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. 1994 Sep;113(1):303–309. doi: 10.1111/j.1476-5381.1994.tb16209.x

Inhibition by opioids acting on mu-receptors of GABAergic and glutamatergic postsynaptic potentials in single rat periaqueductal gray neurones in vitro.

B Chieng 1, M J Christie 1
PMCID: PMC1510063  PMID: 7812626

Abstract

1. Membrane properties of rat periaqueductal gray neurones were investigated by use of intracellular recordings from single neurones in brain slices. Morphological properties and anatomical location of each impaled neurone were characterized by intracellular staining with biocytin. The present paper considers the properties of electrically-evoked and spontaneous postsynaptic potentials impinging on periaqueductal gray neurones, and the actions of opioids on postsynaptic potentials in neurones which were not directly hyperpolarized by opioids. The preceding paper considers neurones which were hyperpolarized by opioids. 2. Electrical stimulation in the vicinity of impaled neurones evoked postsynaptic potentials having fast (duration at half-maximal amplitude 37 +/- 2 ms, n = 65) and in some cases slow (duration at half-maximal amplitude 817 +/- 187 ms, n = 3) components. Amplitudes of evoked potentials were dependent on stimulus voltage, membrane potential, and were abolished during superfusion with solutions containing tetrodoxotoxin (100 nM to 1 microM, n = 5) or Co2+ (4 mM, n = 2). 3. Fast postsynaptic potentials were mediated predominantly by activation of glutamate and GABAA receptors. The GABAA-receptor antagonist, bicucuilline (30 microM), inhibited postsynaptic potentials by 44 +/- 8% (n = 14). The non-NMDA-receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM), inhibited postsynaptic potentials by 48 +/- 6% (n = 16). Combined superfusion of bicuculline (30 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM) inhibited postsynaptic potentials by 93 +/- 1% (n = 8). Additional superfusion of the NMDA-receptor antagonist, (+/-)-2-amino-5- phosphonovaleric acid (50 microM) inhibited synaptic potentials by 94 +/- 1% (n = 3).(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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