Biomedical subjects

D A Kendall

Publications and source records attributed to D A Kendall.

At least 19 recordsLinked to original sources

PubMed2006

Behavioral, central monoaminergic and hypothalamo-pituitary-adrenal axis correlates of fear-conditioned analgesia in rats.

Fear-conditioned analgesia is an important survival response which is expressed upon re-exposure to a context previously paired with a noxious stimulus. The aim of the present study was to characterize further the behavioral, monoaminergic and hypothalamo-pituitary-adrenal axis alterations associated with expression of fear-conditioned analgesia. Rats which had received footshock conditioning 24 h earlier, exhibited reduced formalin-evoked nociceptive behavior upon re-exposure to the footshock chamber, compared with non-footshocked formalin-treated rats. Intra-plantar injection of formalin reduced the duration of contextually-induced freezing and 20-40 kHz ultrasound emission. Intra-plantar injection of formalin to non-footshocked, non-conditioned rats did not induce ultrasonic vocalizations. Intra-plantar injection of formalin to footshock-conditioned rats, significantly increased tissue levels of 3,4-dihydroxyphenylacetic acid and the 3,4-dihydroxyphenylacetic acid:dopamine ratio in the periaqueductal gray and reduced levels of dopamine in the thalamus, compared with saline-treated footshocked controls. Non-footshocked, non-conditioned rats were capable of mounting a robust formalin-evoked increase in plasma corticosterone levels. Moreover, plasma corticosterone levels were significantly higher in saline-treated, footshock conditioned rats compared with saline-treated non-footshocked rats and levels did not differ between saline- and formalin-treated footshock conditioned rats. Assessment of the effects of the intra-plantar injection procedure revealed an attenuation of short-term extinction of contextually-induced freezing in rats anesthetized for intra-plantar injection of saline compared with non-anesthetized, non-injected rats as well as discrete effects on monoamines, their metabolites and plasma corticosterone levels. These data extend behavioral characterization of the phenomenon of fear-conditioned analgesia and suggest that measurement of ultrasound emission may be used as an ethologically relevant index of the defense response during fear-conditioned analgesia. Ultrasonic vocalization may also be a useful behavioral output to aid separation of nociception and aversion. The data provide evidence for discrete alterations in dopaminergic activity in the periaqueductal gray and thalamus and for altered hypothalamo-pituitary-adrenal axis activity following expression of defensive behavior.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2006

Cannabinoids and PPARalpha signalling.

Cannabinoids have been shown to possess anti-inflammatory and neuroprotective properties, which were proposed to occur mainly via activation of the G-protein-coupled receptor CB(1) (cannabinoid receptor 1). Recently, certain cannabinoids have been reported to be ligands for members of the nuclear receptor transcription factor superfamily known as PPARs (peroxisome-proliferator-activated receptors). This review summarizes the evidence for cannabinoid activation of PPARs and identifies a new intracellular target for cannabinoids as therapeutic agents for neuroprotective treatment.

Animals↗

PubMed2006

Effects of inhibition of fatty acid amide hydrolase vs. the anandamide membrane transporter on TRPV1-mediated calcium responses in adult DRG neurons; the role of CB receptors.

The aim of the present study was to investigate the relationship between TRPV1 stimulation and endocannabinoid-driven CB(1) receptor-mediated inhibition of activity in adult rat dorsal root ganglion (DRG) neurons, a model of primary afferent nociceptors. Calcium-imaging studies were performed to compare the effects of the fatty acid amide hydrolase (FAAH) inhibitor URB597 (1 microm) vs. the anandamide (AEA) uptake inhibitor UCM707 (1 microm) on capsaicin (100 nm) and N-arachidonoyl dopamine (NADA; 1 microm)-evoked changes in intracellular calcium [Ca(2+)](i) in DRG neurons. The ability of the CB(1) receptor antagonist AM251 (1 microm) to modulate the effects of URB597 and UCM707 was also determined. Suprafusion of NADA and capsaicin evoked robust increases in [Ca(2+)](i) in DRG neurons (89 +/- 4% and 132 +/- 6% of the depolarizing KCl response, respectively). Co-incubation with URB597 significantly attenuated both NADA and capsaicin-evoked increases in [Ca(2+)](i) (39 +/- 3% and 79 +/- 4% of KCl response, respectively). Similarly, co-incubation with UCM707 significantly attenuated both NADA and capsaicin-evoked increases in [Ca(2+)](i) (59 +/- 7% and 72 +/- 4% of KCl response, respectively). The CB(1) receptor antagonist AM251 significantly attenuated the effects of URB597 on NADA-evoked increases in [Ca(2+)](i) but not the effects of URB597 on capsaicin-evoked increases in [Ca(2+)](i). By contrast, AM251 significantly attenuated the inhibitory effects of UCM707 on both NADA and capsaicin-evoked increases in [Ca(2+)](i.) These data suggest that transport of both NADA and capsaicin into DRG neurons and the subsequent activation of TRPV1 is partly governed by FAAH-dependent mechanisms as well as via the putative AEA membrane transporter.

Amidohydrolases↗

PubMed2005

The effects of desmethylimipramine on cyclic AMP-stimulated gene transcription in a model cell system.

The present study utilised an in vitro cell model of the cAMP signalling pathway to investigate the actions of desipramine (DMI) and other psychoactive agents on cAMP-driven gene transcription. The model comprised CHObeta2 SPAP cells; Chinese hamster ovary cells expressing human beta2 adrenoceptors and a secreted placental alkaline phosphatase (SPAP) reporter gene with multiple cAMP response elements (CREs) in its promoter region. SPAP assays showed DMI to inhibit isoprenaline or forskolin-enhanced gene transcription in a time and concentration-dependent manner (IC50=16.6+/-2.0 microM after 18 h). This effect of DMI was not dependent upon activity at the levels of the beta2 receptor, cAMP accumulation or phosphorylation of the transcription factor, cAMP response element binding protein (CREB). The inhibitory effects were maintained in the presence of DMI for at least 3 weeks and were mimicked by exposure to norfluoxetine (the major metabolite of fluoxetine; IC50=7.2+/-1.8 microM) and the neuroleptics, chlorpromazine and clozapine, all at a concentration of 10 microM. Amphetamine (10 microM, 18 h) enhanced SPAP gene transcription. Ca2+ imaging experiments ruled out an inhibitory effect of DMI on Ca2+ influx as concluded by previous studies. The results suggest a molecular target for DMI that lies downstream of CREB phosphorylation. Whether the inhibitory action of DMI is common to naturally expressed CRE-driven genes involved in adaptive responses to antidepressants in vivo remains to be determined.

Alkaline Phosphatase↗

PubMed2005

Chlorimipramine: a novel anticancer agent with a mitochondrial target.

Mitochondria have been suggested to be a potential intracellular target for cancer chemotherapy. In this report, we demonstrate the ability of the tricyclic antidepressant chlorimipramine to kill human glioma cells in vitro by a molecular mechanism resulting in an increase in caspase 3 activity following inhibition of glioma oxygen consumption. Studies with isolated rat mitochondria showed that chlorimipramine specifically inhibited mitochondrial complex III activity, which causes decreased mitochondrial membrane potential as well as mitochondrial swelling and vacuolation. The use of chlorimipramine in human as an effective, non-toxic cancer therapeutic having a strong selectivity between cancer cells and normal cells on the basis of their mitochondrial function is discussed.

Animals↗

PubMed2005

Social threat and novel cage stress-induced sustained extracellular-regulated kinase1/2 (ERK1/2) phosphorylation but differential modulation of brain-derived neurotrophic factor (BDNF) expression in the hippocampus of NMRI mice.

The extracellular signal-regulated kinase1/2 (ERK1/2) pathway has a key role in cell survival and brain plasticity, processes that are impaired following exposure to stressful situations. We have recently validated two repeated intermittent stress procedures in male NMRI mice, social threat and repeated exposure to a novel cage, which result in clear behavioral effects following 4 weeks of application. The present results demonstrate that both repeated intermittent stress procedures alter the activity of the ERK1/2 pathway in the brain, as shown by changes in phosphorylated ERK1/2 (phospho-ERK1/2) protein expression and in the expression of downstream proteins: phosphorylated cAMP response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF), in the hippocampus, the frontal cortex and the hypothalamus. The hippocampus showed greater responsiveness to stress as the two stressors increased phospho-ERK1/2 and BDNF expression under acute condition. Following repeated stress, hyperphosphorylation of ERK1/2 was associated with up-regulation of hippocampal BDNF expression in the social threat group but not in mice exposed to novel cage. This lack of a pro-survival effect of ERK1/2 with repeated novel cage exposure may constitute an early event in stress-mediated brain pathology. The sustained BDNF up-regulation in the hippocampi of mice subjected to repeated social threat could be related to rewarding aspects of aggressive interactions, suggested by our previous studies.

Analysis of Variance↗

PubMed2004

Oleamide is a selective endogenous agonist of rat and human CB1 cannabinoid receptors.

1. The ability of the endogenous fatty acid amide, cis-oleamide (ODA), to bind to and activate cannabinoid CB(1) and CB(2) receptors was investigated. 2. ODA competitively inhibited binding of the nonselective cannabinoid agonist [(3)H]CP55,940 and the selective CB(1) antagonist [(3)H]SR141716A to rat whole-brain membranes with K(i) values of 1.14 microm (0.52-2.53 microm, Hill slope=0.80, n=6) and 2.63 microm (0.62-11.20 microm, Hill slope=0.92, n=4), respectively. AEA inhibited [(3)H]CP55,940 binding in rat whole-brain membranes with a K(i) of 428 nm (346-510 nm, Hill slope=-1.33, n=3). 3. ODA competitively inhibited [(3)H]CP55,940 binding in human CB(1) (hCB(1)) cell membranes with a K(i) value of 8.13 microm (4.97-13.32 microm, n=2). In human CB(2) transfected (hCB(2)) HEK-293T cell membranes, 100 microm ODA produced only a partial (42.5+/-7%) inhibition of [(3)H]CP55,940 binding. 4. ODA stimulated [(35)S]GTPgammaS binding in a concentration-dependent manner (EC(50)=1.64 microm (0.29-9.32 microm), R(2)=0.99, n=4-9), with maximal stimulation of 188+/-9% of basal at 100 microm. AEA stimulated [(35)S]GTPgammaS binding with an EC(50) of 10.43 microm (4.45-24.42 microm, R(2)=1.00, n=3, 195+/-4% of basal at 300 microm). Trans-oleamide (trans-ODA) failed to significantly stimulate [(35)S]GTPgammaS binding at concentrations up to 100 microm. 5. ODA (10 microm)-stimulated [(35)S]GTPgammaS binding was reversed by the selective CB(1) antagonist SR141716A (IC(50)=2.11 nm (0.32-13.77 nm), R(2)=1.00, n=6). 6. The anatomical distribution of ODA-stimulated [(35)S]GTPgammaS binding in rat brain sections was indistinguishable from that of HU210. Increases of similar magnitude were observed due to both agonists in the striatum, cortex, hippocampus and cerebellum. 7. ODA (10 microm) significantly inhibited forskolin-stimulated cyclic AMP (cAMP) accumulation in mouse neuroblastoma N1E 115 cells (P=0.02, n=11). ODA-mediated inhibition was completely reversed by 1 microm SR141716A (P<0.001, n=11) and was also reversed by pretreatment with 300 ng ml(-1) pertussis toxin (P<0.001, n=6). 8. These data demonstrate that ODA is a full cannabinoid CB(1) receptor agonist. Therefore, in addition to allosteric modulation of other receptors and possible entourage effects due to fatty acid amide hydrolase inhibition, the effects of ODA may be mediated directly via the CB(1) receptor.

Animals↗

PubMed2004

Effects of coadministration of cannabinoids and morphine on nociceptive behaviour, brain monoamines and HPA axis activity in a rat model of persistent pain.

The antinociceptive effects of Delta9-tetrahydrocannabinol (Delta9-THC) have been widely described; however, its therapeutic potential may be limited by secondary effects. We investigated whether coadministration of low doses of cannabinoids or cannabinoids and morphine produced antinociception in the absence of side-effects. Effects of preadministration (i.p.) of Delta9-THC (1 or 2.5 mg/kg), cannabidiol (5 mg/kg), morphine (2 mg/kg), Delta9-THC + morphine, Delta9-THC + cannabidiol or vehicle on formalin-evoked nociceptive behaviour were studied over 60 min. Trunk blood and brains were collected 60 min after formalin injection and assayed for corticosterone and tissue levels of monoamines and metabolites, respectively. Drug effects on locomotor activity, core body temperature and grooming were assessed. Delta9-THC reduced both phases of formalin-evoked nociceptive behaviour, enhanced the formalin-evoked corticosterone response and increased the 4-hydroxy-3-methoxyphenylglycol : noradrenaline ratio in the hypothalamus. Cannabidiol alone had no effect on these indices and did not modulate the effects of Delta9-THC. Morphine reduced both phases of formalin-evoked nociceptive behaviour. Coadministration of Delta9-THC and morphine reduced the second phase of formalin-evoked nociceptive behaviour to a greater extent than either drug alone, and increased levels of thalamic 5-hydroxytryptamine. While the antinociceptive effects of Delta9-THC and morphine alone occurred at doses devoid of effects on locomotor activity, coadministration of Delta9-THC and morphine inhibited locomotor activity. In conclusion, coadministration of a low dose of morphine, but not cannabidiol, with Delta9-THC, increased antinociception and 5-hydroxytryptamine levels in the thalamus in a model of persistent nociception. Nevertheless, these enhanced antinociceptive effects were associated with increased secondary effects on locomotor activity.

Animals↗

PubMed2004

Evidence for differential modulation of conditioned aversion and fear-conditioned analgesia by CB1 receptors.

Fear-conditioned analgesia is an important survival response mediated by substrates controlling nociception and aversion. Cannabinoid(1) (CB(1)) receptors play an important role in nociception and aversion. However, their role in fear-conditioned analgesia has not been investigated. This study investigated the effects of systemic administration of the CB(1) receptor antagonist, SR141716A (1 mg/kg, i.p.), on fear-conditioned analgesia and conditioned aversion in rats. Twenty-four hours after receiving footshock, rats exhibited reduced formalin-evoked nociceptive behaviour, increased freezing and increased defecation when tested in the footshock apparatus, compared with non-footshocked formalin-injected rats. SR141716A attenuated fear-conditioned analgesia, freezing and defecation. Importantly, SR141716A had no effect on formalin-evoked nociceptive behaviour over an equivalent time period in rats not receiving footshock. SR141716A had no effect on contextually induced freezing during the first half of the test trial in rats receiving intra-plantar injection of saline. Administration of SR1417176A did, however, attenuate short-term extinction of contextually induced freezing and ultrasound emission in rats receiving intra-plantar saline, compared with vehicle-treated saline controls. These data suggest an important role for the CB(1) receptor in mediating fear-conditioned analgesia and provide evidence for differential modulation of conditioned aversive behaviour by CB(1) receptors during tonic, persistent pain.

Analgesia↗

PubMed2003

Surface engineering of living myoblasts via selective periodate oxidation.

Cell surface molecules are vital for normal cell activity. To study the functions of these molecules or manipulate cell behavior, the ability to decorate cell surfaces with bioactive molecules of our choosing is a potentially powerful technique. Here, we describe the molecular engineering of living L6 myoblast monolayers via selective periodate oxidation of sialic acid residues and the application of this surface modification in the artificial aggregation of cells. The aldehyde groups generated by this reaction were used to selectively ligate a model molecule, biotin hydrazide, to the cell surfaces. Flow cytometry analysis after staining with fluorescently conjugated avidin revealed a concentration-dependent increase in fluorescence compared to untreated cells with a maximal shift of 345.1 +/- 27.4-fold and an EC(50) of 17.4 +/- 1.1 microM. This mild oxidation reaction did not affect cell number, viability, or morphology. We then compared this chemical technique with the metabolic incorporation of reactive cell surface ketone groups using N-levulinoylmannosamine (ManLev). In this cell line, only a 22.3-fold fluorescence shift was observed compared to untreated cells when myoblasts were incubated with a high concentration of ManLev for 48 hours. Periodate oxidation was then used to modify myoblast surfaces to induce cell aggregation. Crosslinking biotinylated myoblasts, which do not spontaneously aggregate in culture, with avidin resulted in the rapid formation of millimeter-sized, multicellular structures. These data indicate that sodium periodate treatment is an effective, noncytotoxic method for the in vitro molecular engineering of living cell surfaces with the potential for cell biology and tissue engineering applications.

Aldehydes↗

PubMed2003

Differential cannabinoid-induced electrophysiological effects in rat ventral tegmentum.

Cannabinoids are known to exert mainly excitatory effects on dopaminergic cells of the ventral tegmental area (VTA). We have utilized an in vivo multiple-single unit electrophysiological approach to assess different neuronal contributions that may ultimately lead to excitation in this area. Baseline neuron recordings, using low impedance microwires, showed a variety of waveforms with a wide range of durations (0.8-3.2 ms). In the first experiment systemic injection of the potent cannabinoid agonist HU210 (100 microg/kg, i.p.) led predominantly to an increase in firing rate (approximately 214%, compared to pre-drug) in slowly firing cells with broad action potentials, possibly driven by a majority of presumed dopaminergic neurons (n = 31). However, the firing rate of some units was either unaffected (<25%, n = 9) or even decreased (approximately 67%, n = 9) following cannabinoid injection concomitantly with excitation. Apomorphine (75 microg/kg, i.p.) injected following HU210 produced a marked inhibition of both responses (approximately 76%) in 39 out of 49 cells. The second group of animals was treated with the CB(1) receptor antagonist SR141716A (1 mg/kg, i.p.), which had no effect when injected alone but prevented all HU210-evoked changes in firing rate suggesting that cannabinoid receptors mediated the observed responses (n = 39). Taken together, the present results suggest that the observed actions of cannabinoids may involve complex neurotransmitter interactions leading to differential effects on dopamine release. These heterogeneous neuronal responses are likely to underly the behavioural discrepancies reported in animal models of cannabinoid reinforcement.

Action Potentials↗

PubMed2003

Intraplantar injection of anandamide inhibits mechanically-evoked responses of spinal neurones via activation of CB2 receptors in anaesthetised rats.

Anti-nociceptive effects of the endocannabinoid anandamide are well established. Anandamide has, however, also been shown to activate pro-nociceptive vanilloid 1 (VR1) receptors present on primary afferent nociceptors. The aim of the present study was to determine the effect of intraplantar injection of anandamide on dorsal spinal neuronal responses in control rats and rats with hindpaw carrageenan-induced inflammation. Effects of intraplantar administration of anandamide (50 microg in 50 microl) on peripheral mechanically-evoked responses of spinal neurones were studied in halothane-anaesthetised rats in vivo. Responses of spinal neurones to mechanical punctate stimulation (von Frey filaments, 8-80 g) of the peripheral receptive field were similar in non-inflamed rats and rats with hindpaw carrageenan-induced inflammation. Intraplantar injection of anandamide, but not vehicle, significantly (P<0.05) inhibited innocuous and noxious mechanically-evoked responses of spinal neurones in rats with hindpaw inflammation, but not in non-inflamed rats. Co-administration of the cannabinoid (2) (CB(2)) receptor antagonist, SR144528 (10 microg in 50 microl), but not the cannabinoid (1) (CB(1)) receptor antagonist, SR141716A (10 microg in 50 microl), significantly blocked inhibitory effects of anandamide on peripheral evoked neuronal responses in rats with hindpaw inflammation. This study demonstrates inhibitory effects of exogenous anandamide on mechanically-evoked responses under inflammatory conditions in vivo, which are mediated by peripheral CB(2) receptors.

Anesthetics, Inhalation↗

PubMed2003

Effects of direct periaqueductal grey administration of a cannabinoid receptor agonist on nociceptive and aversive responses in rats.

The analgesic potential of cannabinoids may be hampered by their ability to produce aversive emotion when administered systemically. We investigated the hypothesis that the midbrain periaqueductal grey (PAG) is a common substrate mediating the anti-nociceptive and potential aversive effects of cannabinoids. The rat formalin test was used to model nociceptive behaviour. Intra-PAG microinjection of the excitatory amino acid D,L-homocysteic acid (DLH) was used to induce an aversive, panic-like reaction characteristic of the defensive "fight or flight" response. Administration of the cannabinoid receptor agonist HU210 (5 microg/rat) into the dorsal PAG significantly reduced the second phase of formalin-evoked nociceptive behaviour, an effect which was blocked by co-administration of the CB(1) receptor antagonist SR141716A (50 microg/rat). This anti-nociceptive effect was accompanied by an HU210-induced attenuation of the formalin-evoked increase in Fos protein expression in the caudal lateral PAG. Intra-dorsal PAG administration of HU210 (0.1, 1 or 5 microg/rat) significantly reduced the aversive DLH-induced explosive locomotor response. The anti-nociceptive effect of HU210 is likely to result from activation of the descending inhibitory pain pathway. Mechanisms mediating the anti-aversive effects of cannabinoids in the PAG remain to be elucidated. These data implicate a role for the PAG in both cannabinoid-mediated anti-nociceptive and anti-aversive responses.

Analysis of Variance↗

PubMed2003

No evidence for activation of alpha(2)-adrenoceptors by methanolic extracts of bovine brain and lung containing clonidine-displacing substance.

Methanolic extracts of bovine brain and lung are capable of displacing [(3)H]-clonidine from alpha(2)-adrenoceptor binding sites, indicating the presence of a clonidine-displacing substance (CDS). We have examined alpha(2)-adrenergic responses and the extracts in three models: [(3)H]-cyclic AMP accumulation in miniprisms of guinea pig cerebral cortex, isometric tension measurements of isolated segments of the rat vas deferens, and porcine palmar lateral vein. The selective alpha(2)-adrenoceptor agonist, 5-bromo-6-2-imidazolin-2-ylamino]-quinoxaline bitartrate (UK-14304) inhibited forskolin-stimulated [(3)H]-cyclic AMP accumulation in the cerebral cortex and elicited contractions of the porcine isolated palmar lateral vein. Clonidine (0.1-30 nM) inhibited neurogenic contractions of the rat vas deferens. Responses to both agonists were inhibited by the alpha(2)-adrenoceptor antagonists, idazoxan or rauwolscine. Brain CDS (5 units/mL) reduced forskolin-stimulated [(3)H]-cyclic AMP accumulation in the guinea pig cerebral cortex, whereas lung CDS (1 unit/mL) increased the accumulation of the cyclic nucleotide. Neither response to the extracts was inhibited by 1 microM idazoxan. Low concentrations of both extracts (0.05 unit/mL) reduced electrically evoked contractions of the rat vas deferens by approximately 20%, but higher concentrations enhanced neurogenic contractions by approximately 50%. Again, the effect of the brain extract was not altered by 1 microM idazoxan. Lung CDS (0.02-1 unit/mL) induced contractions of the porcine palmar lateral vein that were also insensitive to rauwolscine. The results suggest that brain and lung CDS do not activate either central or peripheral alpha(2)-adrenoceptors.

Adrenergic alpha-Agonists↗

PubMed2003

Complex interaction of alpha(2)-adrenoceptor binding sites with bovine brain and lung extracts containing clonidine-displacing substance.

Previous studies have established that methanolic extracts of bovine brain and lung possess CDS activity with an agonist-like profile at alpha(2)-adrenoceptor binding sites (i.e., greater potency against [(3)H]-clonidine sites than against [(3)H]-RX-821001 sites). Following prolonged reflux in ethylacetate, monovalent cations and histamine were removed from the lung extract, and the resulting extract exhibited similar potency against both radioligands, indicative of an antagonist-like profile. These observations help explain the absence of biologic activity at alpha(2)-adrenoceptors in the methanolic extracts as reported in our companion paper.

Animals↗

PubMed2001

Is Ffh required for export of secretory proteins?

In Escherichia coli, protein export from the cytoplasm may occur via the signal recognition particle (SRP)-dependent pathway or the Sec-dependent pathway. Membrane proteins utilize the SRP-dependent route, whereas many secretory proteins use the cytoplasmic Sec machinery. To examine the possibility that signal peptide hydrophobicity governs which targeting route is utilized, we used a series of PhoA signal sequence mutants which vary only by incremental hydrophobicity changes. We show that depletion of SRP, but not trigger factor, affects all the mutants examined. These results suggest secretory proteins with a variety of signal sequences, as well as membrane proteins, require SRP for export.

Alkaline Phosphatase↗

PubMed2001

Cannabinoid activation of recombinant and endogenous vanilloid receptors.

The effects of three structurally related cannabinoids on human and rat recombinant vanilloid VR1 receptors expressed in human embryonic kidney (HEK293) cells and at endogenous vanilloid receptors in the rat isolated mesenteric arterial bed were studied. In the recombinant cells, all three were full agonists, causing concentration-dependent increases in [Ca(2+)](i) (FLIPR), with a rank order of potency relative to the vanilloids capsaicin and olvanil, of olvanil> or =capsaicin>AM404 ((allZ)-N-(4-hydroxyphenyl)-5,8,11,14-eicosatetraenamide)>anandamide>methanandamide. These responses were inhibited by the vanilloid VR1 receptor antagonist, capsazepine. In the mesenteric arterial bed, vasorelaxation was evoked by these ligands with a similar order of potency. The AM404-induced vasorelaxation was virtually abolished by capsaicin pretreatment. AM404 inhibition of capsaicin-sensitive sensory neurotransmission was blocked by ruthenium red, but not by cannabinoid CB(1) and CB(2) receptor antagonists. AM404 had no effect on relaxations to calcitonin gene-related peptide. These data demonstrate that the vasorelaxant and sensory neuromodulator properties of AM404 in the rat isolated mesenteric arterial bed are mediated by vanilloid VR1 receptors.

Acetylcholine↗

PubMed2001

Cannabinoid inhibition of capsaicin-sensitive sensory neurotransmission in the rat mesenteric arterial bed.

The present study investigated whether cannabinoids can modulate neurotransmission mediated by capsaicin-sensitive sensory nerves in the rat isolated mesenteric arterial bed. Sensory neurogenic vasorelaxation mediated by electrical field stimulation was concentration-dependently attenuated by HU210 (0.1-3 microM), a cannabinoid receptor agonist (from 62+/-8.3% to 6+/-2.1% at 3 microM HU210). HU210 had no effect on relaxation to exogenous calcitonin gene-related peptide, indicating a prejunctional action. The action of HU210 (1 microM) was not affected by LY320135 (1 microM) or SR144528 (1 microM), cannabinoid CB(1) and CB(2) receptor antagonists, respectively. SR141716A (0.01-1 microM), a cannabinoid CB(1) receptor antagonist, concentration-dependently augmented vasorelaxation to electrical field stimulation, but had no effect on responses to calcitonin gene-related peptide and capsaicin, indicating a possible role of endogenous cannabinoids in sensory neurotransmission in rat mesenteric arteries. These data show that the cannabinoid receptor agonist HU210 inhibits prejunctionally sensory neurotransmission in rat mesenteric arteries and that this action is independent of cannabinoid CB(1)- or CB(2)-like receptors.

Adenosine Diphosphate↗