Abstract
The 5-HT7 receptor remains one of the less well characterized serotonin receptors. Although it has been demonstrated to be involved in the regulation of mood, sleep, and circadian rhythms, as well as relaxation of vascular smooth muscles in mammals, the precise mechanisms underlying these functions remain largely unknown. The fruit fly, Drosophila melanogaster, is an attractive model organism to study neuropharmacological, molecular, and behavioral processes that are largely conserved with mammals. Drosophila express a homolog of the mammalian 5-HT7 receptor, as well as homologs for the mammalian 5-HT1A, and 5-HT2, receptors. Each fly receptor couples to the same effector pathway as their mammalian counterpart and have been demonstrated to mediate similar behavioral responses. Here, we report on the expression and function of the 5-HT7Dro receptor in Drosophila. In the larval central nervous system, expression is detected postsynaptically in discreet cells and neuronal circuits. In the adult brain there is strong expression in all large-field R neurons that innervate the ellipsoid body, as well as in a small group of cells that cluster with the PDF-positive LNvs neurons that mediate circadian activity. Following both pharmacological and genetic approaches, we have found that 5-HT7Dro activity is essential for normal courtship and mating behaviors in the fly, where it appears to mediate levels of interest in both males and females. This is the first reported evidence of direct involvement of a particular serotonin receptor subtype in courtship and mating in the fly.
Highlights
Serotonin (5-HT) is a monoamine neurotransmitter that regulates a variety of behaviors and physiological processes including circadian rhythms, sleep, appetite, aggression, locomotion, perception and sexual behavior in mammals [1,2]
Because of the potential role of the receptor in courtship, as described we examined 5-HT7Dro-GAL4 expression in relation to the male form of Fruitless (FruM), a key protein involved in sexual behaviors
Using our 5-HT7Dro-GAL4 driver to drive expression of a UAS-mCD8::GFP transgene, we have found GFP expression in third larval instar brain localized to discreet circuits within the brain hemispheres, as well as to specific neurons in the ventral ganglion
Summary
Serotonin (5-HT) is a monoamine neurotransmitter that regulates a variety of behaviors and physiological processes including circadian rhythms, sleep, appetite, aggression, locomotion, perception and sexual behavior in mammals [1,2]. They are, found both pre- and postsynaptically in the SCN [5]. 5-HT7 receptors modulate neuronal function in a number of areas of the brain that have been implicated in this behavior, including the SCN, DRN, thalamus and hippocampus [14]. 5-HT7 receptors have been implicated in the regulation of mammalian sexual behavior Activation of this receptor in rats mediates an inhibitory effect of female sexual behavior [15]
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