INCREASE IN CORTICAL PROCHOLECYSTOKININ GENE-EXPRESSION INDUCED BY A MENINGO-CORTICAL INJURY - STUDIES ON THE INVOLVEMENT OF THE IMMEDIATE-EARLY GENE C-FOS

In rat cortex, a meningo-cortical injury causes complex changes in the expression of the ''immediate early'' genes c-fos and c-jun as well a s the neuropeptide gene procholecystokinin. Within 1 h, mRNA levels of c-fos and c-jun are enhanced. Three hours later they have returned to control values. Twenty-four hours after the injury, there is a second rise in the level of c-fos mRNA, which is accompanied by an increase in procholecystokinin-mRNA. In the present study, it was investigated whether these events are causally connected. When MK-801 (1.5 mg/kg), an ion-channel blocker, was injected 7 and 19 h after the injury, i.e. after the first rise in expression of both ''immediate early'' genes, it prevented the later increase in procholecystokinin-mRNA. When give n 30 min prior to the injury, MK-801 (4 mg/kg) prevented the increased expression of c-fos but did not affect the later rise in procholecyst okinin-mRNA. In a third experiment the cortex injury was performed in a manner which did not increase procholecystokinin-mRNA in frontal cor tex. Nevertheless, expression of the c-fos gene was enhanced when dete rmined 24 h after the operation. It is concluded that the injury-induc ed rise in the expression of the procholecystokinin gene is not connec ted with the changes in c-fos-mRNA.