Meiser, Sonja and Ashida, Go and Kretzberg, Jutta (2019) Non-synaptic plasticity in leech touch cells. Frontiers in physiology, 10. p. 1444. ISSN 1664-042X

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Abstract

The role of Na+/K+-pumps in activity-dependent synaptic plasticity has been described in both vertebrates and invertebrates. Here, we provide evidence that the Na+/K+-pump is also involved in activity-dependent non-synaptic cellular plasticity in leech sensory neurons. We show that the resting membrane potential (RMP) of T cells hyperpolarizes in response to repeated somatic current injection, while at the same time their spike count (SC) and the input resistance (IR) increase. Our Hodgkin–Huxley-type neuron model, adjusted to physiological T cell properties, suggests that repetitive action potential discharges lead to increased Na+/K+-pump activity, which then hyperpolarizes the RMP. In consequence, a slow, non-inactivating current decreases, which is presumably mediated by voltage-dependent, low-threshold potassium channels. Closing of these putative M-type channels due to hyperpolarization of the resting potential increases the IR of the cell, leading to a larger number of spikes. By this mechanism, the response behavior switches from rapidly to slowly adapting spiking. These changes in spiking behavior also effect other T cells on the same side of the ganglion, which are connected via a combination of electrical and chemical synapses. An increased SC in the presynaptic T cell results in larger postsynaptic responses (PRs) in the other T cells. However, when the number of elicited presynaptic spikes is kept constant, the PR does not change. These results suggest that T cells change their responses in an activity-dependent manner through non-synaptic rather than synaptic plasticity. These changes might act as a gain-control mechanism. Depending on the previous activity, this gain could scale the relative impacts of synaptic inputs from other mechanoreceptors, versus the spike responses to tactile skin stimulation. This multi-tasking ability, and its flexible adaptation to previous activity, might make the T cell a key player in a preparatory network, enabling the leech to perform fast behavioral reactions to skin stimulation.

Item Type:	Article
Additional Information:	Publiziert mit Hilfe des DFG-geförderten Open Access-Publikationsfonds der Carl von Ossietzky Universität Oldenburg.
Uncontrolled Keywords:	invertebrate, mechanoreceptor, sodium–potassium pump, Hodgkin–Huxley neuron model, M-type KC current, spike count, resting potential, input resistance
Subjects:	Science and mathematics > Life sciences, biology Science and mathematics > Animals (zoology)
Divisions:	Faculty of Medicine and Health Sciences > Department of Neuro Sciences
Date Deposited:	29 Apr 2020 08:13
Last Modified:	29 Apr 2020 11:24
URI:	https://oops.uni-oldenburg.de/id/eprint/4390
URN:	urn:nbn:de:gbv:715-oops-44712
DOI:	10.3389/fphys.2019.01444
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