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Trigeminal nerve ganglion stimulation‐induced neurovascular reflexes in the anaesthetized cat: Role of endothelin B receptors in carotid vasodilatation
Author(s) -
Raval Pravin,
Bingham Sharon,
Aiyar Nambi,
Elliott John D,
Hunter A Jackie,
Ohlstein Eliot H,
Parsons Andrew A
Publication year - 1999
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 - 10.1038/sj.bjp.0702306
Subject(s) - guanethidine , medicine , trigeminal ganglion , anesthesia , vascular resistance , vasodilation , stimulation , endocrinology , hemodynamics , anatomy , biology , sensory system , neuroscience
The effects of intravenous administration of endothelin (ET) receptor antagonists SB‐209670 (0.001–10.0 mg kg −1 ), SB‐217242, SB‐234551 (0.01–10.0 mg kg −1 ) and BQ‐788 (0.001–1.0 mg kg −1 ) were investigated on trigeminal nerve ganglion stimulation‐induced neurovascular reflexes in the carotid vasculature of the anaesthetized cat. Comparisons were made with sumatriptan (0.003–3.0 mg kg −1 ) and α‐CGRP 8–37 (0.001–0.1 mg kg −1 ). Trigeminal nerve ganglion stimulation produced frequency related increases in carotid blood flow, reductions in carotid vascular resistance and non‐frequency related increases in blood pressure. Guanethidine (3 mg kg −1 , i.v.) blocked trigeminal nerve ganglion‐induced increases in blood pressure but had no effect on changes in carotid flow or resistance. Maximal reductions in carotid vascular resistance was observed at 10 Hz, and this frequency was selected to investigate the effects of drugs on trigeminal nerve ganglion stimulation‐induced responses in guanethidine treated cats. Saline, α‐CGRP 8–37 SB‐209670 and BQ‐788 had little or no effect on resting haemodynamic parameters. SB‐217242 (10 mg kg −1 , n =3) produced a 56% reduction in arterial blood pressure whereas SB‐233451 (10 mg kg −1 , n =3) produced a 30% reduction in carotid vascular resistance. Sumatriptan produced dose‐related reductions in resting carotid flow and increases (max. 104% at 0.3 mg kg −1 , n =5) in vascular resistance. SB‐209670 ( n =6–7), SB‐217242 ( n =3) and BQ‐788 ( n =3) produced inhibition of trigeminal nerve ganglion stimulation‐induced reductions in carotid vascular resistance. Saline, SB‐234551, α‐CGRP 8–37 and sumatriptan had no effect. These data demonstrate ET B receptor blockade attenuates the vasodilator effects of trigeminal nerve ganglion stimulation in the carotid vascular bed of guanethidine pretreated anaesthetized cats.British Journal of Pharmacology (1999) 126 , 485–493; doi: 10.1038/sj.bjp.0702306