Selective labeling of α-adrenergic receptors in caudate nucleus by [3H]dihydroergocryptine in the presence of spiperone-blocked dopamine receptors
| Autor: | P. Seeman, M. Titeler |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 1978 |
| Předmět: |
medicine.medical_specialty
Spiperone Adrenergic receptor Dihydroergotoxine Pharmacology Binding Competitive Receptors Dopamine Radioligand Assay Dopamine Internal medicine medicine Animals Chlorpromazine Receptor Adrenergic alpha-Antagonists Neurotransmitter Agents Multidisciplinary Chemistry Receptors Adrenergic alpha Ligand (biochemistry) Receptors Adrenergic Endocrinology Tranquilizing Agents Dopamine receptor Cattle Biological Sciences: Biochemistry Caudate Nucleus Dihydroergocryptine medicine.drug |
| Popis: | Because it was known that [ 3 H]dihydroergocryptine can label α-adrenergic receptors as well as dopamine receptors, this study was done to establish the conditions under which [ 3 H]dihydroergocryptine would be a reliable ligand for selective labeling of α-adrenergic receptors. The calf caudate was chosen because it contains both dopamine and adrenergic receptors, and 5 nM spiperone (spiroperidol) was used to block the neuroleptic/dopamine receptors. Thus, in the presence of spiperone, [ 3 H]dihydroergocryptine exhibited saturable binding with a K d of 0.73 nM and a total number of sites of 150 fmol/mg of protein. The catechol neurotransmitters competed for [ 3 H]dihydroergocryptine binding in the potencies order epinephrine > (-)-norepinephrine > dopamine, indicating that [ 3 H]dihydroergocryptine (in the presence of 5 nM spiperone) was revealing α receptors. The α-adrenergic antagonists also competed for binding in the appropriate order: phentolamine > phenoxybenzamine > dibenamine. Finally, chlorpromazine was more potent than haloperidol in competing for [ 3 H]dihydroergocryptine, also in accord with the properties of α receptors. These results with [ 3 H]dihydroergocryptine as an α-adrenergic receptor ligand correlate well with those published by others for [ 3 H]WB-4101. |
| Databáze: | OpenAIRE |
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