Download document 8940063

Undergraduate
Category: Physical and Life Sciences
Degree Level: B.S. Behavioral Neuroscience
Abstract ID# 1080
Sex-Differences in the Effects of Adolescent Ethanol Exposure on Fear Behavior in
Adulthood and Corresponding Structural Changes in the Nucleus Accumbens
Rain Thomas, Mollee Farrell, Colin Rey, Tina Gruene, Rebecca Shansky
Introduction
100
80
60
60
40
40
40
20
20
20
0
100
100
80
80
3
2
2
1
EtOH males
CON males
1
Proximal
Proximal
2.5
2.0
2.0
1.5
1.5
1.0
0.5
0.0
Proximal
Distal
Distal
Female
Female
CON
EtOH
50 μm Methods: Cell Filling
0
Distal
Male
average of 3 tone
presentations
blocks of 2 tones
shock tone pairings
0
9
10
8
7
6
5
4
3
0
2
0
11
12
0
9
10
20
8
20
7
20
6
40
5
40
4
40
3
60
2
60
habituation
3
CON
EtOH
9
10
8
7
6
5
4
3
2
100
60
1
% freezing
80
Female
CON
EtOH
0
1
11
12
9
10
8
7
6
5
4
3
2
1
0
Spines/ µm
60
Male
Male
EtOH females
CON females
80
1
% freezing
Males
80
100
thin spines/ µm
100
Extinction retrieval
Results: Adolescent ethanol exposure does
not affect the distribution of nucleus
accumbens dendritic spines in adult rats
Spines/ µm
Extinction learning
Fear conditioning
Females
The adolescent brain undergoes rapid developmental changes, and adolescent alcohol
exposure (AAE) has negative effects that persist to adulthood. The nucleus accumbens
(NAcc), a brain region involved in reward and aversion, undergoes structural plasticity after
long-term alcohol consumption. It is unknown if there are lasting structural changes in the
NAcc due to AAE. Further, sex differences in NAcc structural plasticity after AAE have never
been investigated. Fear conditioning and extinction paradigms are often used to examine
aversion, and NAcc is implicated in brain circuitry underlying fear learning. Though AAE
affects fear retention in adult male rats, the effects of AAE on female fear behavior are
unknown. The present study investigated sex differences in AAE effects on fear conditioning,
extinction, and NAcc structural changes. Over 2 weeks, adolescent female and male rats
(P30) received eight i.p. injections of an ethanol solution. As a control, a separate group of
rats received saline injections following the same time course. Afterwards, animals remained
in their home cages undisturbed until behavioral testing began in adulthood. At P100, the
animals were tested on a three-day cued auditory fear conditioning and extinction paradigm.
Fear was measured by freezing, and the results were analyzed for sex-specific effects of
AAE. For structural analyses, neurons in NAcc were microinjected with Lucifer Yellow,
allowing for visualization of dendritic spines with confocal microscopy. Dendritic segments
were analyzed for spine density and morphology. Studying sex differences in fear behavior
and structural plasticity following AAE has important implications for the development of sexspecific intervention.
Results: Adolescent ethanol exposure does not affect fear or
extinction learning in adult rats
thin spines/ µm
Abstract
CON
EtOH
1.0
0.5
0.0
Proximal
Distal
Conclusions
• Ethanol administration has no effect on NAcc dendritic spine density or
morphology in adult male or female rats that underwent fear conditioning and
extinction learning.
• AAE also had no effect on fear behavior. Further research is necessary to
investigate whether morphology differences in females have functional
implications.
*
apical length (µm)
3000
Males CON
Males EtOH
Females CON
Females EtOH
2000
1000
0
The medial prefrontal cortex (mPFC) and
basolateral amygdala (BLA) are critical for fear
expression and suppression. The NAcc
projects to and receives projections from both
mPFC and BLA. Previous research from our
lab shows that AAE results in dendritic atrophy
within mPFC of adult females but not males.
Goal: The current study investigates sex differences in the effects of adolescent ethanol
exposure on fear conditioning and extinction in adulthood, as well as effects on dendritic spine
density and morphology of medium spiny neurons in the NAcc.
• Compared to previous findings, the animals in the present study showed poor
extinction. This could be due to general stress effects of i.p. injections. Future
research will include a handled control group to investigate this possibility.
Results: Adolescent ethanol exposure does not affect nucleus
accumbens dendritic spine density in adult rats
Neuronstudio rendering
Deconvolved image
Postnatal day timeline
100
101
102
Male
Female
2.0
Saline
adolescence
Nature reviews
neuroscience, 2001
adulthood
1.0
0.0
0.0
Stubby
BLA
FEAR
1.0
0.5
Mushroom
VTA
CON
EtOH
From Patten et al, Frontiers in Pediatrics, 2014
0.5
Thin
PL
IL
1.5
Spines/ µm
Spines/ µm
1.5
Ethanol
2.0
CON
EtOH
• The present study looked at random neurons
in the NAcc, but could label projections using
FastBlue and examine whether these
projections saw changes in morphology.
• To continue with the circuit, the ventral
tegmental area (VTA) has been seen to project FastBlue injections into the
to both the mPFC and the NAcc. Therefore,
nucleus accumbens (left
changes in the VTA can be explored.
panel) label ventromedial PFC
neurons (right panel) to show
• Finally, other methods for delivering ethanol,
PFC-accumbens projections.
including drinking (self-administration) and
inhaling ethanol vapors, can be examined.
Methods: Ethanol Administration and Behavior
30-44
Future Directions
References
Thin
Mushroom
Stubby
Bolland, Kathleen A., et al. "Trajectories of adolescent alcohol use by gender and
early initiation status." Youth & Society (2013): 0044118X13475639.
Patten, Anna R., et al. “A comparison of the different animal models of Fetal alcohol Spectrum
Disorders and their use in studying complex behaviors. Frontiers in Pediatrics (2014):
10.3389/fped.2014.00093.