Involvement of the ryanodine receptor in morphologic modification of Hermissenda type B photoreceptors after in vitro conditioning.
We examined whether Ca(2+) induced Ca(2+) release through ryanodine receptors is involved in the conditioning of specific morphologic changes at the axon terminals of type B photoreceptors in the isolated circumesophageal ganglion of Hermissenda. Calcium chelation by bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid prevented the conformational change at the terminals after five paired presentations of light and vibration, which produce terminal branch contraction of B photoreceptors. Two ryanodine receptor blockers, dantrolene and micromolar concentrations of ryanodine, depressed the increase in excitability due to in vitro conditioning and the increase in intracellular Ca(2+) in response to membrane depolarization. Although the ability to increase intracellular Ca(2+) was depressed, synaptic transmission was preserved in the normal state from hair cells under dantrolene and ryanodine incubation. Ryanodine receptor blockers also prevented contraction at the B photoreceptor axon terminals. These results suggest that the ryanodine receptor has a crucial role in inducing the in vitro conditioning specific changes both physiologically and morphologically, including "focusing" at the B photoreceptor axon terminal.
Kawai
Ryo
R
Laboratory of Neurobiological Engineering, Department of Biological Science and Technology, School of High-Technology for Human Welfare, Tokai University, Numazu 410-0321, Shizuoka, Japan.
Horikoshi
Tetsuro
T
Sakakibara
Manabu
M
D000818:Animals; D002118:Calcium / Q000502:physiology; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D003620:Dantrolene / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008974:Mollusca; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D012433:Ryanodine / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*
D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D003620:Dantrolene; D002118:Calcium