1 This study was directed at exploring the structure-activity relationship for anandamide and certain of its analogues at the rat VR1 receptor in transfected cells and at investigating the relative extent to which anandamide interacts with CB 1 and vanilloid receptors in the mouse vas deferens. 2 pK i values for displacement of [ 3 H]-resiniferatoxin from membranes of rVR1 transfected CHO cells were signi®cantly less for anandamide (5.78) than for its structural analogues N-(4-hydroxyphenyl)-arachidonylamide (AM404; 6.18) and N-(3-methoxy-4-hydroxy)benzyl-arachidonylamide (arvanil; 6.77). 3 pEC 50 values for stimulating 45 Ca2+ uptake into rVR1 transfected CHO cells were signi®cantly less for anandamide (5.80) than for AM404 (6.32) or arvanil (9.29). Arvanil was also signi®cantly more potent than capsaicin (pEC 50 =7.37), a compound with the same substituted benzyl polar head group as arvanil. 4 In the mouse vas deferens, resiniferatoxin was 218 times more potent than capsaicin as an inhibitor of electrically-evoked contractions. Both drugs were antagonized to a similar extent by capsazepine (pK B =6.93 and 7.18 respectively) but were not antagonized by SR141716A (1 mM). Anandamide was less susceptible than capsaicin to antagonism by capsazepine (pK B =6.02) and less susceptible to antagonism by SR141716A (pK B =8.66) than methanandamide (pK B =9.56). WIN55212 was antagonized by SR141716A (pK B =9.02) but not by capsazepine (10 mM). 5 In conclusion, anandamide and certain of its analogues have anity and ecacy at the rat VR1 receptor. In the mouse vas deferens, which seems to express vanilloid and CB 1 receptors, both receptor types appear to contribute to anandamide-induced inhibition of evoked contractions.

Advanced glycation and lipoxidation end products (AGEs/ALEs) have been implicated in the pathogenesis of the major microvascular complications of diabetes mellitus: nephropathy, neuropathy, and retinopathy. This article reviews the evidence regarding the peripheral nerve and its vascular supply. Most investigations done to assess the role of AGEs/ALEs in animal models of diabetic neuropathy have used aminoguanidine as a prototypic inhibitor. Preventive or intervention experiments have shown treatment benefits for motor and sensory nerve conduction velocity, autonomic nitrergic neurotransmission, nerve morphometry, and nerve blood flow. The latter depends on improvements in nitric oxide-mediated endothelium-dependent vasodilation and is responsible for conduction velocity improvements. A mechanistic interpretation of aminoguanidine's action in terms of AGE/ALE inhibition is made problematic by the relative lack of specificity. However, other unrelated compounds, such as pyridoxamine and pyridoxamine analogues, have recently been shown to have beneficial effects similar to aminoguanidine, as well as to improve pain-related measures of thermal hyperalgesia and tactile allodynia. These data also stress the importance of redox metal ion-catalyzed AGE/ALE formation. A further approach is to decrease substrate availability by reducing the elevated levels of hexose and triose phosphates found in diabetes. Benfotiamine is a transketolase activator that directs these substrates to the pentose phosphate pathway, thus reducing tissue AGEs. A similar spectrum of improvements in nerve and vascular function were noted when using benfotiamine in diabetic rats. Taken together, the data provide strong support for an important role for AGEs/ALEs in the etiology of diabetic neuropathy.

We have extended previous investigations of four analogues of Δ8‐tetrahydrocannabinol (Δ8‐THC): 6′‐azidohex‐2′‐yne‐Δ8‐THC (O‐1184), 6′‐azidohex‐cis‐2′‐ene‐Δ8‐THC (O‐1238) and octyl‐2′‐yne‐Δ8‐THC (O‐584) and its 1‐deoxy‐analogue (O‐1315). O‐1184, O‐1238 and O‐584 displaced [3H]‐CP55940 from specific binding sites on Chinese hamster ovary (CHO) cell membranes expressing CB1 or CB2 cannabinoid receptors, with pKi values of 8.28 to 8.45 (CB1) and 8.03 to 8.13 (CB2). The pKi values of O‐1315 were significantly less, 7.63 (CB1) and 7.01 (CB2). All the analogues inhibited forskolin‐stimulated cyclic AMP production by CB1‐transfected CHO cells (pEC50=9.16 to 9.72). Only O‐1238 behaved as a full agonist in this cell line. In mouse vasa deferentia, O‐1238 inhibited electrically‐evoked contractions (pEC50=10.18 and Emax=70.5%). Corresponding values for O‐1184 were 9.08 and 21.1% respectively. At 1 nM, O‐1184 produced surmountable antagonism of the cannabinoid receptor agonist, CP55940. However, at 0.1 nM, O‐1184 did not attenuate CP55940‐induced inhibition of cyclic AMP production by CB1‐transfected CHO cells. In CB2‐transfected CHO cells, cyclic AMP production was inhibited by CP55940 (pEC50=8.59), enhanced by O‐1184 and O‐584 (pEC50=8.20 and 6.86 respectively) and not significantly affected by O‐1238 or O‐1315. At 100 nM, O‐1184 and O‐1238 produced surmountable antagonism of CP55940 in CB2 cells, decreasing the pEC50 of CP55940 from 8.61 to 7.42 (O‐1184) or from 8.54 to 7.44 (O‐1238). These data support the hypothesis that increasing the degree of unsaturation of the aliphatic side‐chain of Δ8‐THC analogues has little effect on CB1 or CB2 receptor affinity but can reduce CB1 receptor efficacy and reverse the direction of responses elicited at CB2 receptors. British Journal of Pharmacology (1999) 128, 735–743; doi:

Hyperglycaemia in diabetes mellitus results in oxidative stress and pro-inflammatory changes which contribute to vascular complications including endothelial dysfunction and peripheral neuropathy. The aim of this study was to examine whether treatment with the dominant ingredient of clove oil, eugenol, which has antioxidant and anti-inflammatory properties, could improve diabetic vascular and nerve function in streptozotocin-induced diabetic rats. Intervention treatment was given for 2 weeks following 6 weeks of untreated diabetes. Dose-ranging studies on diabetic deficits in sciatic nerve motor and saphenous nerve sensory nerve conduction velocities gave ED50 values of 28 mg/kg and 9 mg/kg, respectively, conduction velocity being within the non-diabetic range at a dose of 200 mg/kg. Sciatic nerve endoneurial blood flow was 49% reduced by diabetes and this was completely corrected by 200 mg/kg eugenol treatment. Gastric fundus maximum nitrergic nerve-mediated relaxation was 44% reduced by diabetes; eugenol corrected this deficit by 69%. For renal artery rings, maximum endothelium-dependent relaxation to acetylcholine was 51% reduced by diabetes; eugenol corrected this deficit by 60%, with improvements in both nitric oxide and endothelium-derived hyperpolarising factor (EDHF)-mediated vasorelaxation components. Diabetes increased renal artery sensitivity to phenylephrine-mediated contraction, however, this was unaffected by eugenol treatment. Thus, aspects of both vascular and neural complications in experimental diabetes are improved by eugenol, which could have potential therapeutic implications for diabetic neuropathy and vasculopathy.