Figure 3
From: CB1 Receptor Signaling in the Brain: Extracting Specificity from Ubiquity
CB1-mediated effects, release probability, and presynaptic activity on postsynaptic firing. (a) Schematic depiction of a GABA synapse (blue) that has a high initial release probability. With rapid, repeated activation of the presynaptic neuron, GABA release decreases. (b) Blue traces show the spike patterns in the presynaptic neuron and the putative synaptic response immediately below in a condition when CB1 receptors are not recruited. In orange, the activity of postsynaptic neuron and the effect of the inhibitory event. Note that a single presynaptic action potential is sufficient to elicit a pause in firing of the postsynaptic neuron. A burst of presynaptic action potentials elicits a pause that is marginally longer, but rapid synaptic depression allows postsynaptic firing to resume quickly. (c) When CB1 receptors are recruited, a single action potential evokes no release and consequently, postsynaptic firing is unaffected. A burst of presynaptic action potentials, however, results in synaptic facilitation and a prolonged pause in postsynaptic firing. (d) Schematic depiction of a GABA synapse (green) that has a low initial release probability. With rapid, repeated activation of the presynaptic neuron, GABA release increases. (e) Green traces show the spike patterns in the presynaptic neuron and the putative synaptic response immediately below in a condition when CB1 receptors are not recruited. In orange, the activity of postsynaptic neuron and the effect of the inhibitory event. Note that a single presynaptic action potential has no effect on firing of the postsynaptic neuron. A burst of presynaptic action potentials results in synaptic currents that facilitate and cause a delayed pause in firing of the postsynaptic neuron. (f) When CB1 receptors are recruited, a single action potential still evokes no release and again, postsynaptic firing is unaffected. A burst of presynaptic action potentials, however, results in very profound synaptic facilitation and a prolonged pause in postsynaptic firing.
