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Central endocannabinoid modulation of baroreflex‐evoked sympathoinhibition in spontaneously hypertensive rats
Author(s) -
Brozoski Daniel T.,
Dean Caron,
Hopp Francis A.,
Seagard Jeanne L.
Publication year - 2008
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.22.1_supplement.1171.10
Subject(s) - baroreflex , microinjection , endocannabinoid system , endocrinology , medicine , baroreceptor , neurotransmission , agonist , gabaergic , phenylephrine , chemistry , receptor , blood pressure , heart rate
GABAergic neurotransmission has been reported to be greater in the spontaneously hypertensive rat (SHR) as compared to normotensive Wistar Kyoto (WKY) and Sprague Dawley (SD) rats. Previously, we have shown that endocannabinoids prolong baroreflex inhibition of renal sympathetic nerve activity (RSNA) via modulation of GABAergic neurotransmission in the nucleus tractus solitarius (NTS). Thus we proposed that endocannabinoids could prolong baroreflex‐induced sympathoinhibition more in SHRs than in normotensive rats. This study characterized the physiological role of endogenously released endocannabinoids in the NTS on baroreflex control of RSNA evoked by pressor responses (phenylephrine bolus) or direct stimulation of the baroreflex (NTS microinjection of the excitatory amino acid agonist d,l‐homocysteic acid). Baroreflex responses were compared before and after a microinjection of an indirect cannabinoid 1 receptor agonist, AM404, into the barosensitive region of the NTS of adult male SD rats, WKY rats, and SHRs. AM404 microinjections into the NTS were found to significantly prolong baroreflex‐induced sympathoinhibition in SD and WKY rats, but had an insignificant effect in SHRs. This observation suggests that endocannabinoid modulation of GABAergic transmission in SHRs is reduced and could contribute to elevated sympathetic tone characteristic of this model. VA Medical Research Funds.