Magnesium activation of GTP hydrolysis or incubation in S-adenosyl-L-methionine reverses iron-56-particle-induced decrements in oxotremorine enhancement of K+-evoked striatal release of dopamine
Ja. Joseph et al., Magnesium activation of GTP hydrolysis or incubation in S-adenosyl-L-methionine reverses iron-56-particle-induced decrements in oxotremorine enhancement of K+-evoked striatal release of dopamine, RADIAT RES, 152(6), 1999, pp. 637-641
Previous research has determined that the deficits in motor behavior seen i
n aged animals irradiated with Fe-56 particles involved alterations in musc
arinic receptor sensitivity. In the present experiments, we determined whet
her increasing either membrane fluidity by exposure of striatal slices from
irradiated (56Fe particles) animals to S-adenosyl-L-methionine (SAM) or GT
P hydrolysis with Mg2+ would reverse this Fe-56-particle-induced loss of mu
scarinic receptor sensitivity, as has been observed in aged animals. Result
s indicated that, while increasing Mg2+ concentrations in the incubation me
dium was effective in reducing the radiation effects, SAM was able to effec
t some reversal of the radiation effects only at the lower concentration (2
00 mu M). These results suggest that similar mechanisms may be involved in
the deficits in signal transduction seen after Fe-56-particle irradiation t
o those seen in aging, and that these may include changes in the membrane s
tructure or composition that could alter subsequent responsiveness of trans
duction pathways. The results further suggest that, as has been reported pr
eviously, Fe-56-particle irradiation may accelerate brain aging, and that s
ince these HZE particles contribute at least 1% of the dose that astronauts
would receive from cosmic rays, long-term exposure on extended space fligh
ts (e.g. to Mars) may produce similar deficits that could have immediate or
delayed effects on behavior. (C) 1999 bg Radiation Research Society.