Sj. Chrapusta et al., EFFECTS OF SINGLE AND REPEATED FOOTSHOCK ON DOPAMINE RELEASE AND METABOLISM IN THE BRAINS OF FISCHER RATS, Journal of neurochemistry, 68(5), 1997, pp. 2024-2031
Changes in the tissue levels of 3-methoxytyramine (3-MT), 3,4-dihydrox
yphenylacetic acid (DOPAC), homovanillic acid (HVA), and dopamine in t
he frontal cortex, hypothalamus, nucleus accumbens, and striatum were
evaluated after 0.5-4 h of footshock (2 mA, for 3 s every 30 +/- 5 s)
in Fischer rats. 3-MT, DOPAC, and HVA levels in the four brain areas p
eaked at 0.5 h and in most cases returned to baseline values within 4
h. No changes were found in dopamine levels. Repeated footshock stress
was evaluated by administering 10 footshock sessions (0.5 h, two per
day for 5 days). At the end of the 10th footshock session, 3-MT levels
were higher than at the end of the first footshock session in three o
f the four brain regions, indicating sensitization of dopamine release
. No differences were found between the first and 10th footshock sessi
ons in DOPAC and HVA levels. Fourteen days after the 10th footshock se
ssion, the levels of 3-MT, DOPAC, and HVA were the same as in control
rats in all four brain regions, A 0.5-h footshock challenge presented
14 days after the 10th footshock session attenuated DOPAC levels in th
e hypothalamus and nucleus accumbens, In contrast, DOPAC and HVA level
s in the frontal cortex showed sensitization after footshock challenge
, and a similar trend was apparent for 3-MT levels, These results indi
cate that repeated footshock stress induces generalized sensitization
of dopamine release and turnover in some areas of the brain of Fischer
rats. This sensitization may persist in the cortical but not subcorti
cal dopamine neurons after discontinuation of the treatment.