Presynaptic alpha 2A/D-autoreceptors in the brain cortex of Cercopithecus aethiops.
The existence of presynaptic alpha 2-autoreceptors, and the subtype to which the receptors belong, were studied in the brain cortex from two African green monkeys (Cercopithecus aethiops). Slices of the brain cortex were preincubated with 3H-noradrenaline. The slices were then superfused with medium containing desipramine (1 microM) and stimulated electrically with trains of 72 pulses. 3 Hz. Concentration-response curves of nine alpha-adrenoceptor antagonists were determined. All antagonists enhanced the stimulation-evoked overflow of tritium, i.e. the release of noradrenaline, indicating the existence of presynaptic alpha 2-autoreceptors. The EC30%, values of the antagonists (concentrations that increased the evoked overflow of tritium by 30%) were taken as a measure of affinity for the auto-receptors. The subclassification was based on a comparison of these affinity estimates with affinities for alpha 2A, alpha 2B, alpha 2C and alpha 2D radioligand binding sites and for previously classified alpha 2A- and alpha 2D-autoreceptors. The comparison indicates that the alpha 2-autoreceptors in the brain cortex of Cercopithecus aethiops belong to the genetic alpha 2A/D and not the alpha 2B or alpha 2C subtype. In their pharmacological properties, the autoreceptors are closest to the pharmacological alpha 2D subtype. The results support the notion that alpha 2-autoreceptors belong at least predominantly to the alpha 2A/D subtype of alpha 2-adrenoceptors.
Trendelenburg
A U
AU
Pharmakologisches Institut, Freiburg, Germany.
Sutej
I
I
Starke
K
K
D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D002522:Chlorocebus aethiops; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000378:metabolism; D011869:Radioligand Assay; D017661:Receptors, Presynaptic / Q000187:drug effects* / Q000378:metabolism
D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D017661:Receptors, Presynaptic; D009638:Norepinephrine