ATP‐induced sympathoexcitation involves purinergic and glutamatergic mechanisms in the RVLM‐projecting PVN neurons

Abstract

We have shown that ATP applied into the PVN induces a dose‐dependent increase in the lumbar sympathetic nerve activity (LSNA), such effect attenuated by the antagonism of P2 and/or ionotropic glutamate receptors within the PVN. In this study we aimed to evaluate whether the sympathoexcitatory responses elicited by purinergic activation within the PVN would involve the release of ATP and/or glutamate at the RVLM level. Recordings of LSNA were monitored decorticated and arterially perfused rat preparation. Three‐barrelled glass pipettes were filled with ATP (2.5 nmol), PPADS (0.5 nmol) and kynurenic acid (KYN, 10 nmol) for injection into the PVN and/or into the RVLM. Unilateral microinjection of ATP into the PVN induced an increase in the LSNA (control 100%), which was significantly attenuated 5 min after ipsilateral injection of KYN into the RVLM (59±7%, n=6, p<0.05), with recovery to control level 30 min later (100±15%). ATP‐induced sympathoexcitation in the PVN was also significantly attenuated 10 min after ipsilateral injection of PPADS within the RVLM (65±9%, n=9, p<0.05) with recovery 30 min later (98±14%). Our data suggests that P2 and glutamatergic receptors in the RLVM participate of the ATP‐induced sympathoexcitation into the PVN and this purino‐glutamatergic neurotransmission in the hypothalamic‐brainstem circuitry in a physiological context awaits further investigation. Sponsored by CAPES, CNPq, FAPESP.