Mytilus edulis pedal ganglia express mu opiate receptor transcripts exhibiting high sequence identity with human neuronal mu 1

Previous pharmacological and biochemical evidence suggests that mu-subtype opiate receptors are expressed in the mollusk Mytilus edulis (Bivalve), inc luding the organism's ganglia. In this study, we present molecular evidence of mu opiate receptor expression. Using primers derived from the human neu ronal mu l opiate receptor, we used reverse transcription-polymerase chain reaction (RT-PCR) to detect expression of mu transcripts from Mytilus pedal ganglia. Sequence analysis of the RT-PCR products revealed 95% identity wi th the neuronal human mu l receptor. Furthermore, interleukin-1 and morphin e exposure to excised pedal ganglia resulted in up- and down-regulation of the mu receptor transcripts, respectively. This study provides molecular ev idence that mu-type opiate receptors are expressed in molluscan ganglia, su ggesting that they first appear in invertebrate organisms and are retained during evolution. (C) 1999 Elsevier Science B.V. All rights reserved.