Adenosine-induced presynaptic inhibition of IPSCs and EPSCs in rat hypothalamic supraoptic nucleus neurones
The Journal of Physiology. 1999-11-01; 520(3): 815-825
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1. J Physiol. 1999 Nov 1;520 Pt 3:815-25.
Adenosine-induced presynaptic inhibition of IPSCs and EPSCs in rat hypothalamic
supraoptic nucleus neurones.
Oliet SH(1), Poulain DA.
(1)Laboratoire de Neurobiologie Morphofonctionnelle, INSERM U378, Universite
Victor Segalen – Bordeaux 2, 33077 Bordeaux, France.
J Physiol. 1999 Nov 1;520 Pt 3:629.
1. The effects of adenosine on synaptic transmission in magnocellular
neurosecretory cells were investigated using whole-cell patch-clamp recordings in
acute rat hypothalamic slices that included the supraoptic nucleus. 2. Adenosine
reversibly reduced the amplitude of evoked inhibitory (IPSCs) and excitatory
(EPSCs) postsynaptic currents in a dose-dependent manner (IC50 approximately 10
microM for both types of current). 3. Depression of IPSCs and EPSCs by adenosine
was reversed by the application of the A1 adenosine receptor antagonist
8-cyclopentyl-1, 3-dimethylxanthine (CPT; 10 microM). 4. When pairs of stimuli
were given at short intervals, adenosine inhibitory action was always less
effective on the second of the two responses than on the first, resulting in an
increased paired-pulse facilitation and suggesting a presynaptic site of action.
This observation was confirmed by analysis of spontaneous miniature synaptic
currents whose frequency, but not amplitude or kinetics, was reversibly reduced
by 100 microM adenosine. 5. CPT had no effect on synaptic responses evoked at a
low frequency of stimulation (0.05-0.5 Hz), indicating the absence of tonic
activation of A1 receptors under these recording conditions. However, CPT
inhibited a time-dependent depression of both IPSCs and EPSCs induced during a 1
Hz train of stimuli. 6. Taken together, these results suggest that adenosine can
be released within the supraoptic nucleus at a concentration sufficient to
inhibit the release of GABA and glutamate via the activation of presynaptic A1
receptors. By its inhibitory feedback action on the major afferent inputs to
oxytocin and vasopressin neurones, adenosine could optimally adjust electrical
and secretory activities of hypothalamic magnocellular neurones.
PMID: 10545146 [Indexed for MEDLINE]