Characterization of synaptic transmission in the ventrolateral periaqueductal gray of rat brain slices
Section snippets
Brain slice preparations
Brain slices of 400 μm containing the midbrain PAG were dissected coronally from Wistar rats of 12–18 days age, as reported previously.12 After equilibrium, slices were transferred to a submerged chamber and perfused with artificial cerebral spinal fluid (ACSF) at 2–3 ml/min. ACSF contained (mM) NaCl 117, KCl 4.5, CaCl2 2.5, MgCl2 1.2, NaH2PO4 1.2, NaHCO3 25 and dextrose 11.4, and was oxygenated with 95% O2 plus 5% CO2.
Electrophysiological recordings
Blind patch-clamp whole-cell recording8 was conducted in the ventrolateral
Results
Experiments were performed on 60 cells. The mean resting membrane potential was −62±1 mV. Input resistance varied from 90 MΩ to 1.6 GΩ and averaged 531±37 MΩ.
Discussion
The present study demonstrates that focal stimulation within the ventrolateral PAG elicited a dominant inhibitory neurotransmission as well as an excitatory one. The inhibitory synaptic transmission is mediated by GABAA, but not GABAB, receptors. The excitatory synaptic transmission is mediated by glutamate acting on AMPA/kainate and NMDA receptors. The NMDA receptor-mediated synaptic response is characterized by an Mg2+-sensitive voltage-dependent block, like those found in other brain areas.30
Acknowledgements
This work was supported by grant NSC 89-2320-B002-076 from the National Science Council, ROC (L.C.C.).
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