Common Sensory Inputs and Differential Excitability of Segmentally Homologous Reticulospinal Neurons in the Hindbrain

Initiation of Mauthner- or Non-Mauthner-Mediated Fast Escape Evoked by Different Modes of Sensory Input

“…Simultaneous Ca 2ϩ imaging and whole-cell recording have demonstrated that the somatic Ca 2ϩ increase associated with an action potential is much larger than that with subthreshold depolarization (Smetters et al, 1999;Viana di Prisco and Alford, 2004;Berger et al, 2007). Single spiking of the M-cell is supported by the previous observations: (1) the M-cell is prevented from firing repetitively by a powerful recurrent feedback inhibitory circuit (Furukawa and Furshpan, 1963;Faber and Korn, 1978) and ex- pression of low-threshold potassium channels as shown in goldfish (Nakayama and Oda, 2004); (2) the recurrent inhibitory circuit was also demonstrated in both adult and larval zebrafish (Hatta and Korn, 1998;Takahashi et al, 2002); and (3) repetitive firing was observed in goldfish only when the recurrent inhibitory circuit or the low-threshold potassium channel was blocked pharmacologically (Furukawa et al, 1964;Nakayama and Oda, 2004).…”

“…The morphologically similar M-series neurons are referred to as the segmental homologs (Metcalfe et al, 1986) and are indicated to act as a functional unit in escape behavior (O'Malley et al, 1996;Liu and Fetcho, 1999;Nakayama and Oda, 2004).…”

“…The larvae were anesthetized with 0.01% MS222, reembedded in 3.5% agar, and immobilized with injection of D-tubocurarine chloride solution (3 mg/ml; Sigma-Aldrich) to prevent tail movement evoked by AD stimulation from injury to the spinal cord. To stimulate the axons of the M-series (Furshpan and Furukawa, 1962;Eaton and Farley, 1975;Takahashi et al, 2002;Nakayama and Oda, 2004), a bipolar tungsten electrode was placed on the spinal cord rostral to the OGB1-injected site through a small hole cut in the agar and bipolar pulsed currents were delivered (pulse duration, 80 s).…”

Auditory Input to CNS Is Acquired Coincidentally with Development of Inner Ear after Formation of Functional Afferent Pathway in Zebrafish

“…Zebrafish and goldfish use auditory information effectively to escape quickly from sudden stimuli or predators by firing the Mauthner cells (M-cells) in the hindbrain (Zottoli, 1977;Burgess and Granato, 2007;Kohashi and Oda, 2008). In adult goldfish, it has been established morphologically as well as electrophysiologically that the M-cell is directly innervated by the ipsilateral VIIIth nerve afferents (Furshpan, 1964;Nakajima, 1974;Lin and Faber, 1988;Nakayama and Oda, 2004;Szabo et al, 2006Szabo et al, , 2007. In zebrafish, sound-induced postsynaptic potentials have been recorded in the adult M-cell (Hatta and Korn, 1998), and the earliest contact of the VIIIth nerve afferents with the M-cell occurs at 23 h postfertilization (hpf) (Kimmel et al, 1990).…”

Effective Sensory Modality Activating an Escape Triggering Neuron Switches during Early Development in Zebrafish

“…In addition, the M-cell membrane expresses low-voltage-gated potassium channels (Nakayama and Oda, 2004). Developmental increases in potassium currents, as in the auditory brainstems of higher vertebrates (Howard et al, 2007;Nakamura and Takahashi, 2007), will also help decrease the membrane time constant at the depolarizing phase before action potential generation (Fukui and Ohmori, 2004;Gittelman and Tempel, 2006).…”