Cannabinoid CB₁ receptor-mediated inhibition of noradrenaline release in guinea-pig vessels, but not in rat and mouse aorta

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• 作者：T. Schulthei脽 ; K. Flau ; M. Kathmann ; M. G枚thert and E. Schlicker
• 关键词：Rimonabant ; WIN 55 ; 212 ; 2 ; Cannabinoid CB1 receptor ; Presynaptic receptor ; Guinea ; pig aorta ; Rat aorta ; Noradrenaline release ; Prostaglandin E2
• 刊名：Naunyn-Schmiedeberg's Archives of Pharmacology
• 出版时间：August 2005
• 出版年：2005
• 期刊代码：190_0028-1298
• 类别：bio
• 卷：372
• 期：2
• 页码：139-146
• 数据来源：sp

摘要

Cannabinoids exert complex effects on blood pressure related to their interference with cardiovascular centres in the central nervous system and to their direct influence on vascular muscle, vascular endothelium and heart. In view of the relative lack of information on the occurrence of CB₁ receptors on the vascular postganglionic sympathetic nerve fibres, the aim of the present study was to examine whether cannabinoid receptor ligands affect the electrically evoked tritium overflow in superfused vessels (tissue pieces) from the guinea-pig, the rat and the mouse preincubated with 3H-noradrenaline. The cannabinoid receptor agonist WIN 55,212-2 (R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]-pyrrolo[1,2,3-de]1,4-benzoxazinyl](1-naphthalenyl) methanone) inhibited the evoked tritium overflow in the guinea-pig aorta, but not in that of the rat or mouse. The concentration–response curve of WIN 55,212-2 was shifted to the right by the CB₁ receptor antagonist rimonabant, yielding an apparent pA₂ value of 7.9. The most pronounced (near-maximum) inhibition obtained at the highest WIN 55,212-2 concentration applied (3.2 μM) amounted to 40%. WIN 55,212-2 also inhibited the evoked overflow in guinea-pig pulmonary artery, basilar artery and portal vein, again in a manner sensitive to antagonism by rimonabant. The latter did not affect the evoked overflow by itself in the four vessels, but did increase the electrically evoked tritium overflow from superfused guinea-pig hippocampal slices preincubated with 3H-choline and from superfused guinea-pig retina discs preincubated with 3H-noradrenaline (labelling dopaminergic cells in this tissue). The inhibitory effect of 3.2 μM WIN 55,212-2 on the evoked overflow from the guineapig aorta was comparable in size to that obtained with agonists at the histamine H₃, κ opioid (KOP) and ORL₁ (NOP) receptor (1 or 10 μM, producing the respective near-maximum effects) whereas prostaglandin E₂ 1 μM caused a higher near-maximum inhibition of 70%. Prostaglandin E₂ also induced an inhibition by 65 and 80%in the rat and mouse aorta respectively, indicating that the present conditions are basically suitable for detecting presynaptic receptor-mediated inhibition of noradrenaline release. The results show that the postganglionic sympathetic nerve fibres in the guineapig aorta, but not in the rat or mouse aorta, are endowed with presynaptic inhibitory cannabinoid CB₁ receptors; such receptors also occur in guineapig pulmonary artery, basilar artery and portal vein. These CB₁ receptors are not subject to an endogenous tone and the extent of inhibition obtainable via these receptors is within the same range as that of several other presynaptic heteroreceptors, but markedly lower than that obtainable via receptors for prostaglandin E₂.