Journal of Neuroscience, Vol 15, 3583-3593, Copyright © 1995 by Society for Neuroscience
Increased expression of c-jun, junB, AP-1, and preproenkephalin mRNA in rat striatum following a single injection of caffeine
P Svenningsson, A Strom, B Johansson and BB Fredholm
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
The effect of a single injection of caffeine on the expression of c- fos,
c-jun, junB, and junD, on activator protein 1 (AP-1) and on the levels of
preproenkephalin mRNA in rat striatum was studied. Male rats were given
caffeine (25 mg/kg, 50 mg/kg, or 100 mg/kg, i.p.) and sacrificed at
different times (0.5, 1, 2, 4, or 8 hr) after administration. By using in
situ hybridization of adjacent sections we found a rapid, transient, and
dose-dependent increase of c-fos, c-jun, and junB by caffeine in striatum,
especially in the lateral part. The induction peaked after 1 hr, but
persisted for 2 hr, and in the case of junB for 4 hr. No induction of junD
was found. A strong induction of junB, a weak induction of c-fos and c-jun,
but not of junD, was seen in nucleus accumbens. Furthermore, by using gel
shift assay we found an induction of AP-1 by caffeine (100 mg/kg) in
striatum, which peaked 2 hr after administration and was clearly increased
after 4 hr. c-Fos, c- Jun, and JunB proteins were components of the AP-1.
There was also a dose-dependent induction of preproenkephalin mRNA, which
was most pronounced in the lateral and caudal part of striatum; the level
peaked 4 hr after injection and was still significantly increased after 8
hr. In a complementary study we could not find increased binding to the AP-
1-like site in the 5'-flanking sequence of proenkephalin following caffeine
treatment. The data show that a single dose of caffeine induces a
temporally and spatially characteristic pattern of c-fos, c- jun, and junB
induction, followed by changes in AP-1 and preproenkephalin mRNA. Thus, a
single dose of caffeine causes changes in gene transcription in the brain
that may be related to the adaptive changes that occur after caffeine
administration. However, a direct causal link between the immediate early
genes and enkephalin could not be proven.