Early postnatal stress alters the 5-HTergic modulation to emotional stress at postadolescent periods of rats.
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. (c) 2005 Wiley-Liss, Inc.
Department of Neuropharmacology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Machiko
M
Matsumoto
Kasane
K
Higuchi
Hiroko
H
Togashi
Hiroyo
H
Koseki
Taku
T
Yamaguchi
Manabu
M
Kanno
Mitsuhiro
M
Yoshioka
D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000009:adverse effects; D004644:Emotions / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000254:growth & development* / Q000378:metabolism / Q000503:physiopathology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D009434:Neural Pathways / Q000254:growth & development* / Q000378:metabolism / Q000503:physiopathology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013313:Stress Disorders, Post-Traumatic / Q000378:metabolism / Q000503:physiopathology; D013315:Stress, Psychological / Q000378:metabolism* / Q000503:physiopathology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists; D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin