Mapping of serotonin, dopamine, and histamine in relation to different clock neurons in the brain of Drosophila

Abstract

Several sets of clock neurons cooperate to generate circadian activity rhythms in Drosophila melanogaster. To extend the knowledge on neurotransmitters in the clock circuitry, we analyzed the distribution of some biogenic amines in relation to identified clock neurons. This was accomplished by employing clock neuron-specific GAL4 lines driving green fluorescent protein (GFP) expression, combined with immunocytochemistry with antisera against serotonin, histamine, and tyrosine hydroxylase (for dopamine). In the larval and adult brain, serotonin-immunoreactive (-IR) neuron processes are in close proximity of both the dendrites and the dorsal terminals of the major clock neurons, the s-LN(v)s. Additionally, the terminals of the l-LN(v) clock neurons and serotonergic processes converge in the distal medulla. No histamine (HA)-IR processes contact the s-LN(v)s in the larval brain, but possibly impinge on the dorsal clock neurons, DN2. In the adult brain, HA-IR axons of the extraocular eyelet photoreceptors terminate on the dendritic branches of the LN(v)s. A few tyrosine hydroxylase (TH)-IR processes were seen close to the dorsal terminals of the s-LN(v)s, but not their dendrites, in the larval and adult brain. TH-IR processes also converge with the distal medulla branches of the l-LN(v)s in adults. None of the monoamines was detectable in the different clock neurons. By using an imaging system to monitor intracellular Ca(2+) levels in dissociated GFP-labeled larval s-LN(v)s, loaded with Fura-2, we demonstrated that application of serotonin induced dose-dependent decreases in Ca(2+). Thus, serotonergic neurons form functional inputs on the s-LN(v)s in the larval brain and possibly also in adults.

Circadian release of pigment‐dispersing factor in the visual system of the housefly, Musca domestica

“…In this region they receive photic inputs from the eyelet, not only in the fruit fly but also in the blowfly, and modulating input from serotoninergic interneurons (Yuan et al, 2005;Hamasaka and Nä ssel, 2006;Yasuyama et al, 2006). PDF terminals in the distal medulla may also be input sites for serotoninergic and dopaminergic neurons since their projections are adjacent to the PDF fibers (Hamasaka and Nä ssel, 2006). We have not found any evidence for input synapses directed to varicosities, including PDF-containing ones, either in conventionally fixed tissues and in immunostained preparations.…”

“…Interactions of PDH/PDF-ir neurons with other cells are poorly understood. In D. melanogaster dendrites of l-LN v s, located in the accessory medulla, have been proposed as input sites of these cells (Hamasaka and Nä ssel, 2006;Helfrich-Förster et al, 2007). In this region they receive photic inputs from the eyelet, not only in the fruit fly but also in the blowfly, and modulating input from serotoninergic interneurons (Yuan et al, 2005;Hamasaka and Nä ssel, 2006;Yasuyama et al, 2006).…”

Visualizing glutamatergic cell bodies and synapses in Drosophila larval and adult CNS

“…The LOC contains the terminals of the 12 cholinergic larval photoreceptor neurons (Yasuyama et al, 1995) contained in the larval optic nerve and the dendrites of several cells thought to play a role in larval circadian rhythm including the pigment-dispersing factor (pdf)-expressing LN v s and the serotonergic LP1 neuron (Hamasaka and Nä ssel, 2006). Recently an additional cha-Gal4-positive (cholinergic) neuron was found to have dendrites in the LOC (Iyengar et al, 2006).…”

“…4). The DN1 neurons may form synapses in the LOC (Hamasaka and Nä ssel, 2006) and therefore could be the source for some of the DVGLUT-positive terminals observed there. While this manuscript was under review, Hamasaka et al (2007) used this DVGLUT antibody to demonstrate the larval DN1 neurons are glutamatergic.…”

GABAB receptors play an essential role in maintaining sleep during the second half of the night in Drosophila melanogaster

“…Thus, the l-LN v neurons are anatomically well suited to modulate the activity of many neurons. In addition, their arborisations overlap with those of monaminergic neurons (Hamasaka and Nässel, 2006). Several studies show that they indeed receive dopaminergic, octopaminergic and GABAergic input and that they control the flies' arousal and sleep Parisky et al, 2008;Kula-Eversole et al, 2010;Shang et al, 2011).…”