ACKNOWLEDGEMENTS

Thanks to The Foundation of Hope and NIAAA grant AA019682 to JB and the Bowles Center for Alcohol

Studies for making this work possible

INTRODUCTION

ARC EXPRESSION

CONCLUSIONS

POST 7-D CORT POST 21-D CORT

PROCEDURE

POST 14-D CORT

Stress has been shown to be a major predictor in the onset ofvarious neuropsychological disorders including majordepressive disorder (MDD). A core symptom of MDD isanhedonia or a loss of interest/pleasure in normally rewardingactivities. However little is known about how stress exposureduring the adolescent developmental period affects theemergence of anhedonia and how this differs from stressexposure in adulthood. Using an animal model we havepreviously shown anhedonic-like behavior in male adult ratsfollowing chronic exposure to the stress hormonecorticosterone (CORT). Thus, the aim of this work is to explorethe relationship between CORT exposure and anhedonic-likebehavior as measured by sucrose intake tests in adolescentand adult male rats. Adolescent (PND 28) and adult (PND 70)rats were exposed to CORT (0.3 mg/ml) for 21 days. Sucroseintake tests were conducted weekly to measure anhedonic-likebehavior. Here we show that chronic CORT exposure doesindeed predict a significant decrease in sucrose intake in adultmale rats; however, this effect was not observed in adolescentmale rats. These results suggest that there are underlyingmolecular mechanisms that protect adolescent male rats fromthe development of anhedonic-like behavior following CORTexposure. Immunohistochemical analyses of Arc expression-an immediate early gene and marker for neural plasticity-wereconducted to identify the underlying molecular mechanisms ofthis effect.

Figure 3: SI test conducted following 7 days of CORT and water exposurerevealed a significant decrease in sucrose intake among adult rats exposed toCORT but not water. This effect was not observed in adolescent rats. *p<0.05

Figure 5: SI test conducted following 21 days of CORT and water exposurerevealed a significant decrease in sucrose intake among adult rats exposed toCORT but not water. This effect was not observed in adolescent rats. *p<0.05

Figure 4: SI test conducted following 14 days of CORT and water exposure revealed asignificant decrease in sucrose intake among adult rats exposed to CORT but not water.This effect was not observed in adolescent rats. *p<0.05

Stress hormone exposure induces anhedonic-like behavior in adult male rats but not in adolescent rats.

B. Fortino, V. Agan, A.A. Jaramillo, J. BesheerBowles Center for Alcohol Studies, Department of Psychiatry, University of North Carolina at Chapel Hill

Psychology Department Sponsor: Dr. Charlotte Boettiger

PrL

Post 7-d CORT

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BL SISISI7-d CORT/H2O 14-d CORT/H2O 21-d CORT/H2O

Figure 1: Adolescent (PND 28) and adult (PND 70) male LongEvans rats were given a baseline (BL) sucrose intake (SI) test.Adult and adolescent rats were then given a bottle containing aCORT solution (0.3 mg/ml) or H2O for 21 days. Weekly sucroseintake (SI) tests were conducted

WEIGHTS

A B C

D

Figure 2: Daily average weight of adolescentand adult rats during water and CORTexposure did not differ among age group.

Figure 6: (A) Atlas of the prelimbic region (PrL) a subregion of the prefrontal cortex(PFC) illustrating the area for analysis; (B) Immunohistochemistry (IHC) stain ofadolescent PFC and (C) adult PFC showing Arc expression; (D) CORT exposure didnot affect Arc expression in the PFC. Adolescent rats displayed an overall greateramount of Arc expression in the PFC.

Ø Chronic CORT exposure produces a significant decrease in sucrose intake in adultmale rats, which is indicative of anhedonic-like behavior.

Ø However, this effect was not observed in adolescent male ratsØ Tissue analysis revealed overall greater Arc expression in adolescent vs. adult male

rats across both groups (CORT/H2O). Future work will examine other brain regions,such as the nucleus accumbens, and the amygdala.

Ø Further research should explore the effects of chronic CORT exposure in adolescenceand its potential effects on the emergence of anhedonic-like behavior in adulthood.

Exposure Day0 2 4 6 8 10 12 14 16 18 20 22

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Anhedonic-like behavior emerges following CORT (7 d) in adult rats

Anhedonic-like behavior persists following CORT (21 d) in adult rats

Anhedonic-like behavior persists following CORT (14 d) in adult rats

Adolescent Adult

Arc expression is not altered by CORT exposure