Astrocytes from forebrain, cerebellum, and spinal cord differ in their responses to vasoactive intestinal peptide

Astrocytes from cortex, cerebellum, and spinal cord responded to isoproterenol and vasoactive intestinal peptide (VIP) with increases in intracellular cyclic AMP levels. The response to VIP was as great as that to isoproterenol in cortical astrocytes (180-fold and 185-fold, respectively), and the effect of VIP in combination with isoproterenol was partially additive. Spinal cord astrocytes also responded to VIP and isoproterenol with equal potency (seven- to ninefold and eight- to 13-fold, respectively), but the level of response was much smaller than in cortex. Spinal cord astrocytes were synergistic in their response to VIP and isoproterenol. The response to VIP was lowest in cerebellar astrocytes (only threefold), and no additivity was observed when VIP was added together with isoproterenol. A small response to alpha-melanocyte stimulating hormone (alpha-MSH) was also observed in cortex and cerebellum, but not in spinal cord. Somatostatin inhibited the response to isoproterenol in cortex and cerebellum, but had no effect in spinal cord. The results from the above study show that astrocytes obtained from these three regions of the rat CNS express quite different responses to VIP and alpha-MSH and further point to possible astrocyte heterogeneity.