A hormone-activated central pattern generator for courtship.
BACKGROUND
Medicinal leeches (Hirudo spp.) are simultaneous hermaphrodites. Mating occurs after a stereotyped twisting and oral exploration that result in the alignment of the male and/or female gonopores of one leech with the complementary gonopores of a partner. The neural basis of this behavior is presently unknown and currently impossible to study directly because electrophysiological recording techniques disrupt the behavior.


RESULTS
Here we report that (Arg(8))-conopressin G and two other members of the oxytocin/vasopressin family of peptide hormones induce in Hirudo verbana a sequence of behaviors that closely mimic elements of spontaneous reproductive behavior. Through a series of progressively more reduced preparations, we show that one of these behaviors, a stereotyped twisting that is instrumental in aligning gonopores in preparation for copulation, is the product of a central pattern generator that consists of oscillators in ganglia M5 and M6 (the ganglia in the reproductive segments of the leech), and also in ganglion M4, which was not previously known to play a role in reproductive behavior. We find that the behavior is periodic, with a remarkably long cycle period of around five minutes, placing it among the slowest behavioral rhythms (other than diurnal and annual rhythms) yet described.


CONCLUSIONS
These results establish the leech as a new model system for studying aspects of the neuronal basis of reproductive behavior.
Wagenaar
Daniel A
DA
Broad Fellows Program and Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA. daw@caltech.edu
Hamilton
M Sarhas
MS
Huang
Tracy
T
Kristan
William B
WB
French
Kathleen A
KA
D000818:Animals; D001696:Biomechanical Phenomena; D055724:Electrophysiological Phenomena; D005260:Female; D017952:Ganglia, Invertebrate / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007447:Invertebrate Hormones / Q000494:pharmacology / Q000502:physiology*; D007865:Leeches / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D010121:Oxytocin / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology; D010456:Peptides, Cyclic / Q000494:pharmacology / Q000502:physiology; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*
D007447:Invertebrate Hormones; D010456:Peptides, Cyclic; C076621:conopressin G; C085335:annetocin; D010121:Oxytocin