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Intravenous (i.v.) injection of the endocannabinoid anandamide induces triphasic cardiovascular responses, including a pressor effect mediated via unknown central and peripheral mechanism(s). The aim of the present study was to determine the central mechanism(s) responsible for the pressor response to anandamide. For this purpose, the influence of antagonists at thromboxane A(2) TP (sulotroban, daltroban, SQ 29548), NMDA (MK-801) and beta(2)-adrenergic receptors (ICI 118551) on the pressor effect induced by i.v. and intracerebroventricularly (i.c.v.) administered anandamide was examined in urethane-anaesthetized rats. Anandamide (1.5-3 micromol/kg, i.v.) or its stable analogue methanandamide (0.75 micromol/kg, i.v.) increased blood pressure by 25%. Anandamide (0.03 mumol per animal i.c.v.) caused a pure pressor effect (by 20%) but only in the presence of antagonists of CB(1) and TRPV1 receptors. The effects of cannabinoids (i.v. or i.c.v.) were diminished by i.v. daltroban, sulotroban (10 mumol/kg each), and/or SQ 29548 (1 mumol/kg). The effect of anandamide i.v. was reduced by SQ 29548 (0.02 mumol per animal i.c.v.) and by the thromboxane A(2) synthesis inhibitor furegrelate i.c.v. (1.8 micromol per animal). ICI 118551, MK-801 (1 micromol/kg i.v. each), and bilateral adrenalectomy diminished the effect of anandamide i.c.v. Sulotroban (i.v.) failed to affect the response to anandamide (i.v.) in pithed rats, and anandamide and methanandamide did not bind to TP receptors in rat platelets. The present study suggests that central beta(2)-adrenergic, NMDA and thromboxane A(2) receptors are involved in the anandamide-induced adrenal secretion of catecholamines and their pressor effect in urethane-anaesthetized rats.

Background and purpose: We examined whether cannabinoid CB1 and histamine H3 receptors resemble α2-adrenoceptors in that their presynaptically mediated cardiovascular effects are less marked in urethane- than in pentobarbitone-anaesthetized pithed rats. Experimental approach: Effects of the cannabinoid agonist CP-55,940 and the H3 receptor agonist imetit on electrically induced tachycardic and vasopressor responses, respectively, was compared in pithed rats anaesthetized with urethane or pentobarbitone. The affinity of urethane for the three receptors was measured by radioligand binding studies in rat brain cortex membranes and its potency assessed in superfused mouse tissues preincubated with 3H-noradrenaline. Key results: The neurogenic tachycardic response was less markedly inhibited by CP-55,940 in urethane- than in pentobarbitone-anaesthetized pithed rats. Imetit inhibited the neurogenic vasopressor response after pentobarbitone but not after urethane. The catecholamine-induced tachycardic and vasopressor response did not differ between rats anaesthetized with either compound. Urethane 10 mM (plasma concentration reached under anaesthesia) did not affect binding to CB1 or H3 receptors and α2 adrenoceptors, nor did it alter the inhibitory effect of agonists at the three receptors on electrically evoked 3H-noradrenaline release. Conclusions and implications: Urethane, but not pentobarbitone, abolished the H3 receptor-mediated vascular response in pithed rats and attenuated the CB1 receptor-mediated cardiac response much more than pentobarbitone. The weaker effects of CB1, H3 and α2 receptor agonists cannot be explained by antagonism by urethane at the three receptors in vitro. Pentobarbitone, but not urethane, is suitable as an anaesthetic for investigations of inhibitory presynaptic receptor function in pithed and anaesthetized rats.

We studied whether cannabinoid CB(1) receptors occur on the sympathetic neurones innervating the guinea-pig atrium and renal cortex. Atrial and cortical kidney pieces preincubated with [(3)H]-noradrenaline were superfused and the electrically (3 Hz)-evoked tritium overflow was examined. The evoked overflow in atrium was inhibited by the cannabinoid agonist WIN 55,212-2 maximally by 35%; its concentration-response curve was shifted to the right by the CB(1) antagonist rimonabant (pA(2) 8.3), which, by itself, did not affect the evoked overflow. The evoked overflow in the renal cortex was not altered by WIN 55,212-2. The muscarinic agonist oxotremorine and prostaglandin E(2) inhibited the evoked overflow maximally by 55 and 65% in atrium and by 80 and 55% in kidney, respectively. Furthermore, the nucleotide sequence of the guinea-pig CB(1) receptor was determined (GenBank DQ355990). The deduced amino acid sequence has a high homology to the corresponding sequence of man (98.7%) and rat or mouse (99.2%). In conclusion, presynaptic CB(1) receptors leading to inhibition of noradrenaline release occur in guinea-pig atrium but not renal cortex. The deduced amino acid sequence of the guinea-pig CB(1) receptor shows a homology of 99% to the CB(1) receptor sequence of rodents and humans.

Many new therapeutic approaches are based on gene transfection of cells. Data about dynamic interaction with cell membranes can support the selection of polymers and polyplexes regarding an optimal gene delivery reagent. A microchip/-fluidic system and an impedance-based method for monitoring the effects on individual cells after application of polymeric DNA-delivery systems is developed and evaluated. It was successfully demonstrated that the effects of polymers on the cell membrane can be monitored over time by using impedance measurements.