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Role of brainstem adenosine A 1 receptors in the cardiovascular response to hypothalamic defence area stimulation in the anaesthetized rat
Author(s) -
Lambert J.H.,
Dashwood M.R.,
Spyer K.M.
Publication year - 1996
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.1476-5381.1996.tb15187.x
Subject(s) - stimulation , medicine , adenosine , rostral ventrolateral medulla , endocrinology , adenosine a1 receptor , brainstem , adenosine receptor , medulla oblongata , hypothalamus , chemistry , receptor , central nervous system , biology , agonist
1 The role of centrally located adenosine A 1 receptors in the cardiovascular changes associated with the hypothalamic defence response has been investigated by in vitro autoradiography and the intraventricular application of an A 1 receptor antagonist. 2 8‐Cyclopentyl‐1,3‐dipropylxanthine (DPCPX), a highly selective adenosine A 1 antagonist and its vehicle, ethanol, were administered directly into the posterior portion of the fourth ventricle of α‐chloralose anaesthetized, paralysed and artificially ventilated rats. 3 DPCPX (0.01 to 0.3 mg kg −1 ) caused a dose‐dependent decrease in the magnitude of the evoked pressor response (from −13 to −23 mmHg) elicited on hypothalamic defence area stimulation at a dose 10 fold lower than that required to produce an equivalent effect following systemic administration whilst ethanol, the vehicle, had no effect. 4 In vitro autoradiography revealed a heterogeneous distribution of adenosine A 1 binding sites in the lower brainstem of rats. Image analysis showed the ventrolateral medulla to have the highest density of A 1 receptors. Intermediate levels of binding were seen in caudal regions of the nucleus tractus solitarii and the hypoglossal nucleus. 5 These data imply that a proportion of the cardiovascular response to hypothalamic defence area stimulation are produced by the activation of adenosine A 1 receptors localized close to the surface of, or adjacent to, the fourth ventricle in the immediate vicinity of the injection site.