Hp. Jedema et al., Sensitization of norepinephrine release in medial prefrontal cortex: effect of different chronic stress protocols, BRAIN RES, 830(2), 1999, pp. 211-217
Previously, we demonstrated that continuous exposure of rats to cold (5 deg
rees C) for 2-3 weeks potentiates the increase in extracellular norepinephr
ine in the medial prefrontal cortex produced by acute tail shock. In the pr
esent study, we used in vivo microdialysis to examine whether this sensitiz
ation of evoked norepinephrine release also occurs in the medial prefrontal
cortex following exposure to other chronic stress protocols. Rats exposed
to 30 min of intermittent foot shock (0.6 mA) each day for 14 days, did not
exhibit a greater increase in extracellular norepinephrine in response to
acute tail shock. To determine whether this discrepancy between cold exposu
re and foot shock might be related to differences in the nature or the patt
ern of exposure to the chronic stressor, we also examined the effect of int
ermittent exposure to cold or continuous exposure to a foot shock protocol
on tail shock-evoked norepinephrine release. Sensitized norepinephrine rele
ase did not develop following either intermittent exposure to cold (5 degre
es C; 4 h/day for 14 days) or continuous exposure to a foot shock protocol(
0.6 mA trains at random intervals 24 h/day for 14 days), suggesting that bo
th the nature of the stressor as well as the pattern of exposure to the chr
onic stressor play a role in the development of sensitized norepinephrine r
elease. (C) 1999 Elsevier Science B.V, All rights reserved.