Cell swelling is one of the early cellular responses to injury.In many pathological conditions (e.g.ischemia,epilepsy,brain trauma,etc.),the concentration of extracellular glutamate and ammonia were greatly increased.Previous findings showed that both glutamate and ammonia could induce cytosolic swelling in astrocyte.We noticed that in addition to cytosolic swelling,1 mM glutamate and 5 mM ammonia triggered time and concentration dependent nuclear swelling in primary culture of astrocyte,and the swelling was reversible after removing exogenous glutamate or ammonia.In isolated astrocytic nucleus,glutamate induced nuclear swelling but ammonia induced nuclear shrinkage instead.Our findings demonstrated that glutamate could directly induce nuclear swelling in astrocyte,whereas ammonia-induced nuclear swelling in astrocyte might be an indirect metabolic effect.