Sympathomotor activation by midbrain locomotor neurons is mediated through glutamate release in the rostral ventrolateral medulla

Abstract

Our pilot data showed that a portion of neuronal cells in the mecencephalic locomotor region (MLR) sends axonal projections to the rostral ventrolateral medulla (RVLM) (MLR‐RVLM pathway), being capable of eliciting sympathomotor activation in rats. Here, we examined the effect of ionotropic glutamate receptor blockade in rat RVLM on sympathomotor activation by the MLR‐RVLM pathway. Male rats received microinjections bilaterally in the RVLM with a retrograde adeno‐associated virus that encoded a channelrhodopsin with green fluorescence protein. Under anesthesia, 473 nm wavelength laser illumination of the MLR after administration in the RVLM with a cocktail of AP5 and CNQX, NMDA and AMPA glutamate receptor blockers, respectively, elicited 29% less (P < 0.05) renal sympathoexcitation than that after saline administration. Likewise, under decerebration without anesthesia, ventral root fiber excitation in response to MLR photostimulation seen after saline administration in the RVLM was suppressed to a 35% extent (P < 0.05) by preliminarily administration of the glutamate receptor blockers. These observations suggest that glutamatergic neurons in the MLR‐RVLM pathway function in generating central command function.Support or Funding InformationSupported by JSPS KAKENHI 18H03151 (S. Koba).