Why the study?
Vagal sensory inputs alter breathing via pontomedullary circuits, but the localized effects of modulating lateral parabrachial nucleus activity on vagally evoked breathing patterns remained to be investigated.
The lateral parabrachial nucleus plays a localized role in regulating vagally-evoked respiratory reflexes such as tachypnoea and apnoea in mice.
LPB modulation alters vagally-evoked breathing in mice; hypothesis-generating for human brainstem respiratory control.
Vagal sensory inputs to the brainstem can alter breathing through the modulation of pontomedullary respiratory circuits. In this study, we set out to investigate the localised effects of modulating lateral parabrachial nucleus (LPB) activity on vagally-evoked changes in breathing pattern. In isoflurane-anaesthetised and instrumented mice, electrical stimulation of the vagus nerve (eVNS) produced stimulation frequency-dependent changes in diaphragm electromyograph (dEMG) activity with an evoked tachypnoea and apnoea at low and high stimulation frequencies, respectively. Muscimol microinjections into the LPB significantly attenuated eVNS-evoked respiratory rate responses. Notably, muscimol injections reaching the caudal LPB, previously unrecognised for respiratory modulation, potently modulated eVNS-evoked apnoea, whilst muscimol injections reaching the intermediate LPB selectively modulated the eVNS-evoked tachypnoea. The effects of muscimol on eVNS-evoked breathing rate changes occurred without altering basal eupneic breathing. These results highlight novel roles for the LPB in regulating vagally-evoked respiratory reflexes.
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Behrens et al. (2023) studied this question.
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