9) received substantial inhibition in the opener phase and also exhibited postinhibitory rebound depolarization. Mutual inhibiting interneurons

that respond with postinhibitory rebound generate rhythmically alternating activity bursts (Perkel and Mulloney 1974; Satterlie 1985). Our data indicate that rebound from opener-phase inhibition triggers closer-interneuron spiking, which in turn temporarily inhibit Inhibitors,research,lifescience,medical opener interneurons during the closer phase. This would explain the tight latency coupling of wing-opener and wing-closer bursts in the motor pattern (Kutsch and Huber 1989). Only opener interneurons (e.g., A3-AO) showed small subthreshold depolarizations following the last syllable cycle

of the chirps, whereas in closer interneurons the depolarization of the last syllable in the chirp slowly decayed (e.g., Fig. 9A). This suggests that once a chirp has started, the alternate bursting of opener and closer interneurons continues until the opener neurons finally fail to generate Inhibitors,research,lifescience,medical a spike burst. Activated by tonic command neuron spike activity, the singing CPG generates Inhibitors,research,lifescience,medical the species-specific calling song pattern with 3–5 syllables grouped to chirps. Constant depolarizing current injection in A3-AO or T3-DO, however, elicited sustained syllable trains, which reliably reset the ongoing chirp rhythm. Subsequent to current elicited syllables, the next chirp always Inhibitors,research,lifescience,medical started after a regular chirp interval. This result contradicts the idea of an independent chirp-cycle generator that periodically drives or inhibits the syllable generating

circuit (Kutsch 1969; Bentley 1969). The chirp rhythm rather originates from activity-dependent inherent network and/or cellular properties (Bentley and Hoy 1972) that regularly silence the syllable generation and let it recover after a normal chirp interval. Additionally, the chirp pattern is stabilized by rhythmic biological activity feedback loops comprising interneurons of the subesophageal and posterior selleckchem abdominal Inhibitors,research,lifescience,medical ganglia (Otto and Hennig 1993; Schöneich and Hedwig 2011) and Entinostat also depends on the activity level of the descending command neurons (Hedwig 2000). Further studies are required to reveal the neural mechanism controlling chirp generation, which probably include activity-dependent slow changes of membrane conductances (El Manira et al. 1994; Harris-Warrick 2010) and/or periodical recovery of strongly depressing synapses (Manor and Nadim 2001). Future prospects Our identification of singing CPG neurons in Gryllus bimaculatus highlights the importance of ganglion A3. The data provide the basis for further studies to establish the functional circuitry of the network and to reveal evolutionary modifications in the singing CPG that account for the distinctive calling song patterns in related cricket species (Alexander 1962).