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Blockade of progesterone-activated estrous behavior in rats by intracerebral anisomycin is site specific
Abstract:
The hypothesis that progesterone (P) activates estrous behavior in estrogen-primed female rats via a protein synthetic mechanism was examined. The protein synthesis inhibitor anisomycin was applied intracerebrally via 28-gauge bilateral implants to neural sites implicated in the mediation of estrous responsiveness. Results showed that anisomycin blockade of P-activated estrous behavior was neural site specific. Animals with anisomycin placed in the ventromedial hypothalamus (VMH) (n = 27) showed low levels of lordosis and solicitation behavior 4 h after the subcutaneous administration of 500 micrograms P, whereas animals with anisomycin implants in the preoptic area (n = 11) or the midbrain area in the region of the interpeduncular nucleus (n = 11) displayed high levels of estrous behavior. No deficits in open-field activity were observed following localized anisomycin treatment, and all animals appeared to be healthy. Results of the present study are consistent with the hypothesis that P acts to promote estrous behavior via a receptor-mediated genomic protein synthetic mechanism, and provide additional evidence that the VMH is the primary site of P action.
Insights
Progesterone activates female rat estrous behavior through a protein synthesis mechanism. This action is specific to the ventromedial hypothalamus (VMH), indicating its primary role in mediating this reproductive behavior.
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Behavioral Neuroscience
Background:
- Progesterone (P) is a key hormone regulating female reproductive behaviors.
- The precise neural mechanisms underlying progesterone's activation of estrous behavior are not fully elucidated.
- Previous research suggests a role for protein synthesis in hormone-mediated behaviors.
Purpose of the Study:
- To investigate the role of protein synthesis in progesterone-mediated estrous behavior in estrogen-primed female rats.
- To determine the specific neural sites where progesterone acts via protein synthesis to facilitate estrous behavior.
- To test the hypothesis that the ventromedial hypothalamus (VMH) is a critical site for progesterone's action.
Main Methods:
- Intracerebral administration of the protein synthesis inhibitor anisomycin via bilateral implants in specific brain regions.
- Subcutaneous administration of progesterone (500 micrograms) to estrogen-primed female rats.
- Assessment of estrous behaviors (lordosis, solicitation) and open-field activity.
Main Results:
- Anisomycin blockade of progesterone-induced estrous behavior was site-specific.
- Anisomycin in the VMH significantly reduced lordosis and solicitation behaviors.
- Anisomycin in the preoptic area or midbrain did not impair estrous behavior.
- No deficits in open-field activity were observed, indicating specific effects on reproductive behavior.
Conclusions:
- Progesterone activates estrous behavior through a receptor-mediated genomic protein synthetic mechanism.
- The ventromedial hypothalamus (VMH) is the primary neural site mediating progesterone's action on estrous behavior.
- These findings support the hypothesis that de novo protein synthesis in the VMH is essential for progesterone to facilitate sexual receptivity.