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TRPV1-dependent regulation of synaptic activity in the mouse dorsal motor nucleus of the vagus nerve - PubMed

  • ️Tue Jan 01 2013

TRPV1-dependent regulation of synaptic activity in the mouse dorsal motor nucleus of the vagus nerve

Imran J Anwar et al. Front Neurosci. 2013.

Abstract

The dorsal motor nucleus of the vagus (DMV) is a key integrative point of the parasympathetic neuronal network localized in the dorsal vagal complex. Activity of neurons in the DMV is closely regulated by synaptic inputs, and regulation of excitatory and inhibitory synapsis by transient receptor potential vanilloid type 1 (TRPV1) has been demonstrated. Activation of TRPV1 by heat, protons, endovanilloids, endocannabinoids, and inflammatory mediators is well established. In our study we hypothesized that TRPV1 contributes to the synaptic transmission of DMV neurons at physiological range of temperature without additional stimuli. Using whole-cell patch-clamp recordings we evaluated the effect of a rapid increase of temperature on excitatory and inhibitory neurotransmission and the contribution of TRPV1 to this response. Rapid increase of temperature from 25 to 37°C increased the frequency of miniature excitatory post-synaptic currents (mEPSC) by 351.7%. The frequency of miniature inhibitory post-synaptic currents (mIPSC) also increased by 184.7%. 5'-iodoresiniferatoxin (5'-iRFT), a selective TRPV1 antagonist, prevented the increase of mEPSC and mIPSC frequency. In summary, our data demonstrate that at physiological range of temperature TRPV1 contributes to presynaptic neurotransmission of DMV neurons.

Keywords: TRPV1; dorsal motor nucleus of the vagus; miniature postsynaptic currents; whole-cell patch-clamp recording.

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Figures

Figure 1
Figure 1

Excitatory neurotransmission to DMV neurons is potentiated by TRPV1 at physiological temperatures. (A) Continuous recording of mEPSCs at 25°C (A) and after elevation of temperature from 25 to 37°C (A1) in TTX (1 μM). (B,C). Bar graph summarizing the effect of temperature on mEPSC frequency (B) and mEPSC amplitude (C). *Significance (p < 0.05).

Figure 2
Figure 2

TRPV1 antagonist prevents the potentiation of excitatory neurotransmission caused by TRPV1 activation to DMV neurons. (A) Continuous recording of mEPSCs in the presence of 5′-iRFT (1μM) and TTX (1μM) at 25°C (A) and after increase of temperature from 25°C to 37°C (A1). (B,C). The effect of TRPV1 antagonist on the increase of mEPSC frequency (B) and amplitude (C). (D–F). Summary for temperature response on mEPSC frequency (D), mEPSC amplitude (E), and total inward current (F) (n = 6). Black traces indicate control conditions. Red traces indicate recordings conducted in the presence of 5'-iRFT, a TRPV1 antagonist. Dashed-line indicates physiological temperature. *Significance (p < 0.05).

Figure 3
Figure 3

Inhibitory neurotransmission to DMV neurons is potentiated by TRPV1 at physiological temperatures. (A). Continuous recording of mIPSCs at 25°C (A) and after increase of temperature from 25 to 37°C (A1) in TTX (1 μM). (B,C). Bar graph summarizing the effect of temperature on mIPSC frequency (B) and mIPSC amplitude (C). *Significance (p < 0.05).

Figure 4
Figure 4

TRPV1 antagonist prevents the increase of inhibitory neurotransmission to DMV neurons caused by TRPV1 activation. (A). Continuous recording of mIPSCs in the presence of 5′-iRFT (1 μM) and TTX (1 μM) at 25°C (A) and after rise of temperature from 25 to 37°C (A1). (B,C). The effect of TRPV1 antagonist on the increase of mIPSC frequency (B) and amplitude (C) (red traces are recordings with 5′-iRFT). (D–F). Summary for temperature response on mIPSC frequency (D), mIPSC amplitude (E), and total outward current (F) (n = 7). Black traces indicate control conditions. Red traces indicate recordings conducted in the presence of 5′-iRFT, a TRPV1 antagonist. Dashed-line indicates physiological temperature. *Significance (p < 0.05).

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