INDUCTION OF FOS PROTEIN IN A MODEL OF CLOSED-HEAD INJURY IN RATS

The induction of Fos immunoreactivity in the pyriform cortex and the h ippocampal formation after closed head injury was determined and compa red to that seen following cortical needle injury in pentobarbital ana esthetized male rats. Robust Fos expression was observed in the ipsila teral pyriform cortex following both types of injury but was observed in the ipsilateral dentate gyrus only following closed head injury. Pr etreatment with the NMDA receptor blocker MK-801 eliminated closed hea d injury induced Fos expression in the pyriform cortex and attenuated that seen in the hippocampus. Similar amounts of Fos expression were o bserved in urethane anaesthetized lactating and nonlactating rats foll owing closed head injury. No gross behavioural impairments as reflecte d in body weight gain and locomotor activity were seen in animals subj ected to closed head injury. These results demonstrate that as with ot her forms of brain damage, closed head injury at levels that produce n o overt brain lesion nor gross behavioural impairment induce Fos expre ssion in the pyriform cortex and the dentate gyrus which is dependent on the activation of NMDA receptors. Further, this response to brain i njury is not modulated by lactation.