Lecture 19: Viscerosensory Processing in the NTS Flashcards
What is the solitary tract?
the VIIth, VIIIth and Xth cranial nerves
What is an output of the solitary tract?
the NTS
this is where cranial viscerosensory afferents terminate
What is the path of cranial viscerosensory afferent neurons from the periphery to the brain?
periphery -> vagus nerve -> Xth cranial nerve -> solitary tract -> NTS
What does injection of tracing dyes into ganglia known to contain the cell bodies of these neurons (such as the nodose) reveal?
that their terminal fields are in the NTS
The presence of which protein suggests that they are forming synapses with NTS neurons?
synaptophysin
Where do cranial visceral sensory neurons synapse?
at second order neuron soma
What do visceral signals evoke?
glutamate release at the ST-NTS synapse
What is the process of synchronous neurotransmitter release?
membrane depolarisation -> voltage gated sodium channels -> voltage activated calcium channels -> neurotransmitter release
What is the percentage of NTS neurons that receive one, two and three inputs?
65%
20%
15%
What is the nature of the solitary tract input to NTS?
a relatively sparse excitatory network, where one primary afferent dominates the information pathway
What do cranial visceral sensory neurons input to?
dedicated second order neurons
What are characteristics of myelinated A-fibers?
active at resting blood pressure
fine-tune autonomic function
myelinated
What are characteristics of unmyelinated C-fibers?
activated at elevated blood pressure
TRPV1
What does asynchronous release extend?
the postsynaptic excitatory period
Which class of neuron expresses TRPV1 receptors?
C-fibers
Which class of neuron expressing TRPV1 exhibits asynchronous glutamate release?
C-fibers
Capsaicin inhibits the activation of second order NTS neurons as evoked by electrical activation of the solitary tract. By what mechanism does this occur?
depolarisation block in the presynaptic neuron
What are the two major evoked modes of neurotransmitter release?
synchronous and asynchronous
Where is TRPV1 expressed? What do they release?
at C-fiber cranial visceral afferents and release additional glutamate via asynchronous release
