Blocking synaptic transmission with tetanus toxin light chain reveals modes of neurotransmission in the PDF-positive circadian clock neurons of Drosophila melanogaster

Yujiro Umezaki, Kouji Yasuyama, Hideki Nakagoshi, Kenji Tomioka

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Circadian locomotor rhythms of Drosophila melanogaster are controlled by a neuronal circuit composed of approximately 150 clock neurons that are roughly classified into seven groups. In the circuit, a group of neurons expressing pigment-dispersing factor (PDF) play an important role in organizing the pacemaking system. Recent studies imply that unknown chemical neurotransmitter(s) (UNT) other than PDF is also expressed in the PDF-positive neurons. To explore its role in the circadian pacemaker, we examined the circadian locomotor rhythms of pdf-Gal4/. UAS-TNT transgenic flies in which chemical synaptic transmission in PDF-positive neurons was blocked by expressed tetanus toxin light chain (TNT). In constant darkness (DD), the flies showed a free-running rhythm, which was similar to that of wild-type flies but significantly different from pdf null mutants. Under constant light conditions (LL), however, they often showed complex rhythms with a short period and a long period component. The UNT is thus likely involved in the synaptic transmission in the clock network and its release caused by LL leads to arrhythmicity. Immunocytochemistry revealed that LL induced phase separation in TIMELESS (TIM) cycling among some of the PDF-positive and PDF-negative clock neurons in the transgenic flies. These results suggest that both PDF and UNT play important roles in the Drosophila circadian clock, and activation of PDF pathway alone by LL leads to the complex locomotor rhythm through desynchronized oscillation among some of the clock neurons.

Original languageEnglish
Pages (from-to)1290-1299
Number of pages10
JournalJournal of Insect Physiology
Volume57
Issue number9
DOIs
Publication statusPublished - Sep 1 2011

Keywords

  • Circadian clock
  • Constant light
  • Drosophila
  • Locomotor rhythm
  • Neuronal network
  • Neurotransmission
  • Pigment-dispersing factor

ASJC Scopus subject areas

  • Physiology
  • Insect Science

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