Colocalization of cholinergic, adrenergic and peptidergic receptors on astrocytes.

By means of combined immunohistochemical and auto-radiographic techniques we have studied the colocalization of cholinergic, adrenergic and peptidergic binding sites on astrocytes in explant cultures of rat spinal cord, brain stem and cerebellum. Many astrocytes which were immunostained by the monoclonal muscarinic receptor antibody M 35 were also intensely labelled by 3H-noradrenaline, the beta-adrenergic antagonist 3H-dihydroalprenolol and the peptides 125I-angiotensin II, 125I-neuropeptide Y and 3H-bradykinin. Electrophysiological studies demonstrating that muscarine, the adrenergic agonists noradrenaline and isoprenaline as well as angiotensin II, neuropeptide Y and bradykinin affect the membrane potential of the same astrocytes provide further evidence for the coexistence of cholinergic, adrenergic and peptidergic receptors on astrocytes.