Little is known of the action of nitric oxide (NO) at the synaptic level on identified interneurones in local circuits that process mechanosensory signals. Here, we examine the action of NO in the terminal abdominal ganglion of the crayfish Pacifastacus leniusculus, where it has modulatory effects on the synaptic inputs of 17 identified ascending interneurones mediated by electrical stimulation of a sensory nerve. To analyse the role of NO in the processing of sensory signals, we bath-applied the NO donor SNAP, the NO scavenger PTIO, the nitric oxide synthase (NOS) inhibitor l-NAME, the NOS substrate l-arginine, a cyclic GMP (cGMP) analogue, 8-Br-cGMP, and the soluble guanylate cyclase (sGC) inhibitor ODQ. The effects of these chemicals on the synaptic inputs of the interneurones could be divided into two distinct classes. The NO donor SNAP enhanced the inputs to one class of interneurone (class 1) and depressed those to another (class 2). Neither the inactive isomer NAP nor degassed SNAP had any effect on the inputs to these same classes of interneurone. The NO scavenger PTIO caused the opposite effects to those of the NO donor SNAP, indicating that endogenous NO may have an action in local circuits. Preventing the synthesis of NO using l-NAME had the opposite effect to that of SNAP on each response class of interneurone. Increasing the synthesis of endogenous NO by applying l-arginine led to effects on both response classes of interneurone similar to those of SNAP. Taken together, these results suggested that NO was the active component in mediating the changes in amplitude of the excitatory postsynaptic potentials. Finally, the effects of 8-Br-cGMP were similar to those of the NO donor, indicating the possible involvement of a NO-sensitive guanylate cyclase. This was confirmed by preventing the synthesis of cGMP by sGC using ODQ, which caused the opposite effects to those of 8-Br-cGMP on the two response classes of interneurone. The results indicate that a NO-cGMP signal transduction pathway, in which NO regulates transmitter release from mechanosensory afferents onto intersegmental ascending interneurones, is probably present in the local circuits of the crayfish.
The Integrative Biology of the Heart
We are pleased to welcome submissions to be considered for our upcoming special issue: The Integrative Biology of the Heart, guest edited by William Joyce and Holly Shiels. This issue will consider the biology of the heart at all levels of organisation, across animal groups and scientific fields.
JEB@100: an interview with Monitoring Editor John Terblanche
John Terblanche reveals how he narrowly avoided becoming a sports scientist and why he thinks phenotypic plasticity is the big question currently facing comparative physiologists. Find out more about the series on our Interviews page.
Vision 2024: Building Bridges in Visual Ecology
Early-career researchers can apply for funded places at our Vision 2024: Building Bridges in Visual Ecology. The event is organised by Eleanor Caves, Sonke Johnsen and Lorain Schweikert and being held at Buxted park 10-13 June 2023. Deadline 1 December 2023.
Reconciling the variability in the biological response of marine invertebrates to climate change
Drawing on work in reef-building corals, Zoe Dellaert and Hollie Putnam provide historical context to some of the long-standing challenges in global change biology that constrain our capacity for eco-evolutionary forecasting, as well as considering unresolved questions and future research approaches. Read the full Centenary Review Article here.
Sipping takes no effort for hovering hawkmoths
Hovering takes the most effort so how much energy does sipping require when hawkmoths hover? Next to nothing, apparently. Alexandre Palaoro & colleagues have discovered that the insects’ proboscises are incredibly wettable, drawing nectar along the length with no effort, giving them a free drink on the wing.
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