Morphological alterations of neurons and astrocytes and changes in emotional behavior in pentylenetetrazol-kindled rats

Changes of emotional behavior and neuronal cell loss in the hippocampus wer e investigated after pentylenetetrazol (PTZ) induced kindling in rats. Beha vioral and morphological changes were studied in partially and fully kindle d rats and after different postkindling periods comparing to the controls. The resident-intruder test indicated a diminished offensive behavior in par tially and fully kindled animals. The open-field and the cat-odor expositio n tests reveal changes in defensive behavioral pattern only in fully kindle d rats. A decrease of exploratory locomotion and an increase in freezing we re assessed in the open-field and the cat-odor exposition test, respectivel y, up to 10 weeks after the end of kindling. The first damaged neurons (CA4 region) were observed in the partially kindled group (PK), correlating wit h an increase in the glial fibrillary acidic protein (GFAP)-immunoreactivit y (GFAP-IR) and hypertrophy of astrocytes. The most significant increase in the number of damaged neurons was detected 24 h after completion of kindli ng (selective vulnerability: CA4/CA1 > DG>CA2 + CA3). The neuronal loss wen t on for 10 weeks postkindling. A low correlation between the number of Sta ge 4 kindling seizures and the number of damaged hippocampal neurons was fo und 24 h after the end of kindling in individual rats. The present results demonstrate that PTZ kindling goes along with long-lasting changes in emoti onal behavior. The alterations of the defensive behavior after the terminat ion of kindling can be interpreted as depression-like and are obviously ass ociated: with a characteristic pattern of neuronal loss in various hippocam pal regions. (C) 2001 Elsevier Science Inc. All tights reserved.