Genes expressed in the adult brain of Drosophila and effects of their mutations on behavior: a survey of transmitter- and second messenger-related genes

Structural and functional conservation of serotonin receptors throughout evolution

Pharmacological studies as well as molecular cloning of serotonin receptors have revealed a multiplicity of receptor subtypes not only in mammals but also in molluscs and arthropods. Most of these receptors belong to the G protein-coupled receptor family and modulate levels of second messengers such as cAMP, IP3 and calcium. Rather than being specialized in a particular physiological function, a given receptor may be expressed in multiple neurons throughout the brain but always in the same compartment of these neurons. The 5HT1B receptor for example, is generally localized presynaptically on neuronal terminals where it inhibits neurotransmitter release. A widespread distribution of 5-HT receptors might explain how serotonin can modulate the multiple neuronal circuits which underlie complex behaviors.

Galanin message-associated Peptide-like immunoreactivity in the nervous system of the blowfly: distribution and chromatographic characterization

Galanin message-associated peptide (GMAP) is a flanking peptide in mammalian preprogalanin located C-terminally of galanin (GAL). GMAP-like immunoreactive (LI) material in the brain of the blowfly Phormia terraenovae was analysed by radioimmunoassay combined with reversed-phase high-performance liquid chromatography and immunocytochemistry and compared to GAL-LI material. A sensitive radioimmunoassay, developed against a species-conserved portion of mammalian GMAP (synthetic porcine GMAP(19-41)amide), was applied to serially diluted blowfly head extracts. High-performance liquid chromatography combined with radioimmunoassay showed that the GMAP-LI material eluted as several different components with one major component coeluting with the synthetic GMAP fragment. One GMAP-LI peak co-eluted with a GAL-LI component of the extract. By immunocytochemistry it was shown that a distinct set of GMAP-LI neurons and neurosecretory cells is present in the blowfly brain and thoracico-abdominal ganglion. About 150 GMAP-LI cell bodies were found in the brain, distributed in the protocerebrum, tritocerebrum and suboesophageal ganglion. Several hundred GMAP-LI cell bodies were detected in the medulla of the optic lobe. In the fused thoracico-abdominal ganglion there are about 70 GMAP-LI cell bodies distributed in a segmental fashion. Several of the GMAP-LI neurons also contain GAL-LI material whereas some do not. In addition, there are GAL-LI neurons that do not react with the GMAP antiserum. Some of the GMAP-LI interneurons and neurosecretory cells could be traced in detail enabling a resolution of putative sites of action of the peptide.

Of mice and flies: commonalities among 5-HT receptors

Pharmacological studies as well as molecular cloning of 5-HT receptors have revealed a multiplicity of receptor subtypes, not only in mammals but, as discussed in this review by René Hen, also in molluscs and arthropods. Most of these receptors belong to the G protein-coupled receptor family, and their mechanism of action involves modulating levels of second messengers such as cAMP, IP3 and Ca2+. Rather than being specialized in a particular physiological function, a given receptor may be expressed in multiple neurons throughout the brain but always in the same compartment in these neurons. The 5-HT1B receptor, for example, is generally localized presynaptically on neuronal terminals, where it inhibits neurotransmitter release. A widespread distribution of 5-HT receptors might explain how 5-HT can modulate the multiple neuronal circuits that underlie complex behaviours.