4A). This reduced activity in one A3-AO neuron, however, did not affect the ongoing singing motor activity, indicating that the single A3-AO interneuron is not necessary for the cycle-by-cycle generation of the singing motor

pattern and the spike activity of the contralateral A3-AO neuron was presumably sufficient to transiently maintain the motor output. Interestingly, short hyperpolarizing selleckbio current pulses (−5 nA; 100–1000 msec duration) in the A3-AO dendrite were immediately followed by additional membrane potential Inhibitors,research,lifescience,medical oscillations in this neuron (Fig. 4B). Although the depolarization amplitudes of the post-hyperpolarization response were considerably smaller (2–6 mV) than the opener-phase depolarizations during fictive singing (20–25 mV), A3-AO generated a burst of 3–5 action potentials during each poststimulus depolarization, which elicited a corresponding sequence of selleck chemicals llc syllables in Inhibitors,research,lifescience,medical the motor pattern that reset the ongoing chirp rhythm (Fig. 4B). Figure 4 Effect of A3-AO hyperpolarization on fictive singing. (A) Sustained current

injection with −10 nA reduced and suppressed (asterisks) the spike activity of A3-AO without influencing the ongoing Inhibitors,research,lifescience,medical singing motor pattern; arrow indicates a 2-sec gap … The intracellular current injection experiments demonstrated the importance of A3-AO spike activity for the singing pattern generation. By gradual manipulation of its membrane potential, we asked if also subthreshold stimulation would modulate the singing activity. Ramp-like depolarizing and hyperpolarizing current with maximum amplitudes of only +0.5 nA and −0.5 nA was injected into the dendrite of A3-AO. This gently shifted the membrane potential of the neuron without changing the number of syllables per chirp (Fig. Inhibitors,research,lifescience,medical 5A) Inhibitors,research,lifescience,medical or even the spike activity underlying each syllable (A3-AO spikes per syllable: 0 nA, 4.7 ± 0.6; −0.5 nA, 4.7 ± 0.5; +0.5 nA, 4.6 ± 0.7; mean ± SD; N = 1, n = 25 each). The low-amplitude current injection did not influence the average chirp duration, which remained 176 ± 5 msec throughout the experiment. The duration of the chirp intervals (212 ± 18 msec; mean ± SD before

current injection), however, progressively decreased with increasing depolarization (199 ± 15 msec for 0.1–0.3 nA; 192 ± 13 msec for 0.3–0.5 nA), whereas moderate hyperpolarization had no effect (Fig. 5B). Similarly, the initial syllable Drug_discovery periods within the chirps were modulated by moderate depolarization but not by hyperpolarization (Fig. 5C). With increasing depolarization, the first syllable period in a chirp was lengthened by up to 4 msec, the second syllable period was shortened by up to 2 msec, and the following syllable periods did not change. These subtle modulations of the singing motor pattern indicate that the temporal structure of the motor output does not only depend on the spike activity but also on graded changes in the membrane potential of A3-AO.