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Brainstem Norepinephrine Neurons Mediate Ethanol‐Evoked Pressor Response but Not Baroreflex Dysfunction
Author(s) -
Li Guichu,
Wang Xu,
AbdelRahman Abdel A.
Publication year - 2005
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1097/01.alc.0000160083.72579.ec
Subject(s) - baroreflex , pressor response , norepinephrine , brainstem , medicine , locus coeruleus , neuroscience , cardiology , anesthesia , biology , blood pressure , heart rate , central nervous system , dopamine
Background: Ethanol elicits strain‐dependent blood pressure and baroreflex sensitivity responses in spontaneously hypertensive rats (SHRs) and Wistar‐Kyoto (WKY) rats; the mechanisms underlying these divergent effects are not clear. The authors tested the hypothesis that differential neuronal actions of ethanol may account for these strain‐dependent responses. To this end, the authors investigated the direct effects of ethanol on norepinephrine (NE)–containing neurons in the rostral ventrolateral medulla (RVLM), which modulate sympathetic neuronal activity, and on c‐Jun–expressing neurons in the nucleus tractus solitarius (NTS), whose activity is inversely correlated with baroreflex sensitivity. Methods: In a newly developed model system in conscious, freely moving rats, the effect of intra‐RVLM or intra‐NTS ethanol was investigated on neuronal NE at the microinjection site (in vivo electrochemistry), blood pressure, heart rate, spontaneous baroreflex sensitivity, and c‐Jun expression in the NTS. Results: Ethanol (1, 5, or 10 μg) microinjection into the RVLM elicited dose‐dependent increases in RVLM NE and blood pressure in SHRs but not in WKY rats. Ethanol had no effect on the activity of the NE‐containing neurons in the NTS of either strain. However, baroreflex dysfunction elicited by intra‐NTS ethanol in conscious WKY rats was associated with enhanced expression of c‐Jun in the NTS. Conclusions: (1) Ethanol activation of the NE‐containing neurons in the RVLM of SHRs contributes to the centrally mediated pressor response, (2) the NE‐containing neurons in the NTS are not involved in ethanol‐induced baroreflex dysfunction, and (3) direct activation of the c‐Jun–containing neurons in the NTS is implicated in baroreflex dysfunction elicited by ethanol in normotensive rats.