Aims

To support the free and open dissemination of research findings and information on alcoholism and alcohol-related problems. To encourage open access to peer-reviewed articles free for all to view.

For full versions of posted research articles readers are encouraged to email requests for "electronic reprints" (text file, PDF files, FAX copies) to the corresponding or lead author, who is highlighted in the posting.

___________________________________________

Wednesday, December 22, 2010

Early Adolescence as a Critical Window During Which Social Stress Distinctly Alters Behavior and Brain Norepinephrine Activity



Many neural programs that shape behavior become established during adolescence. Adverse events at this age can have enduring consequences for both adolescent and adult mental health. 

Here we show that repeated social stress at different stages of adolescent development differentially affects rat behavior and neuronal activity. 

Early-adolescent (PND 28, EA), mid-adolescent (PND 42, MA), and adult (PND 63) rats were subjected to resident-intruder social stress (7 days) and behavior was examined 24–72h later. 

In EA rats selectively, resident-intruder stress increased proactive responses in the defensive burying and forced swim tests. 

In adult rats, resident-intruder stress decreased burying behavior regardless of whether the animal was stressed as an adult or during early adolescence. 

As the locus coeruleus (LC)–norepinephrine system has been implicated in proactive defense behaviors, LC neuronal activity was quantified in separate cohorts. 

Stressed EA rats had elevated spontaneous LC discharge rates and diminished responses to sensory stimuli compared with controls. 

Microinjection of a CRF antagonist into the LC selectively inhibited neurons of stressed EA rats, suggesting that EA social stress induces tonic CRF release onto LC neurons, shifting the mode of discharge to an activated state that promotes active defensive behaviors. 

In all adult groups, resident-intruder stress resulted in an increased phasic response to sensory stimuli with no change in spontaneous rates. 

MA was a transition period during which social stress did not affect behavior or LC activity. 

The results suggest that social stress interacts with the brain norepinephrine system to regulate defensive strategies in an age-dependent manner.




Read Full Dissertation    (PDF)