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P Seeman

Publications and source records attributed to P Seeman.

At least 199 records · Page 11Linked to original sources
PubMed1982

Comparison of soluble dopamine D2-receptors from three species.

In order to determine the species which would provide the highest yield of soluble and specific D2-type dopamine receptors, the striata from human, calf and canine brains were solubilized by 1% digitonin. The receptors were detected with [3H]spiperone, using Sephadex G-50 columns or polyethylene glycol precipitation. The soluble D2-sites from the human and canine tissue had about the same KD and rank order of drug affinities as the native membrane preparations. The binding characteristics of the calf D2-receptors were considerably altered, however, upon solubilization; the affinities for spiperone and chloropromazine were reduced 12-fold, and the non-specific binding increased from 28 to 50%. Calf caudate is a poor choice for dopamine receptor solubilization using digitonin. The solubilized canine tissue, however, provided an excellent source of D2-receptors because of its similarity to soluble human D2-receptors and its stability in solution.

Animals↗
PubMed1982

Reversible drug-induced parkinsonism. Clinicopathologic study of two cases.

Parkinsonism developed in two patients who were received neuroleptic drugs. In each case the clinical manifestations remitted completely when the offending drug or drugs were discontinued. Histologic examination in each patient disclosed abnormalities characteristic of idiopathic paralysis agitans (IPA). Levels of homovanillic acid were low in both cases, and dopamine (DA) levels were measurably reduced in the striatum in one case. It is postulated that before administration of neuroleptic drugs, both patients had preclinical IPA, which predisposed them to parkinsonism when challenged with DA antagonists. Our observations suggest that some patients with irreversible drug-induced parkinsonism may suffer from IPA and that the reversibility of clinical features does not exclude the presence of subclinical IPA.

Aged↗
PubMed1982

Amphetamine-induced hypolocomotion in mice with more brain D2 dopamine receptors.

The relationship between brain D2 dopamine receptors and locomotor response to amphetamine was investigated in eight strains of mice. The D2 receptor is defined as that dopaminergic site with high affinity (nanomolar) for neuroleptics and low affinity (micromolar) for agonists. D2 receptors were measured in the striatum and olfactory tubercle using [3H]spiperone and 10 microM sulpiride to define specific binding. Four inbred strains of mice (CBA/J; C57BL/6J; DBA/2J; SEC/1ReJ) had low receptor densities of about 380 and 160 fmoles/mg protein in the striatum and olfactory tubercle, respectively; all these mice were essentially nonresponsive (i.e., locomotion) to low doses of amphetamine (0.5 and 1.0 mg/kg i.p.) or showed hyperlocomotion to high doses (5 mg/kg). Three other mouse strains (BALB/cJ; A/J; C3H/HeJ) had higher densities of about 600 and 230 fmoles/mg protein in the striatum and olfactory tubercle, respectively, and these mice all responded with hypolocomotion to the low doses and hyperlocomotion to the high dose of amphetamine. The two genetically different populations, one of which responded to amphetamine with hypolocomotion while the other did not, are analogous to hyperactive children, only 70% of whom respond to amphetamine-like drugs. Thus, the mice with high receptor density may serve as a model for studying the hyperactivity syndrome which may be associated with dopaminergic dysfunction.

Animals↗
PubMed1982

[3H]dopamine labeling of D3 dopaminergic sites in human, rat, and calf brain.

The binding of [3H]dopamine to brain regions of calf, rat, and human was investigated. The calf caudate contained the highest density of [3H]dopamine binding sites, with a Bmax value of 185 fmol/mg protein, whereas rat and human striatum contained one-third this number of sites. The KD values for [3H]dopamine in all tissues were 2-3 nM. Dopaminergic catecholamines (dopamine, apomorphine, 6,7-dihydroxy-2-aminotetralin, and N-propylnorapomorphine) inhibited the binding of [3H]dopamine in all three species, at low concentrations, with IC50 values of 1.5 to 6 nM. Neuroleptics, in contrast, inhibited the binding at high concentrations (with IC50 values of 200 to 40,000 nM). The [3H]dopamine binding sites were saturable, heat-labile, and detectable only in dopamine-rich brain regions; these sites differed from D2 dopamine sites (labeled by [3H]butyrophenone neuroleptics), and from D1 dopamine sites (labeled by [3H]thioxanthene neuroleptics) associated with the dopamine-stimulated adenylate cyclase. We have, therefore, called these high-affinity [3H]dopamine binding sites D3 sites. [3H]Apomorphine and [3H]ADTN also appeared to label D3 sites. These ligands however, were less selective than [3H]dopamine, and labeled sites other than D3 as well. Assay conditions were important in determining the parameters of [3H]dopamine binding. The optimum conditions for selective labeling of the D3 dopaminergic sites, using [3H]dopamine, required the presence of EDTA and ascorbate.

Animals↗
PubMed1982

Effects of antihypertensive clonidine congeners on alpha-adrenergic receptors.

Evidence in the literature suggests that the antihypertensive effects of clonidine stem from its action on alpha-2 adrenergic receptors. In order to examine this possibility we tested the effects of 13 congeners of clonidine on the binding of [3H]WB-4101 and [3H]clonidine to calf frontal cortex homogenates; [3H]WB-4101 served as a label for alpha-1 receptors while [3H]clonidine served to label alpha-2 adrenergic receptors. All the substituted imidazolines were two to three orders more potent in inhibiting the binding of [3H]clonidine than they were against [3H]WB-4101. There was a strong correlation between the antihypertensive doses of these congeners and their concentrations required to inhibit the binding of [3H]clonidine. The results are compatible with the concept that the antihypertensive action of clonidine is more likely due to interactions with alpha-2 adrenergic receptors than with alpha-1 receptors.

Animals↗
PubMed1982

Striatal binding of 2-amino-6,7-[3H]dihydroxy-1,2,3,4-tetrahydronaphthalene to two dopaminergic sites distinguished by their low and high affinity for neuroleptics.

In order to develop more selective methods for labeling brain dopamine receptors, this study describes in detail the properties of 2-amino-6,7,-[3H]dihydroxy-1,2,3,4,-tetrahydronaphthalene ([3H] ADTN) binding to dopaminergic sites in rat, calf, and human brain. [3H]ADTN labeled two distinct types of dopaminergic binding sites in the brain striatum of the rat, calf, and human. Very low concentrations of dopamine and dopaminergic catecholamines (with IC50 values of 1 to 10 nM) inhibited the binding of [3H]ADTN to both sites. Neuroleptics, however, inhibited the binding of [3H]ADTN in two distinctly separate concentration ranges, with IC50 values of 0.15 to 40 nM at one site and 100 and 50,000 nM at the other site. The site with high affinity for dopamine and low affinity for neuroleptics had binding properties that corresponded to those of the previously characterized D3 site (List, S., M. Titeler, and P. Seeman (1980) Biochem. Pharmacol. 29: 1621-1622). The [3H]ADTN binding site with high affinity for neuroleptics demonstrated binding characteristics similar to a site labeled by 3H-Neuroleptics (Sokoloff, P., M. P. Martres, and J. C. Schwartz (1980) Naunyn Schmiedebergs Arch. Pharmacol. 315: 89-102). [3H]Apomorphine appeared to label the same two sites as [3H]ADTN, while [3H]dopamine labeled only the D3 site. Scatchard analysis of [3H]ADTN or [3H]apomorphine binding, under conditions for selective labeling of the low affinity neuroleptic site (D3) and the high affinity site for neuroleptics, detected a density of 70 fmol/mg of protein for each. The density of the D3 site in the calf striatum (170 fmol/mg of protein) was much greater than that of the high affinity neuroleptic site (50 fmol/mg). In the rat, the dissociation constant (KD) of [3H]ADTN was 2 nM for both sites. [3H]Apomorphine, however, had a higher affinity for the D3 site (KD=1.6 nM) than for the high affinity neuroleptic site (KD=4.2 nM). The present results may explain previously observed species and laboratory differences between the binding of [3H]ADTN, [3H]apomorphine, and [3H]dopamine.

Animals↗
PubMed1981

Assay for soluble dopamine receptors by the precipitation method.

Receptors with high affinity for neuroleptics (D2-type dopamine receptors) were solubilized from dog striatum using 1% digitonin. Soluble receptors were labelled using [3H]spiperone, and the bound 3H-ligand was separated from the free [3H]spiperone by molecular sieving on the Sephadex G-50 columns. This paper presents a polyethylene glycol (PEG) precipitation method designed to replace this column method. IC50 values for both neuroleptics and dopamine agonists, as well as dissociation constants for [3H]spiperone were similar for both methods. The precipitation method yielded a receptor density of 64 fmol/mg protein whereas the molecular sieving technique yielded a value of 194 fmol/mg protein. The qualitative similarities between the methods validates using the rapid precipitation method for monitoring the receptor during various stages of its purification.

Animals↗
PubMed1981

D2- but not D3-dopamine receptors detected in the anterior pituitary.

Using conditions which revealed high affinity binding sites for [3H]ADTN (KD of 1.6 nM), [3H]apomorphine (DK of 3.5 nM) and [3H]dopamine (KD of 1,5 nM) in the calf caudate nucleus, no such high affinity sites could be detected in the calf anterior pituitary gland. In contrast, high affinity binding sites for [3H]-spiperone were found in both the caudate and the anterior pituitary. The apparent absence of high affinity sites for these [3H]-catecholamine ligands (in the 1-10 nM region) and the presence of the [3H]spiperone binding site in the anterior pituitary is compatible with the view that the pituitary [3H]neuroleptic receptor with its low affinity for dopamine, may be the physiological site of dopamine action in the pituitary. THe data, therefore, support the presence of D2- but not D3-dopamine receptor sites in the calf anterior pituitary.

Animals↗
PubMed1981

Solubilization of neuroleptic/dopamine receptors of human brain striatum.

Dopaminergic neuroleptic receptors were solubilized by digitonin from post-mortem human brain putamen. The receptors were labelled by [3H]spiperone and separated from free [3H]spiperone by sephadex chromatography. Neuroleptics and neurotransmitters had similar inhibitory and stereoselective potencies on the solubilized and intact membrane receptors. The KD for [3H]spiperone was apparently high for the solubilized receptors. Unlike the rat striatum, therefore, the human putamen can be solubilized to release neuroleptic/dopamine receptors, permitting the future development of highly sensitive methods for detecting dopamine receptors.

Antipsychotic Agents↗
PubMed1981

Relation between brain catecholamine receptors and dopaminergic stereotypy in rat strains.

In order to examine the potential relation between behaviour elicited by apomorphine and the density of catecholamine receptors, we studied stereotypy and the binding of [3H]spiperone to D2-(or neuroleptic/dopamine) receptors, of [3H]WB-4101 to alpha1-adrenoceptors, and [3H]clonidine to alpha2-adrenoceptors in two strains of rats. The F344 rats exhibited significantly more stereotypy to apomorphine than the Buffalo strain of rats. Other F344 rats which did not receive apomorphine and 34% more D2-receptors in the striatum and 50% more D2-receptors in the olfactory tubercle. Alpha2-Receptors in the frontal cortex were 20% higher in F344 rats when compared to the Buffalo strain, while alpha 1-receptors were the same across both strains. These results suggest a relation between D2-dopamine/neuroleptic receptor density and behavioural responsiveness to the direct-acting and specific dopamine agonist, apomorphine.

Analysis of Variance↗
PubMed1981

Differential effect of chronic desipramine and amitriptyline treatment on rat brain adrenergic and serotonergic receptors.

Serotonergic and adrenergic receptors were examine in rat brains by direct binding assays after chronic treatment with tricyclic antidepressants. Chronic amitriptyline (AMT) treatment (10 mg/kg/day i.p. for 21 days) decreased specific 3H-spiperone binding in the cortex and not in the caudate nuclei. Specific 3H-dihydroalprenolol (3H-DHA) binding was reduced in cerebellar but not in cerebral cortex. Chronic desipramine (DMI) treatment given in the same dose schedule, on the other hand, decreased specific 3H-DHA binding in both cerebellar and cerebral cortex. Specific 3H-spiperone binding in the cerebral cortex was also reduced but to a lesser extent than that in the AMT treated group. Scatchard analysis showed that reductions in 3H-spiperone or 3H-DHA binding in all cases were due to decreases in number of binding sites (Bmax) and not to changes in dissociation constants (KD). No change was observed in 3H-serotonin (3H-5HT), 3H-clonidine, or 3H-WB-4101 binding. The results show that there is no single common change in brain adrenergic and serotonergic receptors after chronic AMT and DMI treatment.

Amitriptyline↗
PubMed1981

Resolution of dopamine and serotonin receptor components of [3H]spiperone binding to rat brain regions.

A procedure was developed to identify receptors for dopamine and serotonin separately and selectively by means of [3H]spiperone and to measure the density of each receptor in different regions of the rat brain. In the striatum, the binding of [3H]spiperone to dopamine receptors was inhibited by sulpiride but not by quinazolinedone R43448 (R43448); in the frontal cortex, however, the binding of [3H]spiperone to serotonin receptors was inhibited by R43448 but not by sulpiride. Thus, the density of dopamine receptors (D2 sites) was measured by [3H]spiperone binding in the presence of 0.1 microM R43448 (to preclude the attachment of the 3H-labeled ligand to serotonin sites), while the density of serotonin receptors (S2 sites) was measured by [3H]spiperone binding in the presence of 10 microM sulpiride (to preclude the attachment of the 3H-labeled ligand to dopamine sites). The density of D2 sites was highest in the striatum, followed by the olfactory tubercle, hypothalamus, substantia nigra, and the lower pons--medulla region. All five regions had similar dissociation constants (Kd values) of 0.05--0.15 nM. The density of S2 sites was highest in the frontal cortex, followed by the posterior cortex, olfactory tubercle, striatum, hypothalamus, and thalamus, and all regions had Kd values in the range 0.6--2.3 nM. Thus, because the Kd values were similar for all regions, and because Scatchard analyses revealed a single set of sites for either D2 or S2 (where detected), the main criteria for resolving the dopamine and serotonin components of [3H]spiperone binding were considered fulfilled.

Animals↗
PubMed1981

Multiple binding sites for [3H]clonidine and [3H]WB-4101 in rat brain.

Binding of the alpha-adrenergic agonist [3H]clonidine and the alpha-adrenergic antagonist [3H]WB-4101 exhibited multiple binding site characteristics in both rat frontal cortex and cerebellum. Kinetic analysis of the dissociation of both radioligands in rat frontal cortex suggests two high affinity sites for each ligand. Competition of various noradrenergic agonists and antagonists for [3H]WB-4101 binding yielded shallow competition curves, with Hill coefficients ranging from 0.45 to 0.7. This further suggests multiplicity in [3H]WB-4101 binding. In the rat cerebellum, competition of various noradrenergic drugs for [3H]clonidine binding yielded biphasic competition curves. Furthermore Scatchard analysis of [3H]clonidine binding in rat cerebellum showed two high affinity sites with KD = 0.5 nM and 1.9 nM, respectively. Competition of various noradrenergic drugs for [3H]WB-4101 binding in the rat cerebellum yielded biphasic competition curves. Lesioning of the dorsal bundle with 6-hydroxydopamine did not significantly affect the binding of either [3H]clonidine or [3H]WB-4101. These findings for both [3H]clonidine and [3H]WB-4101 binding in rat frontal cortex and cerebellum can be explained by the existence of postsynaptic binding sites for both 3H ligands.

Adrenergic alpha-Agonists↗