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Biomedical subjects

T A Pugsley

Publications and source records attributed to T A Pugsley.

At least 19 recordsLinked to original sources

Lack of involvement of haloperidol-sensitive sigma binding sites in modulation of dopamine neuronal activity and induction of dystonias by antipsychotic drugs.

The present studies evaluated previous suggestions that haloperidol-sensitive sigma binding sites are involved in the modulation of dopamine (DA) neuronal activity and in the induction of the dystonic effects of antipsychotic drugs. These issues were addressed by evaluating the effects of compounds that have differing affinities for sigma binding sites, on the firing activity of DA neurons in the substantia nigra in chloral hydrate-anesthetized rats and on the ability to induce extrapyramidal motor dysfunction in squirrel monkeys sensitized to the dystonic effects of haloperidol. The agents studied included haloperidol, DTG (1,3-di-o-tolylguanidine), (+)-pentazocine, (+)-SKF 10,047, BMY 14802, 8-OH-DPAT and sulpiride. There was no relationship between affinity for sigma binding sites and the ability to either alter DA neuronal activity or to induce extrapyramidal motor dysfunction.

Animals

Pharmacological characterization of PD 118717, a putative piperazinyl benzopyranone dopamine autoreceptor agonist.

PD 118717 (7-[3-[4-(2-pyrimidinyl)-1-piperazinyl]-propoxy]-2H-1- benzopyran-2-one sulfate) proved to be a dopamine (DA) D-2 autoreceptor agonist in biochemical and electrophysiological studies in rats and to exhibit an antipsychotic-like profile in behavioral tests in rodents and monkeys. In vitro binding studies indicated that PD 118717 bound selectively to DA D-2 vs. D-1 receptors and exhibited agonist binding properties (biphasic inhibitory curves and GTP shift) similar to DA. It also had significant affinity for serotonin-(5-HT)1A but not 5-HT1B and 5-HT2 receptors. PD 118717 was active in antagonizing the tau-butyrolactone-induced accumulation of dopa in rat striatum and mesolimbic regions. PD 118717 also depressed the firing of DA neurons in substantia nigra pars compacta of rats. In both of the latter tests the effects of PD 118717 were reversed by haloperidol. PD 118717 decreased brain DA metabolism, decreased DA utilization, decreased accumulation of dopa after inhibition of L-aromatic amino acid decarboxylase, stimulated serum corticosterone and inhibited stimulated serum prolactin levels. PD 118717 did not alter striatal acetylcholine levels; nor did it induce locomotor stimulation or stereotypy in normal animals, suggesting a lack of postsynaptic DA stimulation of normosensitive DA receptors. In tests designed to reveal even weak postsynaptic DA agonist effects, PD 118717 stimulated locomotor activity in 6-hydroxydopamine-lesioned animals and relatively higher doses induced a low degree of stereotyped behavior when combined with the DA D-1 agonist SKF 38393. PD 118717 decreased the accumulation of 5-hydroxytryptophan in brain, an effect probably due to an agonist action at 5-HT1A receptors. PD 118717 decreased spontaneous locomotor activity in rodents, antagonized amphetamine-stimulated hyperactivity in mice and inhibited Sidman avoidance in monkeys, effects seen with antipsychotic agents. Unlike DA antagonist antipsychotics, PD 118717 did not induce extrapyramidal dysfunction in monkeys. PD 118717 displayed behavioral activity after p.o. dosing and its effects did not show tolerance on repeated dosing. In conclusion, PD 118717 has the profile of a DA autoreceptor agonist in neurochemical and neurophysiological tests and produces effects suggestive of antipsychotic efficacy without neurological side effect liability in preclinical behavioral tests.

Animals

Dopamine autoreceptor agonists as potential antipsychotics. 2. (Aminoalkoxy)-4H-1-benzopyran-4-ones.

The synthesis and pharmacological properties of a novel type of [(arylpiperazinyl)alkoxy]-4H-1-benzopyran-4-ones with dopaminergic activity are described. The nature of the arylpiperazine (AP) moiety determines the dopamine (DA) agonist/antagonist character of this series of compounds; when the aryl portion of the AP is unsubstituted the compounds appear to be DA autoreceptor agonists while substituted aryl groups seem to impart DA antagonist activity. A heterocyclic piperazine, 7-[3-[4-(2-pyridinyl)-1-piperazinyl]propoxy]-4H-1-benzopyran-4-one (31, PD 119819) has been identified as an extremely selective DA autoreceptor agonist in tests that include [3H]haloperidol binding, inhibition of spontaneous locomotor activity, inhibition of brain DA synthesis, inhibition of brain DA neuronal firing, stereotypy assessment, and reversal of 6-hydroxydopamine (6-OHDA) induced akinesia in rats. In addition, 31 possesses good oral activity in the Sidman avoidance test in squirrel monkeys, a predictor of clinical antipsychotic efficacy. In another primate model, 31 has been found to lack the liability for extrapyramidal side effects observed with currently available antipsychotic drugs.

Animals

Calcium channel blocking and positive inotropic activities of ethyl 5-cyano-1,4-dihydro-6-methyl-2-[(phenylsulfonyl)methyl]-4-aryl-3- pyridine-carboxylate and analogues. Synthesis and structure-activity relationships.

The synthesis and pharmacological evaluation of a series of 2-[(arylsulfonyl)methyl]-4-aryl-5-cyano-1,4-dihydropyridine-3-carboxylic acid esters and analogues are described. These compounds possess a unique profile namely, calcium channel blocking and positive inotropic activities in vitro. Compound 54 was selected as the best compound in the series and was studied in detail. The synthesis and biological profiles of enantiomers of 54 are also reported. The data indicate that although the calcium channel blocking property of 54 is stereospecific the positive inotropic activity is not. Examples of 3- and 6-cyano and other closely related 1,4-dihydropyridine derivatives are described and evaluated for comparison and were found to be devoid of dual activities mentioned above.

Animals

Dopamine autoreceptor agonists as potential antipsychotics. 3.6-Propyl-4,5,5a,6,7,8-hexahydrothiazolo[4,5-f]quinolin-2-amine.

A series of rigid tricyclic analogues of the dopamine (DA) agonist PD 118440 [4-(1,2,5,6-tetrahydro-1-propyl-3-pyridinyl)-2-thiazolamine] was synthesized and evaluated for dopaminergic activity and DA autoreceptor selectivity. (R)-(+)-6-Propyl-4,5,5a,6,7,8-hexahydrothiazolo[4,5-f]quinolin+ ++-2-amine [+)-6) was identified as the most selective DA autoreceptor agonist from this group of compounds. It inhibited spontaneous locomotor activity (LMA) in rodents, reversed the gamma-butyrolactone (GBL) induced accumulation of rat striatal DOPA and inhibited brain DA neuronal firing, all suggestive of direct DA autoreceptor agonist activity. However, (+)-6 is not completely free of postsynaptic DA activity, as evidenced by its stimulation of LMA in rats at high doses and its ability to produce stereotypy. On the other hand, (-)-6 appears to be a weak partial DA agonist with some effects on brain DA synthesis only at high doses. Like other DA autoreceptor agonists and DA antagonists, (+)-6 inhibited Sidman conditioned avoidance in squirrel monkeys, a test predictive of clinical antipsychotic activity. However, unlike classical antipsychotics, (+)-6 did not induce dystonias in haloperidol-sensitized squirrel monkeys, suggesting a minimal propensity toward extrapyramidal side effects (EPS).

Animals

Loss of muscarinic M1 receptors with aging in the cerebral cortex of Fisher 344 rats.

Age-related changes in central cholinergic muscarinic receptors were measured in young (3-6 month), middle-aged (15-17 month), and aged (22-26 month) male Fisher 344 rats by receptor binding techniques. Using [3H]-quinuclidinyl benzilate as the ligand, a significant decrease (14-19%) in the number of muscarinic cortical receptors was measured in aged rats compared to both young and middle-aged rats. With the selective M1 antagonist, [3H]-pirenzepine, a 17% decrease in receptor density was observed in the cortex of aged animals compared to young rats. For both ligands no differences were observed in the striatum or hippocampus between any age group and there was no change in affinity (Kd) in any of the three brain regions for the three age groups. Additionally, there was no difference in choline acetyltransferase activity measured in cortex, hippocampus, or striatum of young and aged rats. Thus, there is a loss of M1 muscarinic receptors in the cerebral cortex of aged male Fisher 344 rats.

Aging

4-(1,2,5,6-Tetrahydro-1-alkyl-3-pyridinyl)-2-thiazolamines: a novel class of compounds with central dopamine agonist properties.

The design, synthesis, and pharmacological properties of a novel type of 4-(1,2,5,6-tetrahydro-1-alkyl-3-pyridinyl)-2-thiazolamine with dopaminergic properties are described. In particular, 4-(1,2,5,6-tetrahydro-1-propyl-3-pyridinyl)-2-thiazolamine (4c, PD 118440) and its allyl analogue (4i, PD 120697) have been identified as orally active dopamine (DA) agonists with pronounced central nervous system effects in tests that include [3H]-haloperidol and [3H]-N-propylnorapomorphine binding, inhibition of striatal DA synthesis, inhibition of DA neuronal firing, inhibition of spontaneous locomotor activity, and reversal of reserpine-induced depression in rats. The DA autoreceptor selectivity of these heterocyclic analogues of 3-(1-propyl-3-piperidinyl)phenol (3-PPP) was also evaluated. In this series, DA agonist activity was found to be highly dependent on the size of the N-alkyl substituent, the saturation level of the six-membered ring, and the mode of attachment of the 2-aminothiazole ring.

Animals

Synthesis and dopamine agonist properties of (+-)-trans-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano [4,3-b]-1,4-oxazin-9-ol and its enantiomers.

The dopamine agonist profile of (+-)-trans-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano [4,3-b]-1,4-oxazin-9-ol (16a) and its enantiomers (16b-c) was examined. Racemic 16a exhibited moderate affinity for the dopamine (DA) D2 receptor labeled with the DA antagonist ligand [3H]haloperidol and moderate in vivo activity; it attenuated gamma-butyrolactone-stimulated DA synthesis, decreased DA neuronal firing of substantia nigra DA neurons, and inhibited exploratory locomotor activity in rats, a profile consistent with a DA autoreceptor agonist mechanism of action. The (+)-enantiomer 16b possessed greater DA receptor affinity with the agonist ligand [3H]-N-propylnorapomorphine than with the antagonist ligand. In rats it potently inhibited DA synthesis and neuronal firing and also inhibited exploratory locomotion. The (-)-enantiomer, on the other hand, did not have significant activity in any of these tests. This profile indicates that like many other rigid DA agonists, the dopaminergic activity resides in one enantiomer, in this case the (+)-enantiomer 16b. On the basis of single-crystal X-ray analysis of a key intermediate, the absolute configuration of 16b was found to be 4aR, 10bR.

Animals

Structure-activity relationships for enhancement of adenosine A1 receptor binding by 2-amino-3-benzoylthiophenes.

The structural requirements for stimulation of adenosine A1 agonist binding by 2-amino-3-benzoylthiophenes and related compounds were investigated. Slowing of the dissociation of [3H]N6cyclohexyladenosine binding was used as a specific measure of the allosteric effects of these compounds. The thiophene ring could be replaced with benzene but not with several nitrogen-containing heterocycles. The 2-amino group was required, and at least one hydrogen on the amino group appeared to be necessary for activity. The keto carbonyl was also essential. Alkyl substitution at the 4-position of the thiophene ring increased activity, whereas 5-position substitution appeared to have little effect. Activity was also increased by various substitutions on the phenyl ring, with 3-(trifluoromethyl) showing optimal activity. The phenyl ring could be replaced with cyclohexyl without major loss of activity. 1-Aminofluoren-9-one, a conformationally locked derivative, was active. Based in part in the latter observation, the active conformation is proposed to have an intramolecular hydrogen bond between the amino nitrogen and the carbonyl oxygen. Because the 2-amino-3-benzoylthiophenes showed competitive adenosine antagonism as well as allosteric enhancement, their affinities as competitive inhibitors of [3H]8-cyclopentyl-1,3-dipropylxanthine binding to A1 receptors were also assessed. Structure-activity relationships for competitive antagonism were distinct from those for allosteric enhancement, with ratios between the two activities varying by more than 1000-fold. Of the analogs tested, (2-amino-4,5-dimethyl-3-thienyl)-[3-(trifluoromethyl)phenyl]methanone (PD 81,723) had the most favorable ratio of enhancement to antagonism.

Adenosine

Effects of CI-926 (3-[4-[4-(3-methylphenyl)-1-piperazinyl] butyl]-2,-4-imidazolidinedione), an antihypertensive agent, on rat brain catecholamine and serotonin turnover.

The effects of the antihypertensive drug CI-926 on rat brain norepinephrine (NE), dopamine (DA), and serotonin (5-HT) turnover and its in vitro affinity for several receptors were investigated. CI-926 (3-30 mg/kg intraperitoneally, i.p.) caused a dose-dependent increase in the rate of brain stem NE synthesis and increased the decline in NE after inhibition of its synthesis by alpha-methyl-p-tyrosine. These findings indicated that CI-926 increased brain NE turnover, probably as a compensatory response to central adrenoceptor blockade based on its nanomolar affinity for alpha 1-adrenoceptors and micromolar affinity for alpha 2-adrenoceptors. CI-926 also increased the rate of DA synthesis and DA metabolite levels; this indicates an increase in DA turnover. The latter effect of CI-926 is attributed to a compensatory response to DA-2 receptor blockade because no affinity for DA-1 relative to DA-2 receptors was found and the effect was antagonized by the DA agonist pergolide. CI-926 decreased brain 5-HT turnover, as indicated by reduced concentrations of the 5-HT metabolite 5-hydroxyindoleacetic acid and a reduced rate of 5-HT synthesis, effects characteristic of centrally acting 5-HT agonists. Based on its affinity for 5-HT-1A receptors versus 5-HT-1B and 5-HT-2, the decrease in 5-HT synthesis and release is interpreted as evidence of 5-HT-1A receptor activation. These findings indicate that besides peripheral alpha 1-adrenergic blockade, an interference of CI-926 with central adrenergic and serotoninergic neurotransmission may contribute in part to an explanation of its antihypertensive properties.

Animals

PD 122860: a novel dihydropyridine with sodium channel stimulating and calcium channel blocking properties.

The cardiac and vascular activities of ethyl 5-cyano-1,4-dihydro-6-methyl-2-[(4-pyridinyl-sulfonyl)methyl]-4-[2- (trifluoromethyl)phenyl]-3-pyridine carboxylase (PD 122860), a novel dihydropyridine, were investigated in vitro using rat heart and rabbit aorta, and compared with reference inotropic and vasodilator agents. In the rat heart, PD 122860 increased left ventricular contractility, decreased coronary resistance and altered the shape of the electrocardiogram T-wave. All three effects were observed at comparable concentrations of PD 122860. The inotropic response to PD 122860 was reversed by the Na+ channel blocker tetrodotoxin and blunted by the Na+-Ca++ exchange inhibitor dichlorobenzamil. The effects of tetrodotoxin and dichlorobenzamil on the inotropic response to the reference Na+ channel stimulant veratridine were comparable to PD 122860, whereas tetrodotoxin and dichlorobenzamil had no inhibitory effect on the inotropic responses to the adenylate cyclase stimulator forskolin or the Ca++ channel stimulant BAY K 8644. PD 122860 selectively relaxed potassium-contracted aortic rings and inhibited [3H]nitrendipine binding to rat brain membranes, suggesting that the vasodilator activity of PD 122860 is due to Ca++ channel blockade. In contrast to BAY K 8644, PD 122860 did not contract partially depolarized aortic rings, suggesting an absence of Ca++ channel stimulant activity. PD 122860 is a racemic mixture and both the vasorelaxant and [3H]nitrendipine binding inhibitory activities selectively reside in the (+)-enantiomer [(+)-PD 122860]. In contrast, the inotropic response resides with both enantiomers of PD 122860. It is therefore concluded that PD 122860 represents a unique dihydropyridine derivative which possesses both Na+ channel stimulating and Ca++ channel blocking activities.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy

CI-943, a potential antipsychotic agent. II. Neurochemical effects.

The effects of CI-943 (a novel 8-ethyl-7,8-dihydro-1,3,5-trimethyl-1H-imidazo[1,2-c]pyrazolo[3,4- e]pyrimidine compound exhibiting a favorable antipsychotic profile in animal tests) on neurochemical parameters related to biogenic amine neurons have been studied in rat brain. CI-943 (1-40 mg/kg p.o. and 20 mg/kg i.p.) accelerated the turnover of dopamine (DA) in rat brain as demonstrated by the enhancement of levels of the DA metabolites homovanillic acid, 3,4-dihydroxyphenylacetic acid or 3-methoxytyramine and by the enhancement rate of DA synthesis in either striatum or mesolimbic regions. These increases in DA turnover induced by CI-943 are not due to DA receptor blockade as CI-943, unlike known antipsychotics, did not exhibit affinity for DA receptors either in vitro or in vivo and did not affect rat serum basal prolactin levels. Amfonelic acid enhanced the action of haloperidol in increasing striatal homovanillic acid with no effect on that of CI-943 and clozapine, suggesting that CI-943, like clozapine, would be predicted to have a low risk of extrapyramidal side effects as compared to haloperidol. Chronic administration of CI-943 (40 mg/kg i.p.) to rats for 28 days did not affect the affinity or number of striatal DA receptors; in comparison haloperidol (0.5 mg/kg i.p.) caused an increase in number of DA receptors with no change in affinity. Measures of serotonergic function were increased; noradrenergic function was not affected by CI-943, nor did it exhibit affinity for a number of central nervous system receptors in vitro. The molecular mechanism by which CI-943 increases brain DA turnover is not known at this time but appears to be unique in comparison to known antipsychotic agents.

Animals

Interaction between propranolol and calcium channel blockers in cardiac and vascular smooth muscle.

The ability of the beta-receptor antagonist propranolol to influence the response of isolated cardiac and vascular smooth muscle to several classes of calcium channel blockers was examined. For comparison, the interactions between propranolol and other classes of negative inotropic and vasorelaxant agents was also evaluated. The results of these studies demonstrate that propranolol pre-treatment significantly enhances the in vitro response to the dihydropyridine calcium channel blocker nifedipine, but not the thiazapine calcium channel blocker diltiazem. This enhancement was unrelated to the negative inotropic or vasorelaxant properties of these agents. In addition, propranolol pre-treatment of rat cortical membranes also enhanced the affinity of nifedipine for the 3H-nitrendipine binding site, but did not alter the effect of diltiazem on 3H-nitrendipine binding. These observations suggest that a direct interaction may exist between beta-receptor antagonists and dihydropyrine-type calcium channel blockers. This interaction may be an important factor in selecting drug therapy for conditions such as hypertension and angina.

Animals

Synthesis and potential antipsychotic activity of 1H-imidazo[1,2-c]pyrazolo[3,4-e]pyrimidines.

The synthesis of a series of 1H-imidazo[1,2-c]pyrazolo[3,4-e]pyrimidines is reported along with the effects of these compounds in preclinical tests for antipsychotic activity. Certain of these compounds displayed antipsychotic-like effects in conditioned avoidance tests, but unlike currently used antipsychotic drugs, they did not have affinity for brain dopamine receptors. These compounds also did not cause dystonias predictive of extrapyramidal side effects in monkeys at doses that produced behavioral effects. On the basis of this unique biological profile, a member of this series 7,8-dihydro-8-ethyl-1,3,5-trimethyl-1H-imidao[1,2-c]pyrazol[3,4-e] pyrimidine (19, CI-943), has been selected for clinical evaluation as an antipsychotic agent.

Animals

6- and 8-hydroxy-3,4-dihydro-3-(dipropylamino)-2H-1-benzopyrans. Dopamine agonists with autoreceptor selectivity.

The dopamine agonist profiles of 3,4-dihydro-3-(3-dipropylamino)-2H-1-benzopyran-6- and -8-ol (4 and 5, respectively) were examined. Both 4 and 5 exhibited greater relative affinity for receptors labeled with the dopamine agonist ligand [3H]propylnorapomorphine than for those labeled with the dopamine antagonist ligand [3H]haloperidol. Both compounds attenuated the stimulation of brain dopamine synthesis caused by gamma-butyrolactone (GBL) and decreased the firing rate of substantia nigra dopamine neurons in rats. This profile of activity, together with the ability of the dopamine antagonist haloperidol to reverse the inhibition of dopamine neuronal firing, indicate that both compounds are brain dopamine agonists.

4-Butyrolactone

Dopamine autoreceptor agonists as potential antipsychotics. 1. (Aminoalkoxy)anilines.

The synthesis and pharmacological properties of a novel type of [(arylpiperazinyl)alkoxy]anilines with dopaminergic properties are described. One of these compounds, 3-[3-(4-phenyl-1-piperazinyl)propoxy]benzenamine (4c), has been identified as a selective dopamine (DA) autoreceptor agonist in tests that include [3H]haloperidol binding, inhibition of striatal DA synthesis, inhibition of DA neuronal firing, inhibition of spontaneous locomotor activity, and reversal of reserpine-induced depression in rats. In addition, 4c possesses good oral activity in the Sidman conditioned avoidance test in squirrel monkeys, which is indicative of antipsychotic activity. In a primate model, 4c was found to lack the liability for extrapyramidal side effects usually associated with antipsychotic drugs.

Aniline Compounds

2-(2-Aryl-2-oxoethylidene)-1,2,3,4-tetrahydropyridines. Novel isomers of 1,4-dihydropyridine calcium channel blockers.

The title compounds are novel double bond isomers of 1,4-dihydropyridine-type calcium channel blockers (CCB). These derivatives were prepared by using the Hantzsch dihydropyridine synthesis. The assignment of structure was based on spectroscopic data and a regiochemically unambiguous synthesis. Several of the analogues inhibited [3H]nitrendipine binding with IC50 values as low as 25 nM. By comparison, nifedipine, a clinically useful 1,4-dihydropyridine CCB, inhibits [3H]nitrendipine binding with an IC50 of 1.6 nM. In the Langendorff rat heart preparation, treatment with the more potent derivatives produced marked dose-related increases in coronary flow with little or no effect on heart rate or contractility, except at the highest concentrations tested. The selectivity for vascular versus cardiac effects was similar to that of nifedipine, i.e., the concentration producing vasodilation was approximately 2 orders of magnitude lower than the concentration eliciting cardiodepression. These novel isomers extend the structure-activity relationships for calcium channel blockers into a series closely related to the 1,4-dihydropyridines.

Animals

1,3-Dialkyl-4-(iminoarylmethyl)-1H-pyrazol-5-ols. A series of novel potential antipsychotic agents.

2-(Diethylamino)-N-[4-(2-fluorobenzoyl)-1,3-dimethyl-1H-pyrazol-5-yl] acetamide (1) was recently found to have an antipsychotic-like profile in behavioral animal tests but, unlike clinically available antipsychotic agents, did not interact with dopamine receptors. Compound 1 was apparently metabolized to (5-amino-1,3-dimethyl-1H-pyrazol-4-yl)(2-fluorophenyl)methanone (2), which was both active in the behavioral animal tests and toxic. The synthesis and pharmacological evaluation of a series of 1,3-dialkyl-4-(iminoarylmethyl)-1H-pyrazol-5-ols are described in which the hydroxy and imine functionalities were selected as possible isosteric replacements for the amino and ketone groups of the earlier series. The initial target, 1,3-dimethyl-4-(iminophenylmethyl)-1H-pyrazol-5-ol (28), like known antipsychotics, reduced spontaneous locomotion in mice at doses that did not cause ataxia, and unlike known agents, it did not bind to D2 dopamine receptors in vitro. An examination of the SAR of related compounds indicated that maximal activity was obtained with analogues containing methyl groups at the 1- and 3-positions on the pyrazole ring and with a 3-chloro substituent on the phenyl ring. Replacement of the hydrogen atom of the imine moiety with various substituents led to loss of activity. Attempts to synthesize the 2-fluorophenyl compound analogous to 2 resulted in ring-closure to 1,3-dimethyl[1]benzopyrano[2,3-c]pyrazol-4-(1H)-one (65). 4-[(3-Chlorophenyl)iminomethyl]-1,3-dimethyl-1H-pyrazol-5-ol (41) was evaluated in additional tests. It inhibited conditioned avoidance responding in both rats and monkeys but, unlike available antipsychotic drugs, did not elicit dystonic movements in a primate model of antipsychotic-induced extrapyramidal side effects.

Animals