The biological clock depends on spontaneously firing neurons of the suprachiasmatic nucleus (SCN). Several ion channels, including L-type calcium channels, Ih, and subthreshold TTX-sensitive sodium channels, have been nominated for the spontaneous interspike "pacemaker" current that drives spontaneous firing. To distinguish between these candidates, Jackson et al. recorded from dissociated SCN neurons in current clamp and then used the firing pattern of each cell as a voltage command. When the sodium current was blocked, L-type channels were only able to support slow oscillations at more depolarized potentials.
2.The Who's Who Signal in Electric Fish
Bruce A. Carlson and Masashi Kawasaki
The African fish Gymnarchus niloticus uses a weak, quasisinusoidal electric organ discharge (EOD) to both communicate and navigate. The problem is that if neighbors use the same signal, it creates a serious "who's who" problem. The fish deal with this by shifting the frequency of their EOD, the "jamming avoidance response."