title: Serotoninergic innervation of the locust mandibular closer muscle modulates contractions through the elevation of cyclic adenosine monophosphate.
abstract: The mandibular closer muscles of the locust receive innervation that is immunoreactive for the putative transmitter 5-hydroxytryptamine (5-HT). Cobalt-labelling suggests that the origin of this innervation is a group of cells located anteriorly in the suboesophageal ganglion. Bath application of 5-HT while the muscles are active produces marked changes in the contractions, increasing their amplitude, rate of contraction, and rate of relaxation. Incubation of isolated muscles with 5-HT shows that this amine elevates the levels of the cyclic nucleotide cyclic adenosine monophosphate (cAMP). In addition compounds that artificially elevate the levels of cAMP in the muscle--3-isobutyl-1-methylxanthine (IBMX), forskolin, and the cAMP analogue 8-(4-chlorophenylthio) cAMP--mimic the actions of 5-HT, whereas a potent inhibitor of insect adenylate cyclase, adenosine, considerably delays the onset of the effects produced by 5-HT. The effects observed with 5-HT in the mandibular muscle are similar to those of octopamine in the locust extensor tibiae muscle, and it is possible that this is an analogous modulatory system.
authors.affiliation: Department of Biology, University of Waterloo, Ontario, Canada.
authors.forename: R A
authors.initials: RA
authors.lastname: Baines
authors.forename: N M
authors.initials: NM
authors.lastname: Tyrer
authors.forename: R G
authors.initials: RG
authors.lastname: Downer
mesh_terms: D000818:Animals; D000242:Cyclic AMP / Q000502:physiology*; D005260:Female; D006110:Grasshoppers / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008334:Mandible / Q000502:physiology*; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D009119:Muscle Contraction; D009132:Muscles / Q000166:cytology / Q000294:innervation* / Q000502:physiology; D012701:Serotonin / Q000502:physiology*
chemical_list: D012701:Serotonin; D000242:Cyclic AMP