| Abstract No.: | B-E2160 |
| Country: | Canada |
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| Title: | INFUSION OF THE DOPAMINE AGONIST APOMORPHINE TO THE MEDIAL PREOPTIC AREA FACILITATES APPETITIVE SEXUAL BEHAVIOURS OF FEMALE RATS. |
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| Authors/Affiliations: | 1 M. Dean Graham*; 1 Jim Pfaus;
1 Concordia University, Montreal, QC, Canada
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| Content: | Objectives: The medial preoptic area of the hypothalamus (mPOA) regulates the sexual behaviour of male and female rats. Electrolytic or neurotoxic lesions of the mPOA in males severely disrupt the initiation of copulatory behaviour, whereas lesions of this region in female rats abolish solicitational behaviours. The mPOA is a terminal region of the incertohypothalamic dopamine system. Dopamine agonists infused to the mPOA of males stimulate erection or ejaculation, depending on the dopamine receptor subtype stimulated. Moreover, dopamine release in the mPOA of male rats shows a phasic pattern during appetitive sexual responses, and a tonic pattern during copulation, similar to mesolimbic dopamine release in the nucleus accumbens. Virtually nothing is known about the role mPOA dopamine might play in the sexual behaviour of female rats. Therefore, the present study examined the effect of different doses of the mixed D1/D2 receptor agonist, apomorphine on both appetitive and consummatory aspects of female sexual behaviour in ovariectomized rats primed with estradiol benzoate (EB, 10 μg 48 h prior to each test) and progesterone (P, 500 μg 4 h before each test).
Materials and Methods: Long-Evans females were ovariectomized and given replacement hormone treatment with EB and P, prior to 4 preliminary tests of sexual behaviour at 4-day intervals. Females were then implanted surgically with guide cannulae aimed bilaterally at the mPOA. After recovery, females were placed back on the hormone priming regimen and given a baseline test of sexual behaviour 5 min after infusion of saline. Females then were infused with 3 doses of apomorphine, 50, 100, or 200 μg, in a randomized order, over the next three tests at 4-day intervals. A final saline baseline test was conducted 4 days after the last drug test to examine any drift of baseline due to hormone or drug treatment. Results: Relative to the saline baseline, females that received the low dose of apomorphine displayed a significant increase in appetitive behaviours (solicitations and hops and/or darts). Females in the other two dose groups did not display a significant increase in any sexual behaviour. No difference in consummatory behaviour (lordosis) was observed after any dose of apomorphine. Conclusions: These data indicate that agonist activity at dopamine receptors in the mPOA plays an important role in the generation of appetitive sexual responses in female rats.
Supported by NSERC (JGP)
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