<p>Noradrenaline modulates mechanically evoked responses in the rat spinal dorsal horn: an in vivo patch-clamp study</p>

To know a functional role of inhibitory synaptic responses in transmitting noxious and innoxious information from the periphery to the rat spinal dorsal horn, we examined inhibitory postsynaptic currents (IPSCs) elicited in substantia gelatinosa (SG) neurons by mechanical stimuli applied to the skin using the newly developed in vivo patch-clamp technique. In the majority (80%) of SG neurons examined, a brush stimulus applied to the ipsilateral hind limb produced a barrage of IPSCs that persisted during the stimulus, while a pinch stimulus evoked IPSCs only at its beginning and end. The pinch-evoked IPSCs may have been caused by a touch that occurs at the on/off time of the pinch. The evoked IPSCs were blocked by either a glycine-receptor antagonist, strychnine (4 μM), or a GABAA-receptor antagonist, bicuculline (20 μM). All SG neurons examined received inhibitory inputs from a wide area throughout the thigh and lower leg. When IPSCs were examined together with excitatory postsynaptic currents (EPSCs) in the same neurons, a brush evoked a persistent activity of both IPSCs and EPSCs during the stimulus while a pinch evoked such an activity of EPSCs but not IPSCs. It is suggested that innoxious mechanical stimuli activate a GABAergic or glycinergic circuitry in the spinal dorsal horn. This inhibitory transmission may play an important role in the modulation of noxious information in the SG.

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Erratum: Corrigendum: Intravenous administration of lidocaine directly acts on spinal dorsal horn and produces analgesic effect: An in vivo patch-clamp analysis

Scientific Reports ◽

10.1038/srep46814 ◽

2017 ◽

Vol 7 (1) ◽

Author(s):

Miyuki Kurabe ◽

Hidemasa Furue ◽

Tatsuro Kohno

Keyword(s):

Patch Clamp ◽

Dorsal Horn ◽

Intravenous Administration ◽

Analgesic Effect ◽

Spinal Dorsal Horn ◽

Spinal Dorsal

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Intravenous administration of lidocaine directly acts on spinal dorsal horn and produces analgesic effect: An in vivo patch-clamp analysis

Scientific Reports ◽

10.1038/srep26253 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 13

Author(s):

Miyuki Kurabe ◽

Hidemasa Furue ◽

Tatsuro Kohno

Keyword(s):

Spinal Cord ◽

Patch Clamp ◽

Dorsal Horn ◽

Acute Pain ◽

Analgesic Effect ◽

Spinal Dorsal Horn ◽

Intravenous Lidocaine ◽

Spinal Dorsal ◽

Postsynaptic Currents

Abstract Intravenous lidocaine administration produces an analgesic effect in various pain states, such as neuropathic and acute pain, although the underlying mechanisms remains unclear. Here, we hypothesized that intravenous lidocaine acts on spinal cord neurons and induces analgesia in acute pain. We therefore examined the action of intravenous lidocaine in the spinal cord using the in vivo patch-clamp technique. We first investigated the effects of intravenous lidocaine using behavioural measures in rats. We then performed in vivo patch-clamp recording from spinal substantia gelatinosa (SG) neurons. Intravenous lidocaine had a dose-dependent analgesic effect on the withdrawal response to noxious mechanical stimuli. In the electrophysiological experiments, intravenous lidocaine inhibited the excitatory postsynaptic currents (EPSCs) evoked by noxious pinch stimuli. Intravenous lidocaine also decreased the frequency, but did not change the amplitude, of both spontaneous and miniature EPSCs. However, it did not affect inhibitory postsynaptic currents. Furthermore, intravenous lidocaine induced outward currents in SG neurons. Intravenous lidocaine inhibits glutamate release from presynaptic terminals in spinal SG neurons. Concomitantly, it hyperpolarizes postsynaptic neurons by shifting the membrane potential. This decrease in the excitability of spinal dorsal horn neurons may be a possible mechanism for the analgesic action of intravenous lidocaine in acute pain.

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