Spike-triggered dendritic calcium transients depend on synaptic activity in the cricket giant interneurons.
The relationship between electrical activity and spike-induced Ca2+ increases in dendrites was investigated in the identified wind-sensitive giant interneurons in the cricket. We applied a high-speed Ca2+ imaging technique to the giant interneurons, and succeeded in recording the transient Ca2+ increases (Ca2+ transients) induced by a single action potential, which was evoked by presynaptic stimulus to the sensory neurons. The dendritic Ca2+ transients evoked by a pair of action potentials accumulated when spike intervals were shorter than 100 ms. The amplitude of the Ca2+ transients induced by a train of spikes depended on the number of action potentials. When stimulation pulses evoking the same numbers of action potentials were separately applied to the ipsi- or contra-lateral cercal sensory nerves, the dendritic Ca2+ transients induced by these presynaptic stimuli were different in their amplitude. Furthermore, the side of presynaptic stimulation that evoked larger Ca2+ transients depended on the location of the recorded dendritic regions. This result means that the spike-triggered Ca2+ transients in dendrites depend on postsynaptic activity. It is proposed that Ca2+ entry through voltage-dependent Ca2+ channels activated by the action potentials will be enhanced by excitatory synaptic inputs at the dendrites in the cricket giant interneurons.
Ogawa
Hiroto
H
Department of Biology, Saitama Medical School, 981 Kawakado, Moroyama, Iruma-gun, Saitama 350-0496, Japan. hogawa@saitama-med.ac.jp
Baba
Yoshichika
Y
Oka
Kotaro
K
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology*; D003712:Dendrites / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D006135:Gryllidae / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D007395:Interneurons / Q000502:physiology*; D008297:Male; D013569:Synapses / Q000502:physiology*
D002118:Calcium