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Early postnatal stress alters the 5‐HTergic modulation to emotional stress at postadolescent periods of rats
Author(s) -
Matsumoto Machiko,
Higuchi Kasane,
Togashi Hiroko,
Koseki Hiroyo,
Yamaguchi Taku,
Kanno Manabu,
Yoshioka Mitsuhiro
Publication year - 2005
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.20100
Subject(s) - psychology , neuroscience , hippocampal formation , long term potentiation , agonist , synaptic plasticity , electrophysiology , receptor , medicine
Several lines of evidence have shown that traumatic events during the early postnatal stage might precipitate long‐lasting alteration in the functional properties underlying emotional expression. The aim of the present study was to examine whether the early postnatal stress alters the 5‐HTergic mechanism underlying regulation of emotional stress, focusing on the 5‐HT 1A receptor‐mediated synaptic responses in adult rats. Pups were exposed to aversive stimulus, footshock (FS) at the postnatal period of the second (2W) and the third week (3W). At postadolescent period (10–12‐week‐old), electrophysiological and behavioral studies were performed. The 5‐HT 1A receptor agonist tandospirone (10 mg/kg body wt, i.p.) blocked the long‐term potentiation (LTP) in the hippocampal CA1 field of 3W‐FS, as well as non‐FS control, whereas this inhibition was not observed in 2W‐FS group. Fear‐related freezing behavior observed during exposure to contextual fear conditioning markedly attenuated in 2W‐FS, but not in 3W‐FS. These data suggest that aversive stress exposed at 2W is attributable to changes in the 5‐HT 1A receptor‐mediated synaptic plasticity, which may be responsible for the attenuation of freezing behavior. Thus, 5‐HT 1A receptors appear to play a key role in the 5‐HTergic mechanism underlying regulation of emotional stress on the postnatal development of the brain. In other words, the second postnatal week may be the “critical period” for establishing proper behavioral responses to emotional stress in adult rats. © 2005 Wiley‐Liss, Inc.