No abstract

The substantia gelatinosa (SG, lamina II of spinal cord gray matter) is pivotal for modulating nociceptive information from the peripheral to the central. γ-Aminobutyric acid type B receptors (GABA B Rs), the metabotropic GABA receptor subtype, are widely expressed in pre-and postsynaptic structures of the SG neurons. Activation of GABA B Rs by exogeneous agonists induces both pre-and postsynaptic inhibitions. However, the actions of endogenous GABA via presynaptic GABA B Rs on glutamatergic synapses, and the postsynaptic GABA B Rs interaction with glutamate, remain elusive. In the present study, rst, using in vitro whole cell recordings and taking minimal stimulation strategies, we found that in rat spinal cord glutamatergic synapses, blockade of presynaptic GABA B Rs switched "silent" synapses into active ones and increased the probability of glutamate release onto SG neurons; increasing ambient GABA concentration mimicked GABA B Rs activation on glutamatergic terminals. Next, using holographic photostimulation to uncage glutamate on postsynaptic SG neurons, we found that postsynaptic GABA B Rs modi ed glutamate-induced postsynaptic potentials. Taken together, our data identify that endogenous GABA heterosynaptically constrains glutamate release via persistently activating presynaptic GABA B Rs; and postsynaptically, GABA B Rs modulate glutamate responses. The results give new clues for endogenous GABA in modulating nociception circuit in spinal dorsal horn and shed fresh light on postsynaptic interaction of glutamate and GABA.

No abstract

No abstract

The substantia gelatinosa (SG, lamina II of spinal cord gray matter) is pivotal for modulating nociceptive information from the peripheral to the central. γ-Aminobutyric acid type B receptors (GABABRs), the metabotropic GABA receptor subtype, are widely expressed in pre- and postsynaptic structures of the SG neurons. Activation of GABABRs by exogeneous agonists induces both pre- and postsynaptic inhibitions. However, the actions of endogenous GABA via presynaptic GABABRs on glutamatergic synapses, and the postsynaptic GABABRs interaction with glutamate, remain elusive. In the present study, first, using in vitro whole cell recordings and taking minimal stimulation strategies, we found that in rat spinal cord glutamatergic synapses, blockade of presynaptic GABABRs switched “silent” synapses into active ones and increased the probability of glutamate release onto SG neurons; increasing ambient GABA concentration mimicked GABABRs activation on glutamatergic terminals. Next, using holographic photostimulation to uncage glutamate on postsynaptic SG neurons, we found that postsynaptic GABABRs modified glutamate-induced postsynaptic potentials. Taken together, our data identify that endogenous GABA heterosynaptically constrains glutamate release via persistently activating presynaptic GABABRs; and postsynaptically, GABABRs modulate glutamate responses. The results give new clues for endogenous GABA in modulating nociception circuit in spinal dorsal horn and shed fresh light on postsynaptic interaction of glutamate and GABA.