Origin and classification of spontaneous discharges in mouse superficial dorsal horn neurons

Abstract

Superficial laminae of the spinal cord possess a considerable number of neurons with spontaneous activity as reported in vivo and in vitro preparations of several species. Such neurons may play a role in the development of the nociceptive system and/or in the spinal coding of somatosensory signals. We have used electrophysiological techniques in a horizontal spinal cord slice preparation from adult mice to investigate how this activity is generated and what are the main patterns of activity that can be found. The results show the existence of neurons that fire regularly and irregularly. Within each of these main types, it was possible to distinguish patterns of spontaneous activity formed by single action potentials and different types of bursts according to intra-burst firing frequency. Activity in neurons with irregular patterns was blocked by a mixture of antagonists of the main neurotransmitter receptors present in the cord. Approximately 82% of neurons with a regular firing pattern were insensitive to synaptic antagonists but their activity was inhibited by specific ion channel blockers. It is suggested that these neurons generate endogenous activity due to the functional expression of hyperpolarisation-activated and persistent sodium currents driving the activity of irregular neurons.

Discovering Effective Connectivity in Neural Circuits: Analysis Based on Machine Learning Methodology

“…Analysis were run with all afferents and we selected as target the afferent that produced better metrics. Neurons had a mean firing frequency of 0.9 ± 0.35 Hz (range 0.03–3.88 Hz) and their firing patterns were classed as irregular simple (10 units), irregular fast burst (2), and regular simple (1) following criteria previously reported ( Lucas-Romero et al, 2018 ). The afferent had an irregular firing pattern with a mean firing frequency of 0.09 Hz.…”

“…Experimental data were obtained from an in vitro experiment using a neonate mice spinal cord slice obtained as previously described ( Lucas-Romero et al, 2018 ). Briefly, the lumbar segments of the spinal cord were dissected from anesthetized animals (urethane 2 g/Kg i.p.)…”

“…In this way, we obtained simultaneous spike trains from a set of dorsal horn neurons and several primary afferents of which one was selected as target. The experiments recorded unperturbed spontaneous activity in absence of external stimulation ( Lucas-Romero et al, 2018 ).…”

Encoding of inflammatory hyperalgesia in mice spinal cord

“…Spontaneous activity of superficial dorsal horn neurons has been reported in several in vivo preparations (Hentall, 1977;Kumazawa and Perl, 1978;Sandkühler and Eblen-Zajjur, 1994) as well as in vitro preparations (Li and Baccei, 2011;Lucas-Romero et al, 2018;Roza et al, 2016).…”

Implication of Kv7 Channels in the Spinal Antinociceptive Actions of Celecoxib

“…For recordings of deep dorsal horn neurones, extracellular signals were preamplified Â10 (MPA81; Multichannel Systems, Reutlingen, Germany) and were further amplified Â500 with an 8-channel amplifier (Cyberamp; Molecular Devices) (Roza et al, 2016). In recordings from superficial dorsal horn neurones, the electrode was connected to a RHS2000 32-channel headstage containing two RHS2116 amplifier chips (Intan Technologies, Los Angeles, CA) (Lucas-Romero et al, 2018). The signals were band-pass filtered between 200-300 Hz and 3 kHz, digitized at 20 kHz (1401 Plus; CED), and stored for analysis.…”