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Sciatic nerve stimulation activates the retrotrapezoid nucleus in anesthetized rats
Roy Kanbar1, Ruth L Stornetta2, Patrice G Guyenet3
1Department of Pharmaceutical Sciences, School of Pharmacy, Lebanese American University, Byblos, Lebanon; and.
Journal of Neurophysiology
|August 12, 2016
Summary
Somatic afferent stimulation excites retrotrapezoid nucleus (RTN) neurons, which control breathing. This response enhances RTN neuron firing probability without changing their CO2 sensitivity, potentially contributing to hyperpnea during exercise or hyperthermia.
Area of Science:
- Neuroscience
- Respiratory Physiology
Background:
- The retrotrapezoid nucleus (RTN) is crucial for maintaining automatic breathing.
- RTN neurons possess chemoreceptor properties but receive synaptic inputs of unclear function.
- Presympathetic neurons, adjacent to RTN neurons, are known to respond to somatic afferent stimulation.
Purpose of the Study:
- To investigate whether RTN neurons are excited by somatic afferent stimulation, similar to neighboring presympathetic neurons.
- To determine the functional impact of somatic afferent stimulation on RTN neuron activity and its interaction with chemosensory drive.
Main Methods:
- Experiments were conducted in anesthetized, ventilated rats.
- Extracellular recordings of RTN and presympathetic neurons were performed.
- Sciatic nerve stimulation (SNstim) was applied, and its effects on neuronal firing and phrenic nerve discharge (PND) were analyzed under varying end-expiratory CO2 (eeCO2) levels.
Main Results:
- Sciatic nerve stimulation (SNstim) evoked a biphasic excitation in a majority of RTN neurons and a monophasic excitation in the remainder.
- RTN neuron responses to SNstim were weaker at low eeCO2 and independent of PND entrainment.
- SNstim shifted the relationship between RTN firing rate and eeCO2 upward, increasing firing probability without altering CO2 sensitivity.
Conclusions:
- Somatic afferent stimulation increases the firing probability of RTN neurons.
- This pathway does not alter the intrinsic CO2 response of RTN neurons.
- The findings suggest a role for this pathway in mediating hyperpnea associated with nociception, exercise, or hyperthermia.
