Distinct target cell-dependent forms of short-term plasticity of the central visceral afferent synapses of the rat

Abstract

Background The visceral afferents from various cervico-abdominal sensory receptors project to the dorsal vagal complex (DVC), which is composed of the nucleus of the solitary tract (NTS), the area postrema and the dorsal motor nucleus of the vagus nerve (DMX), via the vagus and glossopharyngeal nerves and then the solitary tract (TS) in the brainstem. While the excitatory transmission at the TS-NTS synapses shows strong frequency-dependent suppression in response to repeated stimulation of the afferents, the frequency dependence and short-term plasticity at the TS-DMX synapses, which also transmit monosynaptic information from the visceral afferents to the DVC neurons, remain largely unknown. Results Recording of the EPSCs activated by paired or repeated TS stimulation in the brainstem slices of rats revealed that, unlike NTS neurons whose paired-pulse ratio (PPR) is consistently below 0.6, the distribution of the PPR of DMX neurons shows bimodal peaks that are composed of type I (PPR, 0.6-1.5; 53% of 120 neurons recorded) and type II (PPR, < 0.6; 47%) neurons. Some of the type I DMX neurons showed paired-pulse potentiation. The distinction of these two types depended on the presynaptic release probability and the projection target of the postsynaptic cells; the distinction was not dependent on the location or soma size of the cell, intensity or site of the stimulation, the latency, standard deviation of latency or the quantal size. Repeated stimulation at 20 Hz resulted in gradual and potent decreases in EPSC amplitude in the NTS and type II DMX neurons, whereas type I DMX neurons displayed only slight decreases, which indicates that the DMX neurons of this type could be continuously activated by repeated firing of primary afferent fibers at a high (~10 Hz) frequency. Conclusions These two general types of short-term plasticity might contribute to the differential activation of distinct vago-vagal reflex circuits, depending on the firing frequency and type of visceral afferents.

Perovskite neural trees

“…7 and is an inherent feature of our proton migration-driven devices. Natural synapses also preserve the ability to respond to larger stimulus [14][15][16] . Similarly here, new branches can be generated by further increasing the pulse width (blue and green curve in Fig.…”

“…6. f By applying consecutive positive or negative pulses, tree structure comprising different resistance states can be generated, with characteristics similar to synaptic behavior in the central nervous system 12,[14][15][16] . The same colored data points correspond to a fixed input that is applied to the device.…”

“…During a sequence of constant stimulus, the synaptic strength is modulated so that the weight of the synapse approaches self-limiting characteristics and maintains stability of the neural circuits 12,13 . At the same time, synapses preserve their capability to respond to a new stimulus [14][15][16] . Memory can be considered to be organized in a hierarchical way that can be represented in a tree structure 17,18 .…”

Role of Capsaicin-Sensitive C-Fiber Afferents in Neuropathic Pain-Induced Synaptic Potentiation in the Nociceptive Amygdala

“…To elucidate the mechanisms underlying the lack of LPB-CeC synaptic potentiation in the capsaicin-treated SNL rats, we analyzed the responses to the single-fiber minimal stimulation protocol in the SNL rats with and without capsaicin-treatment. For this purpose, we used theta pipette electrodes because they enabled passing currents within a highly limited area (~1 μm in diameter), thus activating a very limited number (one or a few) of afferent fibers [ 25 ]. Figure 4 A shows superimposed responses of a right CeC neuron in capsaicin-treated SNL rats to consecutively delivered theta-pipette electrode stimulation.…”

“…The stimulation intensity was first set at a moderate value and gradually decreased while the evoked EPSCs were observed. Then, the sfEPSC was identified in an "all-or-none" manner by the appearance of EPSCs with a similar waveform and latency at a consistent probability in response to a fixed stimulation intensity [ 25 ].…”