Evidence for the existence of galanin receptors on cultured astrocytes of rat CNS: colocalization with cholinergic receptors.
The cellular localization of binding sites for [125I]galanin was studied in explant cultures of rat neocortex, cerebellum, locus coeruleus and spinal cord by means by of autoradiography. Binding sites for the peptide were observed on a great number of astrocytes in all CNS regions studied. In addition to astrocytes, many neurones were intensely labelled by [125I]galanin. Binding of [125I]galanin (10(-8) M) to both astrocytes and neurones was markedly reduced or inhibited by the unlabelled peptide at high concentration (10(-6) M), suggesting 'specific' binding of the radioligand. Evidence for the colocalization of galanin and cholinergic receptors on astrocytes was provided by combined autoradiographic and immunohistochemical studies. Many astrocytes were labelled by [125I]galanin and immunostained with antibodies to either muscarinic or nicotinic receptors. Electrophysiological studies revealed that addition of galanin (10(-9) to 10(-7) M) to the bathing fluid caused a dose-dependent hyperpolarization of the majority of astrocytes studied. When galanin (10(-8) M) and the cholinergic agonists muscarine and nicotine (10(-6) M) were tested on the same astrocyte, all three compounds induced a hyperpolarization, suggesting a colocalization of functional galanin and cholinergic receptors on the glial membrane.
Hösli
E
E
Department of Physiology, University of Basel, Switzerland.
Ledergerber
M
M
Kofler
A
A
Hösli
L
L
D000818:Animals; D001253:Astrocytes / Q000737:chemistry*; D001345:Autoradiography; D001665:Binding Sites; D001921:Brain / Q000166:cytology*; D002478:Cells, Cultured; D019004:Galanin / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009116:Muscarine / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D051381:Rats; D011950:Receptors, Cholinergic / Q000032:analysis*; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone / Q000032:analysis*; D013116:Spinal Cord / Q000166:cytology*
D018721:Muscarinic Agonists; D018722:Nicotinic Agonists; D011950:Receptors, Cholinergic; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone; D009538:Nicotine; D009116:Muscarine; D019004:Galanin