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Sympathoinhibitory effects of rilmenidine may be mediated by sites located below the brainstem
Author(s) -
Sannajust Frédéric,
Barrès Christian,
KoenigBérard Elisabeth,
Sassard Jean
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb09015.x
Subject(s) - rilmenidine , medicine , blood pressure , anesthesia , brainstem , sympathetic nervous system , spinal cord , heart rate , baroreflex , agonist , receptor , psychiatry
1 To determine the site of action of rilmenidine, we examined its effects on arterial blood pressure (BP), heart rate (HR) and postganglionic renal sympathetic nerve activity (RSNA) after intracerebroventricular (i.c.v.) administration (300 μg kg −1 ), in groups (all n = 6) of conscious and freely moving, pentobarbitone‐anaesthetized and pentobarbitone‐anaesthetized and spinally transected, fifteen week‐old male spontaneously hypertensive rats (SHRs). 2 In conscious SHRs, which exhibited a low sympathetic nerve activity (RSNA: 3.4 ± 0.9 μV), rilmenidine was inactive on systolic BP (SBP), diastolic BP (DBP), HR and RSNA. 3 In intact pentobarbitone‐anaesthetized SHRs, which exhibited an elevated sympathetic nerve activity (RSNA: 10.6 ± 0.9 μV), rilmenidine exerted potent antihypertensive (ΔSBP: −37 ± 4%; ΔDBP: −43 ± 6%), bradycardic (ΔHR: −32 ± 3%) and sympathoinhibitory (ΔRSNA: −68 ± 9%) activities. 4 In pentobarbitone‐anaesthetized SHRs with cervical spinal cord transection, BP was markedly decreased and sympathetic nerve activity (RSNA: 10.3 ± 3.1 μV) returned to the level observed in conscious SHRs (RSNA: 3.6 ± 0.5 μV). In these conditions, rilmenidine remained sympathoinhibitory (ARSNA: −74 ± 5%). 5 In conclusion, we have shown that pentobarbitone‐anaesthesia enhances the peripheral sympathetic tone by a central action, as the spinal cord transection allows RSNA to return to normal levels and that, spinal or ganglionic structures could be a major site of the sympathoinhibitory action of rilmenidine.