Neuron-associated astroglial cells express beta- and alpha 1-adrenergic receptors in vitro

In vivo, astroglial cells are closely interrelated with neurons. The present studies were undertaken to determine if certain astroglial properties are influenced when maintained in a heterogeneous cellular environment. Astrocytes and neurons were co-cultured from hippocampal tissue and the parameters examined included astroglial morphology and expression of beta- and alpha 1-adrenergic receptors (AR). Astroglial cells exhibit an extremely elongated morphology when growing in direct contact with neurons. Astroglia growing under the same culture conditions, but not in direct contact with neurons, exhibited a polygonal morphology. One hundred percent of the elongated astroglia expressed the beta-AR with an average density of 1320 binding sites/1000 microns 2. In contrast, only 40-50% of these elongated astroglia expressed alpha 1-ARs. Our results indicate that astroglia, maintained in the presence of neurons, continue to express beta- and alpha 1-ARs. These results suggest that under in vivo conditions, where astroglia normally exist in close contact with neurons, astrocytes may express surface receptors which enable them to sense neuronal activity and to selectively respond to such activity. The elongated astroglia described here may exhibit morphological features more reminiscent to that which exists in vivo.