and antagonists exert anti- and proulcerogenic effect, respectively, probably by influencing duodenal hyper- or hypomotility, rather than effecting gastric secretion. The duodenal ulcerogenic effect of the dopamine neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) given to rats in multiple daily doses (p.o. or s.c.) also induced in a dose-dependent manner duodenal ulcers. Duodenal ulcers were prevented by pretreatment with dopamine agonists (e.g. bromocriptine, lergotrile) or monoamine oxidase inhibitors (e.g. pargyline or 1-deprenyl). Our hypothesis suggests that duodenal ulcerogens may interfere with the action of dopamine resulting in loss of the inhibitory function of dopamine, and producing tissue damage from the accumulated auto-oxidation products of dopamine. Alternatively a motility disorder induced by cysteamine, propionitrile or MPTP may contribute to the pathogenesis probably by involving localized hyperacidity in the duodenal bulb because of decreased neutralization and impaired duodenal emptying of acid.
Journal of Pharmacology and Experimental Therapeutics
ABSTRACT
The in vivo kinetics of the dopamine (DA) transporter probe 1 2 3 I-labeled 2r3-carboxymethoxy-3r... more The in vivo kinetics of the dopamine (DA) transporter probe 1 2 3 I-labeled 2r3-carboxymethoxy-3r3-(4iodophenyl)tropane ([1 2 3 1]r3-CIT) in striatum was investi gated with single-photon emission computerized tomog raphy (SPECT) in five healthy human subjects. The aim of this study was to derive an adequate measure of the DA transporter density that would not be affected by re gional cerebral blood flow or peripheral clearance of the tracer. SPECT data were acquired on the day of injection (day 1) from 0 to 7 h and on the following day (day 2) from 19 to 25 h. Arterial sampling on day 1 was used to mea sure the input function. Graphical, kinetic, and equilib rium analyses were evaluated. Graphical analysis of day 1 data, with the assumption of negligible dissociation of the tracer-receptor complex (k4 = 0), was found to be blood flow-dependent. A three-compartment kinetic analysis of day 1 data were performed using a three (k4 = 0)-and a four (k4 > O)-parameter model. The three-parameter 2[3-Carbomethoxy -3 [3-( 4-iodophenyl)tropane ([3-CIT; also referred to as RTI-55) is a potent cocaine analogue with a high affinity for the dopamine (DA) and serotonin (5-HT) transporters (Carroll et aI., 1991;. [ 1 23 I] [3_CIT has been shown to be a promising single-photon emission
ChemInform
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Pharmaceutical Sciences
British Journal of Pharmacology
Journal of Medicinal Chemistry
Journal of Pharmaceutical Sciences
Chemical Communications (London)
Journal of Medicinal Chemistry
In an earlier paper, we reported the development of (*)-7-iodo-8-hydroxy-3-methyl-l-(4'-azidophen... more In an earlier paper, we reported the development of (*)-7-iodo-8-hydroxy-3-methyl-l-(4'-azidophenyl)-2,3,4,5tetrahydro-1H-3-benzazepine (I-MAB) and its '%I analogue ([ '%I]I-MAB) as selective, high affinity photoaffinity labels for the D-1 dopamine receptor. In this report, we now describe the complete synthesis and resolution of I-MAB and the pharmacological characterization of the stereoisomers in canine striatal membranes. R-(+)-I-MAB showed highly specific dopamine D-1 receptor binding (KD = 0.28 nM) and binds selectively and stereoselectively to the D-1 receptor. These results further confirm the previous suggestion that, in the benzazepine series of DA agonists and antagonists, the activity principally resides in the I?-(+) enantiomer, the S-(-) enantiomer being considerably less potent or inactive. Moreover, R-(+)-[12SI]I-MAB, upon photolysis, identifies the ligand-binding subunits of the neuronal D-1 receptor, with an apparent M , of 74 OOO, 62 OOO, and 51 OOO as assessed by autoradiography following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Photoincorporation of R-( +)-[12SI]I-MAB into these polypeptides was stereoselectively blocked by D-1 dopaminergic ligands with an appropriate pharmacologic profile for the receptor. R-(+)-[12SI]I-MAB should thus prove to be a useful stereoselective photoaffiiity label for the further characterization of the D-1 receptors. (3) Calne, D. B.; Larsen, T.
Molecular Pharmacology
Presynaptic autoreceptor-mediated modulation of dopamine (DA) synthesis was evaluated as the inhi... more Presynaptic autoreceptor-mediated modulation of dopamine (DA) synthesis was evaluated as the inhibition of tyrosine hydroxylase activity by enantiomeric mono- and dihydroxyaporphines with minced striatal tissue from rat brain. The isomers of N-n-propylnorapomorphine (NPA) both inhibited tyrosine hydroxylase activity [IC50 = 0.3 and 1.0 microM for (R)-(-)- and (S)-(+)-NPA, respectively; R/S potency = 3.6]. Their effects were fully blocked by the nonselective DA receptor antagonist fluphenazine, as well as by the D2-selective antagonist spiperone, but not by the D1 antagonist SCH-23390. These results suggest a D2-type autoreceptor-mediated inhibition of DA synthesis, with limited enantiomeric selectivity of this catechol-aporphine. The corresponding monohydroxy analogs, (R)-(-)- and (S)-(+)-11-hydroxy-N-n-propylnoraporphine (11-OH-NPa) were about 100 times less potent (IC50 = 42 and 87 microM, respectively) than the NPA isomers in fully inhibiting the enzyme activity in normal tissue but, after depletion of endogenous DA by acute in vivo pretreatment with reserpine (which did not alter the number of D1 or D2 specific binding sites), (R)-(-)-11-OH-NPa was a highly potent but partial agonist (IC25 = 7 nM). Fluphenazine and spiperone fully antagonized the inhibition of tyrosine hydroxylase by (R)-(-)-11-OH-NPa in reserpinized tissue, but SCH-23390 was ineffective. Actions mediated by endogenous DA probably contribute to the effect of high concentrations of (R)-(-)-11-Oh-NPa to evoke a full inhibition of DA synthesis, but its high potency partial agonist effects appear to be mediated by D2-autoreceptors. (S)-(+)-11-OH-NPa was a very weak partial agonist in reserpinized tissue, with an IC25 = 30 microM (essentially the same as normal tissue); thus, (R)-(-)-11-OH-NPa was greater than 4,000 times more potent than its S-(+)-enantiomer in the absence of endogenous DA. These results demonstrate that NPA, which contains a catechol moiety, acts as a full agonist to inhibit striatal DA synthesis via a presynaptic autoreceptor of the D2 type, with only slight stereoselectivity, and that its monohydroxy analog is a very potent but partial D2 autoreceptor agonist, with very high stereoselectivity.
Molecular Pharmacology
Alkyl and arylalkyl derivatives of the dopamine (DA) D2 antagonist spiperone were prepared and ch... more Alkyl and arylalkyl derivatives of the dopamine (DA) D2 antagonist spiperone were prepared and characterized chemically and pharmacologically. They included the N-methyl, N-phenethyl (NPS), and N-p-aminophenethyl (NAPS) derivatives, as well as the alkylating isothiocyanato (NIPS), bromacetamido, and ethylfumaramido p-substituted N-phenethylspiperones. These compounds showed high lipophilicity (log P up to 6.0 with NIPS), as well as very high in vitro D2 affinity (Ki = 35-280 pM) and D2 versus D1 selectivity (540-9000-fold) in radioreceptor assays with corpus striatum of rat brain. Of the alkylating series, NIPS showed the highest D2 affinity (57 pM) and D2 versus D1 selectivity (2040-fold) and so was selected for further evaluation. NPS, NAPS, and NIPS showed little or no affinity for 34 non-DA binding sites defined by radioligand assays for monoamine, amino acid, and peptide neurotransmitters, ion channels, peptide growth factors, and transmission mediators but did show low alpha 2 and moderate alpha 1 and 5-hydroxytryptamine (5-HT2) affinity with rat forebrain tissue in vitro; NIPS showed a marked gain in D2 versus 5-HT2 selectivity, compared with spiperone (1520- versus 26-fold). Systemic injections of NIPS induced marked decreases in rat striatal D2 binding sites 24 hr later, with little effect on D1, 5-HT2, or alpha 1 sites; NIPS and NAPS lowered apparent Bmax values at D2 receptors with little change in ligand affinity, ex vivo as well as in vitro. NPS, NAPS, and NIPS all induced dose-dependent lowering of D2 binding ex vivo (ID50 = 1-9 mumol/kg, intraperitoneally) and blocked the behavioral effects of the DA agonist apomorphine (0.9 mumol/kg) potently (ID50 = 0.3-0.5 mumol/kg) at 24 hr. Recovery from these anti-DA actions required about 1 week after equimolar (15 mumol/kg) and similarly effective doses of NPS and NAPS, as well as NIPS. Thus, highly selective and avidly bound lipophilic D2 affinity ligands with similarly avid in vitro and prolonged in vivo anti-DA activities can be derived from N-phenethylspiperones with or without an alkylating moiety present. Such affinity ligands may represent useful additions to previously used, generally less selective, D2 affinity ligands.
Klinische Wochenschrift
In experimental duodenal ulceration, dopamine levels, turnover, and binding sites are influenced.... more In experimental duodenal ulceration, dopamine levels, turnover, and binding sites are influenced. Dopamine agonists and antagonists exert anti- and proulcerogenic effect, respectively, probably by influencing duodenal hyper- or hypomotility, rather than effecting gastric secretion. The duodenal ulcerogenic effect of the dopamine neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) given to rats in multiple daily doses (p.o. or s.c.) also induced in a dose-dependent manner duodenal ulcers. Duodenal ulcers were prevented by pretreatment with dopamine agonists (e.g. bromocriptine, lergotrile) or monoamine oxidase inhibitors (e.g. pargyline or 1-deprenyl). Our hypothesis suggests that duodenal ulcerogens may interfere with the action of dopamine resulting in loss of the inhibitory function of dopamine, and producing tissue damage from the accumulated auto-oxidation products of dopamine. Alternatively a motility disorder induced by cysteamine, propionitrile or MPTP may contribute to the pathogenesis probably by involving localized hyperacidity in the duodenal bulb because of decreased neutralization and impaired duodenal emptying of acid.
Journal of Pharmacology and Experimental Therapeutics
ABSTRACT
The in vivo kinetics of the dopamine (DA) transporter probe 1 2 3 I-labeled 2r3-carboxymethoxy-3r... more The in vivo kinetics of the dopamine (DA) transporter probe 1 2 3 I-labeled 2r3-carboxymethoxy-3r3-(4iodophenyl)tropane ([1 2 3 1]r3-CIT) in striatum was investi gated with single-photon emission computerized tomog raphy (SPECT) in five healthy human subjects. The aim of this study was to derive an adequate measure of the DA transporter density that would not be affected by re gional cerebral blood flow or peripheral clearance of the tracer. SPECT data were acquired on the day of injection (day 1) from 0 to 7 h and on the following day (day 2) from 19 to 25 h. Arterial sampling on day 1 was used to mea sure the input function. Graphical, kinetic, and equilib rium analyses were evaluated. Graphical analysis of day 1 data, with the assumption of negligible dissociation of the tracer-receptor complex (k4 = 0), was found to be blood flow-dependent. A three-compartment kinetic analysis of day 1 data were performed using a three (k4 = 0)-and a four (k4 > O)-parameter model. The three-parameter 2[3-Carbomethoxy -3 [3-( 4-iodophenyl)tropane ([3-CIT; also referred to as RTI-55) is a potent cocaine analogue with a high affinity for the dopamine (DA) and serotonin (5-HT) transporters (Carroll et aI., 1991;. [ 1 23 I] [3_CIT has been shown to be a promising single-photon emission
ChemInform
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.