Transformation of normal resting astrocytes to reactive astrocytes after injury is a well-known phenomenon. Using immunofluorescent labelling methods, astrocytes in the ischemically and retrogradely/anterogradely damaged adult forebrain nuclei were shown to express substance-P immunoreactivity. In contrast, astrocytes were not immunostained for substance-P in the normal brain or undamaged areas. Since substance-P has been shown to regulate inflammatory, wound-healing and immune responses in the peripheral tissues, it is likely that this aberrant expression of substance-P immunoreactivity in reactive astrocytes may relate to similar functions in the central nervous system as in the peripheral tissues after injury.