Ticks are strict blood-feeding arthropods (Acari) and have the potential to transmit disease agents (bacteria, parasites, viruses). Important gaps remain in our knowledge of the tick synganglion. Understanding of its activity in different conditions could foster the developement of tick-specific acaricides targetting neuroreceptors, or of alternatives to chemical treatments. We dissected synganglions of Ixodes ricinus adult ticks in different biological conditions (questing females or males, bloodfeeding females). This material was used for high throughput RNAseq, with a sequencing on one lane of an Illumina 4000 machine. Reads were de novo assembled, mapped on a draft genome sequence, and we then focused on the transcripts with coding potential (i.e. on predicted coding sequences, n=38,909). We obtained a tick synganglion transcriptome with a high level of gene completeness (as a result of high sequencing coverage), which also showed a high level of specificity when compared to previously published transcriptomes for I. ricinus. One puzzling result was the high frequency of tissue-specific transcripts corresponding to transposon related genes. We performed annotation and phylogenetic analyses of neuropeptides, neuropeptide receptors and neurotransmitter receptors. Notably, we achieved a near-exhaustive reconstruction of the Cys-loop Ligand-Gated Ion Channel genes (including the nAchr receptors), a first for any tick species, to our knowldege. We combined phylogenetic studies for each type of receptor with data on expression level in the different biological conditions, and on genomic localization. Populational variation was also explored, revealing highly significant polymorphisms in potential acaricidal targets