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The phototransduction mechanism of the extra-ocular photoreceptor cells Ip-2 and Ip-1 in the mollusc Onchidium ganglion was examined. Previous work showed that the depolarizing receptor potential of another extra-ocular photoreceptor cell, A-P-1 is produced by a decrease of the light-sensitive K+ conductance activated by a second messenger, cGMP and is(More)
Simple photoreceptors, namely photoresponsive neurons without microvilli and/or cilia have long been known in the central ganglion of crayfish, Aplysia, Onchidium and Helix. Recently, similar simple photoreceptors, ipRGCs were discovered in the mammalian retinas. A characteristic common to all of their photoreceptor potentials shows a slow kinetics and(More)
The internal messengers mediating the photocurrent of the molluscan extraocular photoreceptor, A-P-1, were examined. In the dark, pressure-injection of cGMP into the A-P-1, voltage-clamped at resting levels, produced a rapid outward current, associated with an increase in conductance. However, the cGMP-induced current and increase in conductance were(More)
The photoresponse of an extraocular photoreceptor, the photoresponsive neuron (A-P-1) in the abdominal ganglion of Onchidium verruculatum, was studied by using a voltage-clamp with two micropipettes and a monochromatic light. When the A-P-1 was voltage-clamped at resting membrane potential levels, light induced a slowly developing inward current which(More)
Simple photoreceptors, namely photoresponsive neurons, designated as A-P-1, Es-1, Ip-2 and Ip-1, exist in the sea slug Onchidium ganglion. Previous works has shown that, of these, Ip-2 and Ip-1 respond to light with a hyperpolarizing receptor potential, caused by the opening of light-dependent, cGMP-gated K+ channels, whereas A-P-1 and Es-1 are depolarized(More)
We report the first recordings of the light-sensitive channel which is active during dark and is closed by light in the Onchidium extra-ocular photoreceptor cells. This light-sensitive channel was K-selective and was not blocked by extracellular Ca2+ and Mg2+. Application of cyclic GMP to excised inside-out patches activated (opened) a channel that appeared(More)
Histamine elicited depolarization (excitation) in some neurons and hyperpolarization (inhibition) in other neurons of the central nervous system of the marine mollusc, Onchidium verruculatum. The histamine sensitive region was along the axon at some distance from the soma. H1-receptor blockers (SA-97 and mepyramine) suppressed the excitatory (H1) response(More)
Simple photoreceptors, namely intrinsically light-sensitive neurons without microvilli and/or cilia, have long been known to exist in the central ganglia of crayfish, Aplysia, Onchidium, and Helix. These simple photoreceptors are not only first-order photosensory cells, but also second-order neurons (interneurons), relaying several kinds of sensory synaptic(More)
A single BPSP (excitatory-inhibitory postsynaptic potential) was monosynaptically produced in an identified Onchidium neuron, Be-1, with a beating rhythm upon stimulation of the cardiac nerve. The BPSPs summated to produce an inhibition of long duration (ILD) upon blockage of the beating rhythm after repeated stimulation, so that the BPSPs seemed to be(More)
The simple photoreceptors Ip-1 and Ip-2 are intrinsically light-sensitive neurons that exist in the abdominal ganglion of the sea slug Onchidium verruculatum. Using isolated ganglia and semi-intact or intact animal preparations, the present studies examined the light-sensing and physiological roles of Ip-1 and Ip-2 cells, which respond jointly to light by(More)