Physiological function of the descending projection from the insular cortex to the parabrachial nucleus revealed by optogenetics

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  • オプトジェネティックスによる島皮質から腕傍核への下行性投射における生理学的機能の解明

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<p>The parabrachial nucleus (PB) relays nociceptive information from secondary neurons to the higher brain regions including the insular cortex (IC). The descending pathway from the IC to the PB is also reported, and thus, it is likely that the IC regulates PB activities in accordance with the ascending nociceptive information processed in the PB. However, little is known about IC projections to the PB. To investigate the physiological function of the ICàPB projection, we examined the synaptic properties of these synapses by injecting AAV5-CAG-HChR2(H134R)-mCherry into the IC of ChAT-tdTomato-VGAT-Venus rats, in which GABAergic, glutamatergic, and cholinergic neurons are easily identified. One month after AAV5 injection, we recorded optogenetically induced synaptic currents by a whole-cell patch-clamp recording technique from PB neurons. The amplitude of optogenetically induced EPSCs was much larger in glutamatergic neurons in comparison to those in GABAergic neurons. These EPSCs were suppressed by carbachol, and counteracted by pirenzepine, selective effects on muscarinic M1 receptors. These results suggest that IC neurons induce facilitative effects on PB excitatory neurons, which are suppressed by acetylcholine via M1 receptors.</p>

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