Astrocytes are the most numerous cell types within the central nervous system and perform a variety of tasks, from axon guidance and synaptic support, to the control of the blood brain barrier and blood flow. They contribute in maintaining homeostasis at the synapse, regulating neuronal signalling, protecting neurons from oxidative damage, and determining the fate of endogenous neural precursors. Astrocytes produce trophic factors, and eliminate neurotoxins and thus fulfil important protective and reparative functions. In addition, astrocytes regulate the recruitment and activity of infiltrating haematogenous cells through their expression of cytokines, proteases, protease inhibitors, adhesion molecules, and extracellular matrix components.

The regulation of astrocyte function is complex. Histamine importantly contributes in this process, acting on histamine H₁- and H₂-receptors, expressed on the astrocyte surface. Activation of histamine H₁-receptors leads to depolarisation and degradation of membrane inositol-lipids and production of inositol-3-phosphate and diacylglycerol and activation of protein-kinase C. Activation of histamine H₂-receptors succeed to hyperpolarisation, activation of adenilat-cyclase and production of cAMP. It has been found that histamine stimulates glycogen breakdown in astrocytes by activation of both H₁- and H₂-receptors. Thus, the histamine-induced glycogen breakdown may involve increases in cAMP formation, and in intracellular Ca²⁺ levels, this latter resulting mainly from H₁-mediated extracellular Ca²⁺ uptake.

Histamine enhances astrocytes proliferation and differentiation via activation of protein-kinase C, and changes of cytoskeleton and morphology of astrocytes. Via activation of histamine H₁-receptors, histamine stimulates production of neurotrophic factors like nerve growth factor. Histamine also importantly influences the immune response of astrocytes. It modulates the production of certain cytokines and interacts with them in their actions.