α 1- and α 2-adrenergic receptors in rat corpus striatum

Abstract

Rat corpus striatum contained α 2-adrenergic receptor which were labelled with [ 3H]clonidine (95 ± 6 fmol/mg protein). The affinity of these receptors ( K d = 1.3 to 3.6 nM) was similar to that found in cerebral cortex. Five days after kainic lesions, the number of α 2-adrenergic receptors had dropped by half, suggesting that their location might be neuronal. One month after lesions, the number of α 2-adrenergic receptors had risen to that of the controls and was higher after two months. This increase would suggest a glial localization of the α 2-adrenergic receptor. We have previously described the presence of α 2-adrenergic receptors in primary astrocyte cultures (Ebersolt et al., 1981). Rat corpus striatum contained less α 1-adrenergic receptors than α 2-adrenergic receptors. They were labelled with [ 3H]prazosin (28 ± 1.9 fmol/mg protein) and were only slightly altered 5 days after kainic acid lesions (−20%). In addition to these classical α 1-adrenergic receptors, rat corpus striatum also contained [ 3H]WB4101 binding sites having high affinity for WB4101 (2–5 nM) and norepinephrine (1 μM) but a very low affinity for prazosin (4.4 μM). The exact nature of these sites remains unknown.