Coexistence of cholinergic and somatostatin receptors on astrocytes of rat CNS.

Electrophysiological studies have shown that somatostatin (SOM; 10(-8) and 10(-7) M) causes a hyperpolarization of the majority of astrocytes in explant cultures of rat spinal cord and cortex. When SOM and the cholinergic agonists muscarine and nicotine (10(-6) M) were tested on the same cell, all three compounds produced hyperpolarizations, suggesting a colocalization of functional cholinergic and SOM receptors on the glial membrane. Combined immunohistochemical and autoradiographic binding studies demonstrating that almost all astrocytes which were immunostained by the monoclonal muscarinic or nicotinic antibodies were also intensely labelled by 125I-SOM, provide further evidence for the coexistence of cholinergic and SOM receptors on astrocytes.