Different sub‐populations of pre‐sympathetic neurons are revelead by acute hypoxia in brainstem slices of adult rats (710.7)

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In this study we evaluated, in brainstem slices from adult rats, the effects of acute hypoxia (AH) on the firing rate of pre‐sympathetic neurons in rostral ventrolateral medulla sending projections to the intermediolateral column of spinal cord (RVLM‐IML neurons). Anesthetized male Wistar rats (PO 30) were submitted to microinjection of fluorescent retrograde tracer into the spinal cord (T3‐T5) to label the RVLM‐IML neurons. Five days later the rats were anesthetized to obtain brainstem coronal slices. The RVLM‐IML neurons were recorded using whole‐cell patch‐clamp and the firing rate was analyzed before and after perfusion of slice to AH for 2 minutes with hypoxic solution (95% N2 and 5% CO2) in the presence of synaptic blockers. After the AH protocol the viability of RVLM‐IML neurons were verified by the perfusion with normal solution (95% O2 and 5% CO2). All recorded RVLM‐IML neuronsof adult rats (n=17) presented intrinsic spontaneous firing activity. Three sub‐populations of RVLM‐IML neurons were identified after AH exposure: a) 3 neurons decreased their firing rate after AH(‐ 34,10%, p= 0,0225); b) 4 neurons increased their firing rate after AH (+ 40,86%, p= 0,0249) and c) 10 neurons were not affected by AH(± 3,54%, p= 0,5380. Hypoxia produced no changes in input resistance and resting membrane potential in these neurons. The data show that pre‐sympathetic neurons in the brainstem slices of adult rats present pacemaker activity and different sub‐populations of pre‐sympathetic neurons are revealed in response to AH.Grant Funding Source: Supported by FAPESP and CNPQ