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KMID : 0603820090150030199
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Journal of Experimental & Biomedical Science
2009 Volume.15 No. 3 p.199 ~ p.205
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Effects of [D-Pen², D-Pen?]-enkephalin on the Neuronal Activity of Medial Vestibular Nuclear Neurons
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Jang Su-Jeong
Jeong Han-Seong
Park Jong-Seong
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Abstract
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This study was designed to investigate direct effects of [D-Pen², D-Pen?]-enkephalin, a δ-opioid receptor agonist on the neuronal activity of medial vestibular nuclear (MVN) neurons by whole-cell configuration patch clamp experiments. The spike frequency of MVN neuron was increased to 9.50±0.55 (P＜0.05) and 10.56±0.66 (P＜0.05) by 5 and 10 μM [D-Pen², D-Pen?]-enkephalin from the control level of 8.05±0.55 spikes/sec, respectively (n=18). The resting membrane potential of the neurons was increased to -37.86±0.92 and -36.97±0.97 (P＜0.05) from -38.74±1.13 ㎷ by 5 and 10 μM [D-Pen², D-Pen?]-enkephalin, respectively. The amplitude of afterhyperpolarization was decreased to 23.78±0.65 and 21.67±0.89 (P＜0.05) from 23.73±0.53 ㎷ by 5 and 10 μM [D-Pen², D-Pen?]-enkephalin, respectively. The spike width was changed to 2.22±0.08 and 2.24±0.07 from 2.20±0.08 ㎷ by 5 and 10 μM [D-Pen², D-Pen?]-enkephalin, respectively. After pretreatment of naltrindole, a highly selective δ-opioid receptor antagonist, [D-Pen², D-Pen?]-enkephalin did not change firing rate, resting membrane potential, afterhyperpolarization amplitude, and spike width of MVN neurons. The above experimental results suggest that [D-Pen², D-Pen?]-enkephalin increases the neuronal activity of MVN neurons via inhibition of calcium-dependent potassium currents underlying the afterhyperpolarization.
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KEYWORD
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Action potential, [D-Pen², D-Pen5]-enkephalin, Opioid, Vestibular nuclear neuron
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