| Abstract No.: | C-E3162 |
| Country: | Canada |
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| Title: | DOPAMINE ANTAGONISM IN DORSAL STRIATUM BUT NOT NUCLEUS ACCUMBENS INTERACTS WITH ESTRADIOL TO AFFECT STRATEGY USE IN FEMALE RATS. |
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| Authors/Affiliations: | 1 Matthew Quinlan*; 1 Ivonne LaChapelle; 1 George Radiotis; 1 Meghen Caissie; 1 Wayne Brake;
1 Concordia University, Montreal, QC, Canada
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| Content: | OBJECTIVES: Previous research has demonstrated a role of estrogen (E) in the use of a particular cognitive strategy when solving a maze. For example, rats with high levels of E tend to use an allocentric (place) strategy while rats with low levels of E use an egocentric (response) strategy. However, the influence of E can not be considered the sole determinant of cognitive strategy utilization as our previous findings suggest an important role for dopamine (DA). Through the use of intraperitoneal (IP) injections of DA D1 receptor (D1R) and DA D2 receptor (D2R) antagonists it was demonstrated that the influences of DA and E interact and bias an animal towards use of a particular strategy. The goal of the present experiment was to determine whether DA interacts with E specifically in the striatum. Thus, D1R and D2R antagonists were microinjected into either the dorsal striatum or nucleus accumbens.
MATERIALS AND METHODS: 64 Sprague-Dawley adult female rats (250-300g) were trained and tested in a modified plus maze. All subjects were ovariectomized (OVX) and were implanted with cannulae bilaterally into either the dorsal striatum (AP -0.3, ML +/-4.0, DV -5.0) or the nucleus accumbens (AP -1.2, ML +/-1.8, 10°, DV, -6.8). Additionally, each subject received a daily dose of either high (~90pg/ml) or low (~32pg/ml) 17β-estradiol benzoate while performing the task for a reward (half of a Froot Loop®). Subjects received one daily session of 10 trials per day in which the reward was placed in either the left or right arm of the maze. In order to assess acquisition of the task, subjects were trained in the maze to a specific criterion level; 8/10 correct choices for three consecutive days. Upon achieving criterion, each subject received a probe trial in which all extra-maze cues remained static but the starting point was 180° opposite the original starting point. Additionally, subjects were administered microinjections of either D1R (SCH 23390; 0.1μl/ml and 0.01μl/ml) or D2R (raclopride; 2μl/ml and 0.5 0μl/ml) antagonists or a vehicle control (saline) at the rate of 0.5μl/ml/per side.
RESULTS: Microinjection of D1R but not D2R into the dorsal striatum causes a shift in strategy in both high and low E rats. That is, a majority of high E rats switched to using a response strategy and a majority of low E rats switched to using a place strategy. Conversely, the same microinjections into the nucleus accumbens resulted in rats having no significant change in strategy.
CONCLUSIONS: It appears that dorsal striatal dopamine acting at D1R interacts with estrogen to affect strategy use. On the other hand, dopamine antagonism in the nucleus accumbens has no effect on strategy use. |
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