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Biomedical subjects

M Titeler

Publications and source records attributed to M Titeler.

66 records · Page 4Linked to original sources
PubMed1978

Antiparkinsonian drug doses and neuroleptic receptors.

The clinical potency of 3 drugs, apomorphine, N-propylnorapomorphine, and bromocryptine, have been found to be closely correlated to their potencies in competing for 3H-haloperidol and 3H-spiroperidol both of which label the dopamine receptor. This correlation indicates that the direct binding assay may be used to predict clinical potencies of anti-parkinsonian drugs, and indicates that agonists as well as antagonists compete potently for 3H-neuroleptic binding.

Animals↗
PubMed1978

Multiple receptors for brain dopamine.

This study was done to obtain direct in vitro evidence for the possible existence of more than one type of dopaminergic binding site in homogenates of the caudate nucleus from calf brain. Five radioligands for dopaminergic sites were tested. The inhibitions of two agonist radioligands ([3H]dopamine, [3H]apomorphine) by haloperidol, chlorpromazine, or piflutixol were biphasic. The inhibitions of [3H]haloperidol, [3H]spiroperidol, and [3H]dihydroergocryptine binding by dopamine and (-)-norepinephrine were also biphasic. Thus, both 3H-labeled agonists and 3H-labeled antagonists were possibly binding to two high-affinity sites.

Animals↗
PubMed1978

Selective labeling of alpha-adrenergic receptors in caudate nucleus by [3H] dihydroergocryptine in the presence of spiperone-blocked dopamine receptors.

Because it was known that [(3)H]dihydroergocryptine can label alpha-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 alpha-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 alpha receptors. The alpha-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 alpha receptors. These results with [(3)H]dihydroergocryptine as an alpha-adrenergic receptor ligand correlate well with those published by others for [(3)H]WB-4101.

Adrenergic alpha-Antagonists↗