Adrenergic regulation of intercellular communications between cultured striatal astrocytes from the mouse

The permeability of gap junctions in cultured striatal astrocytes was investigated by the scrape-loading/dyetransfer technique. Prolonged application of norepinephrine (NE) (10 microM) reduced by half the extent of dye (Lucifer yellow) spread. This effect was linked to the activation of alpha 1-adrenergic receptors since it was mimicked by methoxamine and antagonized by prazosin. The adenosine agonist 2-chloroadenosine (10 microM), which potentiates the NE-evoked activation of phospholipase C (PLC) in striatal astrocytes, also potentiated the NE-evoked closure of gap junctions, the effect being as important as that observed with the uncoupling agent octanol. Measurements of inositol phospholipid turnover performed in identical experimental conditions revealed a close relationship between the extent of PLC activation and the magnitude of the uncoupling process. The effect of NE was mimicked by both phorbol ester and arachidonic acid, suggesting that biochemical events linked to PLC stimulation such as protein kinase C activation and/or eicosanoid production are likely involved in the NE-induced uncoupling. In addition, in the presence of a cAMP phosphodiesterase inhibitor, the stimulation of beta-adrenergic receptors by isoproterenol (10 microM) led to a large increase in cAMP accumulation correlated with an extension of dye diffusion. This observation suggests that junctional permeability could also be controlled by a cAMP-dependent mechanism. Altogether these results indicate that intercellular communication between cultured astrocytes can be regulated by different second messenger pathways as a result of the action of neurotransmitters on their receptors.