Moreover, injecting virgin females with synthetic SP into the hemolymph increased memory performances at 24 hours to a level that was indistinguishable from that of mated females ( Fig. Females mated to mutant SP 0 males that do not produce SP displayed low LTM scores, similar to that of virgin females ( Fig. Because this demonstrates that LTM performance specifically increases through mating, we wondered whether SP was responsible for this effect. We also checked that virgin females responded normally to the sensory cues presented during training and found no differences in their responses to odors or electric shocks, as compared to mated females (table S1). Here, LT-ARM performances were indistinguishable between virgin and mated females (fig. Repeated, massed training cycles induce another form of consolidated memory called LT-ARM, which is formed independently of protein synthesis ( 19). This is restricted to the most salient information, and it is induced only through repeated and spaced training cycles ( 20). As in most other species, LTM formation in Drosophila is dependent on de novo protein synthesis. To test memory performance in Drosophila, we used classical associative conditioning in which an aversive olfactory memory is generated by pairing an odor with electric shocks ( 19). We found that virgin females have a strong deficit in aversive LTM, whereas memory performance increases after mating ( Fig. Mating allows aversive LTM formation by SP transfer Here, we bring closure to these uncertainties and demonstrate that the reproductive state in female Drosophila acts on long-term memory (LTM) mechanisms via the direct neuromodulatory activity of SP and MIP. Until now, the question of whether mating influences cognitive functions such as learning and memory has not been addressed. Furthermore, myoinhibitory peptides (MIPs), neuromodulators also known as allatostatin B, have been shown to activate the SPR in an interaction that mediates mating-dependent, but also mating-independent, functions such as food intake in the brain ( 16– 18). Nevertheless, a specific function has not yet been attributed to circulating SP within the CNS. The SPR is also widely expressed within the central nervous system (CNS), and SP is proposed to circulate within the hemolymph in mated females and to cross the blood-brain barrier ( 9). The described postmating switch is mediated by SPR-expressing cells, specifically a subpopulation in the fly uterus called SP-sensing neurons (SPSNs) ( 12, 14). Once transferred to females, the SP acts via the SP receptor (SPR), a G protein–coupled receptor that is coupled to the inhibitory subunit α i and/or α o ( 15).
#Creative memories catalog 2011 full#
While the sensory pathway of SP signaling in Drosophila females has been intensively studied ( 12, 13), a full picture of how higher-order neurons in the brain coordinate the sensory integration of the postmating response is still pending ( 13, 14). All these changes are mediated by a sperm-bound peptide, the sex peptide (SP), which is transferred into the female’s reproductive tract during mating ( 9, 12). However, the mechanisms underlying these behaviors remain to be shown.Īfter copulation, females of the fruit fly Drosophila melanogaster undergo a variety of behavioral changes ( 3), including the rejection of subsequent mating partners ( 8), an increase in egg production and oviposition ( 9), and changes in sleep and activity patterns ( 10) as well as dietary preferences ( 11). These promoted behaviors could include spatial orientation and the ability to remember the location of food and water sources, as well as a decrease in risk-taking behavior ( 5, 7).
On the other hand, it has been proposed that the physiological and morphological adaptations of the brain during pregnancy and early motherhood lead to a selective decline in brain functions, while those adaptations serving maternal and fetal survival are promoted ( 1, 5, 6). Because fetus development demands high energy resources, costly brain functions in women could be sacrificed to realize a trade-off in energy supply between the mother and fetus during pregnancy ( 1). One long-debated hypothesis states that women face a decline in cognitive functions such as memory and attention during pregnancy ( 4). Nevertheless, the impact of mating on cognitive functions remains poorly studied. More generally, reproduction in all animals, including insects, is associated with the energetic costs of fetus or egg development and behavioral changes that serve the survival of the offspring ( 2, 3). Pregnancy and the postpartum period in mammalian females are associated with noticeable physiological and behavioral adaptations, along with fundamental changes in the hormonal regulation of brain functions ( 1).
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