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Y Clement-Cormier

Publications and source records attributed to Y Clement-Cormier.

9 recordsLinked to original sources
PubMed1983

Evidence for a cyclic GMP mechanism in the mediation of hippocampal post-tetanic potentiation.

Correlative electrophysiological and biochemical techniques were used to study hippocampal post-tetanic potentiation in acutely prepared rabbits following stimulation of the medial septal region and contralateral hippocampal field CA3. The results indicate that calcium ions, guanosine-3':5'-monophosphate, and phosphodiesterase inhibitors selectively enhanced the duration of post-tetanic potentiation. Potassium ions selectively enhanced tetanic potentiation. Adenosine-3':5'-cyclic monophosphate suppressed both tetanic and post-tetanic potentiation. The electrophysiological findings were supported by biochemical observations that guanosine-3':5'-monophosphate levels show marked increases following tetanic stimulation of either the medial septal region or contralateral hippocampal field CA3 pathways. The data suggest that a calcium-dependent process in the presence of a guanosine-3':5'-monophosphate mechanism promotes periods of hippocampal pyramidal cell hyperexcitability. The mechanism by which the cyclic nucleotide alters potentiation does not appear to be coupled to a single receptor variety.

Animals↗
PubMed1981

Detection of dopamine receptors in the area postrema.

[3H]Spiroperidol labeled dog area postrema membranes with high affinity (KD, 0.1 nM) and stereospecificity. The displacement of the radioligand by different dopamine agonists and antagonists indicated that the labeled sites were dopaminergic in nature. Guanine nucleotides decreased agonist affinity for the labeled sites without affecting the affinity for antagonists. Adenylate cyclase in the area postrema was stimulated by guanine nucleotides and sodium fluoride but not by dopamine. The results suggest that the dopamine receptor in the area postrema can be classified as D2-type receptors.

Adenylyl Cyclases↗
PubMed1980

Identification and partial purification of a hydrophobic protein component associated with [3H]spiroperidol-binding activity.

The binding activity of radiolabelled neuroleptic drugs has been used to biochemically and pharmacologically characterize the dopamine receptor in brain. An extract which binds [3H]spiroperidol and exhibits stereoselectivity for (+)- and (-)-butaclamol, has been isolated from the calf striatal microsomal fraction. Specific binding activity in the chloroform-methanol extract of this preparation is enhanced over that of the crude homogenate. The highest specific binding of the chloroform methanol extract is associated with the crude phospholipid component which is enriched in hydrophobic proteins and acidic phospholipids. Subfractionation of the crude phospholipid extract by gel filtration (Sephadex LH-20) yields multiple peaks of [3H]spiroperidol binding activity, however four major zones of specific binding activity were detected. These results demonstrating a close association of phospholipids with a dopamine binding site suggest a functional role for proteolipid in receptor recognition and regulation.

Animals↗
PubMed1980

Inhibition of cyclic nucleotide accumulation following hippocampal tetanic potentiation: effects of diazepam.

Biochemical studies on the hippocampus of acutely prepared rabbits revealed more than twofold increases in cyclic GMP levels following tetanic potentiation of the pathway from the medial septal region to CA1 pyramidal cells. Diazepam, administered intravenously, prevented the elevation in cyclic GMP levels in this region and also attenuated the post-tetanic potentiation seen following the presentation of trains at frequencies within theta rhythm. The results imply a modulatory role for cyclic nucleotides in the enhancement of pyramidal cell excitability and suggest that the biochemical mechanism for the psychoactive benzodiazepines may well include the suppression of cyclic GMP levels.

Animals↗
PubMed1980

[3H]2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalen (ADTN). Regional distribution and in vivo binding after acute and chronic drug treatment.

The regional distribution and in vivo binding of the dopamine analog 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalen (ADTN) was studied in the brain. The highest density of binding sites was in the striatum, with virtually no binding in the cerebellum. The binding of [3H]ADTN reflects an occupation of specific dopamine sites because the binding was diminished by the simultaneous administration of the dopamine antagonist haloperidol or the dopamine precursor L-3,4-dihydroxyphenylalanine (L-dopa). Chronic administration of haloperidol or L-dopa prior to assaying for in vivo binding resulted in an increase in the number of sites for [3H]ADTN which correlates to the increase observed in in vitro assays following long-term treatment with these agents. The subcellular distribution of in vivo labeled ADTN sites in the caudate nucleus indicate a high density of specific binding sites in the microsomal fraction, P3. Overall, these data demonstrate that the aminotetralins, such as ADTN, which bind with high affinity to the dopamine receptor in the caudate nucleus in vitro and in vivo, can provide precise information on the topography of this receptor.

Animals↗
PubMed1978

[3H] 2-Amino-6,7-dihydroxy 1,2,3,4-tetrahydronapthalene (ADTN): a potential specific dopamine receptor ligand.

The characteristics of [3H] 2-amino-6,7-dihydroxy 1,2,3,4-tetrahydronapthalene (ADTN) binding to calf striatal membranes were investigated. [3H]ADTN was observed to bind with high affinity and stereospecificity to a preparation of crude synaptic membranes. A number of dopamine agonists and antagonists were studied for their ability to displace bound [3H]ADTN. Dopamine agonists were found to be more potent inhibitors of ADTN binding than were dopamine antagonists. Kinetic analysis indicates that [3H]ADTN binds to dopamine recognition sites in a manner comparable to dopamine itself. Overall, the data suggest that ADTN may be a useful ligand for the characterization of agonist requirements for recognition by dopamine binding sites.

Animals↗