Yamamoto K, Lalley PM, Mifflin SW.
Am J Physiol Regul Integr Comp Physiol. 2014 Dec
17:ajpregu.00381.2014
In this
paper, they built on previous work that showed that the effect of acute
intermittent hypoxia (AIH) on long term facilitation (LTF) of phrenic nerve
activity (PNA) and renal sympathetic nerve activity (RSNA) seems to be routed
through the nucleus tractus solitarius (NTS), and that you could induce the same effect by electrical
stimulation of the carotid sinus, even without hypoxia. They took this idea a
step further by causing expression of channelrhodopsin in the caudal NTS, via a
virus that would cause preferential expression in glutamatergic neurons.
Once
they had this system in operation, they compared the effects of AIH with the
effects of acute intermittent optogenetic stimulation (AIO) on RSNA and PNA
immediately after, and 60 minutes after periods of stimuli. They found that AIO
in the caudal NTS produces a similar, but weaker, response to that seen after
AIH (RSNA and PNA increased by 60% and 100% after AIO, but by 80 and 130% after
AIH). They also found that, while both
stimuli increased the power spectral density of RSNA and PNA at their own
primary frequencies, neither stimulus was able to increase synchronization of
PNA with RSNA. -DH
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