[Abstract Title]. - Society for Neuroscience

Authors: *T. A. BEDROSIAN, S. M. CLINTON, A. D. ABRAHAM, S. J. WATSON, H.
AKIL;
Molec Behav Neurosci Inst., Univ. Michigan, Ann Arbor, MI
Abstract: Our laboratory has selectively bred rats which exhibit natural differences in locomotor
response to novelty. High Responder (HR) rats show exaggerated novelty-induced locomotion
compared to Low Responder (LR) animals which show little activity in a novel environment. HR
rats also exhibit enhanced aggression, impulsivity, psychostimulant self-administration, and
neuroendocrine stress reactivity, and decreased anxiety- and depression-like behavior compared
to LRs. Few studies have explored early environmental factors which may contribute to the
emergence of HR-LR traits. While our breeding studies point to the heritability of the HR/LR
traits, we also discovered important early life environmental factors, namely distinct HR vs. LR
maternal care styles, which may also contribute to the phenotypes. We found that LR dams are
generally more attentive to their pups (spending more time licking/grooming and arched-back
nursing) during the first 2 postpartum weeks compared to HR dams. HR mothers spent more
time engaged in self-directed behaviors such as eating, drinking, and self-grooming. The current
studies utilized a cross-fostering paradigm to determine how HR vs. LR maternal style impacts
offspring. In the first study, HR- and LR-bred pups were raised by their biological mother, or
fostered to an HR or LR foster mother. In a second study, we cross-fostered intermediate
responder (IR) rats which were created by interbreeding the HR/LR lines. IR rats typically
exhibit a behavioral phenotype which is intermediate compared to the extreme behavior of the
bred HR/LR lines. Adult offspring were tested to assess locomotor response to novelty, anxiety-
and depression-like behavior, and neuroendocrine stress reactivity. Cross-fostering had minimal
impact on pure-bred HR/LR offspring, most likely due to the strong genetic factors which have
been enriched over several generations of breeding. The IR offspring, on the other hand, were
more readily influenced by HR vs. LR maternal style, probably because their baseline behavioral
phenotype was more moderate. IR offspring raised by HR mothers showed slight, but
significantly increased locomotor response to novelty, reduced anxiety-like behavior, and
slightly exaggerated neuroendocrine sensitivity compared to IRs raised by LR mothers. Ongoing
studies will evaluate the neural underpinnings of these behavioral effects.
Disclosures: T.A. Bedrosian , None; S.M. Clinton, None; A.D. Abraham, None; S.J.
Watson, None; H. Akil, None.
Poster
283. Stress-Regulated Pathways II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 283.8/PP4
Topic: E.06.f. Stress modulated pathways