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Pattern of sympathetic vasomotor activity induced by GABAergic inhibition in the brain and spinal cord
Author(s) -
Campos Ruy R.,
Milanez Maycon I.,
Silva Adilson M.,
Perry Juliana C.,
Faber Jean,
Nishi Erika E.,
Bergamaschi Cassia
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.05164
Subject(s) - bicuculline , rostral ventrolateral medulla , gabaergic , medicine , vasomotor , splanchnic , microinjection , endocrinology , gaba receptor antagonist , spinal cord , inhibitory postsynaptic potential , central nervous system , gabaa receptor , medulla oblongata , hemodynamics , receptor , psychiatry
Background The knowledge of the central areas involved in the control of sympathetic vasomotor activity has been advanced in the last few decades. The γ‐aminobutyric acid (GABA) is the mainly inhibitory neurotransmitter in the mammal central nervous system and bicuculline, an antagonist of GABA type A receptors (GABA‐A), microinjected into the paraventricular nucleus of the hypothalamus (PVN) alters the pattern of sympathetic vasomotor activity to the renal, splanchnic and lumbar territories. However, studies are needed to clarify the role of GABAergic inputs in other central areas involved in the control of sympathetic vasomotor activity. Thus, the present work studied the cardiovascular effects evoked by GABAergic inhibition in the PVN, RVLM and the spinal cord. Methods and Results All experimental approach applied in this present study agreed to the guidelines recommended by the National Institute of Health and were approved by the Ethics in Research Committee of the Escola Paulista de Medicina – Universidade Federal de São Paulo (8724270715/15). In urethane (1.4 g/kg, iv) Wistar male anesthetized rats, Bicuculline microinjection (400 pMol in 100 nL) into the PVN and rostral ventrolateral medulla (RVLM), as well its intrathecal administration (1.6 nmol in 2 μL) evoked an increase in blood pressure, heart rate, renal and splanchnic sympathetic nerve activity (rSNA and sSNA, respectively) inducing a higher coherence of rSNA and sSNA pattern. However, some of these responses were more intense when the GABA‐A antagonism was performed into the RVLM. Conclusions Administration of bicuculline into the RVLM, PVN and SC induced a similar pattern of renal and splanchnic sympathetic vasomotor burst discharge, characterized by a low frequency (0.5 Hz) and high amplitude pattern despite different blood pressure responses. Thus, the 0.5 Hz recorded in sympathetic nerves to different targets is dependent in part of tonic GABAergic inputs in the brain (RVLM and PVN) and spinal cord. The origin of the GABAergic projections is unknown. Support or Funding Information CAPES ‐ Finance Code 001; FAPESP ‐ 18/02671‐3 and CNPq 309020/2017‐4.