Tetrahydrocannabinolic acid reduces nausea-induced conditioned gaping in rats and vomiting in Suncus murinus

BACKGROUND AND PURPOSE

We evaluated the anti-emetic and anti-nausea properties of the acid precursor of Δ⁹-tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), and determined its mechanism of action in these animal models.

EXPERIMENTAL APPROACH

We investigated the effect of THCA on lithium chloride- (LiCl) induced conditioned gaping (nausea-induced behaviour) to a flavour, and context (a model of anticipatory nausea) in rats, and on LiCl-induced vomiting in Suncus murinus. Furthermore, we investigated THCA''s ability to induce hypothermia and suppress locomotion [rodent tasks to assess cannabinoid₁ (CB₁) receptor agonist-like activity], and measured plasma and brain THCA and THC levels. We also determined whether THCA''s effect could be blocked by pretreatment with SR141716 (SR, a CB₁ receptor antagonist).

KEY RESULTS

In rats, THCA (0.05 and/or 0.5 mg·kg⁻¹) suppressed LiCl-induced conditioned gaping to a flavour and context; the latter effect blocked by the CB₁ receptor antagonist, SR, but not by the 5-hydroxytryptamine-1A receptor antagonist, WAY100635. In S. murinus, THCA (0.05 and 0.5 mg·kg⁻¹) reduced LiCl-induced vomiting, an effect that was reversed with SR. A comparatively low dose of THC (0.05 mg·kg⁻¹) did not suppress conditioned gaping to a LiCl-paired flavour or context. THCA did not induce hypothermia or reduce locomotion, indicating non-CB₁ agonist-like effects. THCA, but not THC was detected in plasma samples.

CONCLUSIONS AND IMPLICATIONS

THCA potently reduced conditioned gaping in rats and vomiting in S. murinus, effects that were blocked by SR. These data suggest that THCA may be a more potent alternative to THC in the treatment of nausea and vomiting.     

Inverse agonism of cannabinoid CB1 receptors potentiates LiCl-induced nausea in the conditioned gaping model in rats

BACKGROUND AND PURPOSE

Cannabinoid CB₁ receptor antagonists/inverse agonists, potentiate toxin-induced nausea and vomiting in animal models. Here, we sought to determine if this potentiated nausea was mediated by inverse agonism or neutral antagonism of the CB₁ receptor, and if the potentiated nausea would be produced by intracerebroventricular (icv) administration of an inverse agonist.

EXPERIMENTAL APPROACH

The conditioned gaping model of nausea in rats was used to compare the CB₁ receptor antagonist/inverse agonist, AM251, and the CB₁ receptor neutral antagonists, AM6527 (centrally and peripherally active) and AM6545 (peripherally active), in potentiating conditioned gaping produced by lithium chloride (LiCl) solution. The effect of icv (lateral ventricle and 4th ventricle) administration of AM251 on LiCl-induced gaping in this model was also evaluated.

KEY RESULTS

At a dose that did not produce conditioned gaping on its own, systemically administered AM251 (1.25 mg·kg⁻¹) potentiated LiCl-induced conditioned gaping and reduced sucrose palatability; however, even doses as high as 8 mg·kg⁻¹ of AM6545 and AM6527 neither potentiated LiCl-induced conditioned gaping nor reduced sucrose palatability. Infusions of AM251 into the lateral ventricles (1.25, 12.5 and 125 µg) or the 4th ventricle (2.5, 12.5 and 125 µg) did not potentiate LiCl-induced conditioned gaping reactions, but all doses attenuated saccharin palatability during the subsequent test.

CONCLUSIONS AND IMPLICATIONS

Inverse agonism, but not neutral antagonism, of CB₁ receptors potentiated toxin-induced nausea. This effect may be peripherally mediated or may be mediated centrally by action on CB₁ receptors, located distal to the cerebral ventricles.     

A comparison of cannabidiolic acid with other treatments for anticipatory nausea using a rat model of contextually elicited conditioned gaping

Rationale

The effectiveness of cannabidiolic acid (CBDA) was compared with other potential treatments for anticipatory nausea (AN), using a rat model of contextually elicited conditioned gaping reactions.

Objective

The potential of ondansetron (OND), Δ⁹-tetrahydrocannabinol (THC), chlordiazepoxide (CDP), CBDA, and co-administration of CBDA and tetrahydrocannabinolic acid (THCA) to reduce AN and modify locomotor activity was evaluated.

Materials and methods

Following four pairings of a novel context with lithium chloride (LiCl), the rats were given a test for AN. On the test trial, they received pretreatment injections of the following: vehicle, OND (0.1 or 1.0 mg/kg), THC (0.5 mg/kg), CBDA (0.0001, 0.001, 0.01, 0.1 mg/kg or 1.0 mg/kg), CDP (1, 5, or 10 mg/kg) or co-administration of subthreshold doses of CBDA (0.1 μg/kg), and THCA (5 μg/kg). Immediately following the AN test trial in all experiments, rats were given a 15 min locomotor activity test. Finally, the potential of CBDA (0.001, 0.01, 0.1, and 1 mg/kg) to attenuate conditioned freezing to a shock-paired tone was assessed.

Results

THC, CBDA, and CDP, but not OND, reduced contextually elicited gaping reactions. Co-administration of subthreshold doses of CBDA and THCA also suppressed AN, and this effect was blocked by pretreatment with either a cannabinoid receptor 1 (CB₁) receptor antagonist or a 5-hydroxytryptamine 1A (5-HT_1A) receptor antagonist. CDP (but not CBDA, THC or CBDA and THCA) also suppressed locomotor activity at effective doses. CBDA did not modify the expression of conditioned fear.

Conclusions

CBDA has therapeutic potential as a highly potent and selective treatment for AN without psychoactive or locomotor effects.     

Acute corticosterone increases conditioned spontaneous orofacial behaviors but fails to influence dose related LiCl-induced conditioned "gaping" responses in a rodent model of anticipatory nausea

Acute administration of corticosterone has been shown to facilitate learning in a number of associative paradigms, including LiCl-induced conditioned taste aversion learning. The present study examined the effects of acute corticosterone on LiCl-induced conditioned anticipatory nausea in male rats. Anticipatory nausea is produced by pairing a novel distinctive context with the nausea-inducing effects of a toxin, such as LiCl. Following a number of pairings of the context with the effects of the toxin, rats will display a distinctive conditioned "gaping" response when placed into the context in a drug free state. Adult male Long-Evans rats were injected (intraperitoneal, ip) with a LiCl solution (32, 64, or 128 mg/kg, 0.15M) or saline (NaCl, 0.15 M) followed 10 min later by either corticosterone (5 mg/kg) or β-cyclodextrin vehicle (45%) prior to placement in a distinctive context on four conditioning days (72 h apart) for 30 min. On the conditioning test day rats were placed in the distinctive context in a drug-free state and orofacial and somatic responses were video-recorded for 10 min. Gaping responses increased with increasing doses of LiCl in a linear fashion (P<0.01) but were not significantly influenced by the corticosterone treatment. In contrast, significant increases in the frequency of conditioned spontaneous orofacial behaviors on the drug free test day were produced by the corticosterone treatment during the acquisition phase, whereas LiCl treatment during acquisition had no significant effect on these behaviors. Thus, acute corticosterone did not alter the strength of conditioning of anticipatory nausea in rats.     

The effect of cannabidiol and URB597 on conditioned gaping (a model of nausea) elicited by a lithium-paired context in the rat

Rationale Anticipatory nausea (AN) experienced by chemotherapy patients is resistant to current anti-nausea treatments. In this study, the effect of manipulation of the endocannabinoid (EC) system on a rat model of nausea (conditioned gaping) was determined. Objective The potential of cannabidiol (CBD) and the fatty acid amide hydrolase (FAAH) inhibitor, URB597 (URB) to reduce conditioned gaping in rats were evaluated. Materials and methods In each experiment, rats received four conditioning trials in which they were injected with lithium chloride immediately before placement in a distinctive odor-laced context. During testing, in experiment 1, rats were injected with vehicle (VEH), 1, 5 or 10 mg/kg CBD 30 min before placement in the context previously paired with nausea and in experiment 2, rats were injected with VEH, 0.1 or 0.3 mg/kg URB 2 h before placement in the context. Additional groups evaluated the ability of the CB₁ antagonist/inverse agonist, SR141716A, to reverse the suppressive effects of URB. Experiment 3 measured the potential of URB to interfere with the establishment of conditioned gaping. Results When administered before testing, CBD (1 and 5, but not 10 mg/kg) and URB (0.3, but not 0.1 mg/kg) suppressed conditioned gaping. The effect of URB was reversed by pre-treatment with the CB₁ antagonist/inverse agonist, SR141716A. When administered before conditioning, URB also interfered with the establishment of conditioned gaping. Conclusions Manipulations of the EC system may have therapeutic potential in the treatment of AN.     

昂丹司琼对异氟烷催眠和镇痛作用的影响

目的观察昂丹司琼对异氟烷催眠和镇痛作用的影响;探讨异氟烷的催眠、镇痛作用与5-羟色胺3受体(5-HT3)的关系。方法①催醒实验小鼠ip给予昂丹司琼1,2,4 mg·kg-1,15 min后ip给予异氟烷1.0 ml.kg-1催眠,检测翻正反射消失时间。②催眠半数有效量ED50测定小鼠ip给予昂丹司琼2 mg·kg-1,15 min后用序贯法ip给予异氟烷1.12,0.90,0.72,0.58和0.46 ml.kg-1,测定催眠ED50。③扭体法小鼠ip给予昂丹司琼1,2和4 mg·kg-1,10 min后sc给予异氟烷1.0 ml.kg-1镇痛,检测扭体次数。④热板法小鼠ip给予昂丹司琼1,2和4 mg·kg-1,10 min后,ip给予异氟烷0.4 ml.kg-1镇痛,检测小鼠热板法痛阈值(HPPT)。结果与正常对照组相比,昂丹司琼1,2和4 mg·kg-1组小鼠翻正反射消失持续的时间和ED50值均无明显变化。扭体实验中,与正常对照组比较,昂丹司琼4 mg·kg-1和异氟烷1.0 ml.kg-1可使清醒小鼠扭体次数减少(P<0.01),麻醉小鼠给予昂丹司琼1,2和4 mg·kg-1时,扭体次数有下降趋势,但无统计学差异。热板法中,ip昂丹司琼对清醒小鼠及异氟烷小鼠的HPPT均无明显影响。结论昂丹司琼对异氟烷催眠、抗热刺激伤害作用无明显影响,提示异氟烷的催眠镇痛作用可能与5-HT3受体无明显关系。     

Cannabidiolic acid prevents vomiting in Suncus murinus and nausea-induced behaviour in rats by enhancing 5-HT1A receptor activation

Background and Purpose

To evaluate the ability of cannabidiolic acid (CBDA) to reduce nausea and vomiting and enhance 5-HT_1A receptor activation in animal models.

Experimental Approach

We investigated the effect of CBDA on (i) lithium chloride (LiCl)-induced conditioned gaping to a flavour (nausea-induced behaviour) or a context (model of anticipatory nausea) in rats; (ii) saccharin palatability in rats; (iii) motion-, LiCl- or cisplatin-induced vomiting in house musk shrews (Suncus murinus); and (iv) rat brainstem 5-HT_1A receptor activation by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and mouse whole brain CB₁ receptor activation by CP55940, using [³⁵S]GTPγS-binding assays.

Key Results

In shrews, CBDA (0.1 and/or 0.5 mg·kg⁻¹ i.p.) reduced toxin- and motion-induced vomiting, and increased the onset latency of the first motion-induced emetic episode. In rats, CBDA (0.01 and 0.1 mg·kg⁻¹ i.p.) suppressed LiCl- and context-induced conditioned gaping, effects that were blocked by the 5-HT_1A receptor antagonist, WAY100635 (0.1 mg·kg⁻¹ i.p.), and, at 0.01 mg·kg⁻¹ i.p., enhanced saccharin palatability. CBDA-induced suppression of LiCl-induced conditioned gaping was unaffected by the CB₁ receptor antagonist, SR141716A (1 mg·kg⁻¹ i.p.). In vitro, CBDA (0.1–100 nM) increased the E_max of 8-OH-DPAT.

Conclusions and Implications

Compared with cannabidiol, CBDA displays significantly greater potency at inhibiting vomiting in shrews and nausea in rats, and at enhancing 5-HT_1A receptor activation, an action that accounts for its ability to attenuate conditioned gaping in rats. Consequently, CBDA shows promise as a treatment for nausea and vomiting, including anticipatory nausea for which no specific therapy is currently available.     

Potentiation by low doses of selected neuroleptics of food-induced conditioned place preference in rats

Numerous data support the hypothesis that dopamine (DA) plays a crucial role in reward-related processes and in incentive learning in animals and man. The possibility that various neuroleptics exhibiting a high affinity for the dopaminergic D₂ (and D₃) receptors could reinforce DA transmission was studied using the conditioned place preference paradigm (CPP) in rats. This was done by examining the ability of these compounds to potentiate the reinforcing properties of food in hungry rats subjected to a version of the CPP paradigm which consisted of repeated pairings of food with a single environmental cue, the floor texture of an open field. During the test session when food was no longer available in the open field, the increase in the time spent by drug-free rats on the food-paired texture was assumed to indicate the perceived rewarding value of the food. This time was significantly lengthened when the specific D₂ (D₃)-receptor antagonists sulpiride (4 mg/kg), amisulpride (0.5, 1 mg/kg) or pimozide (0.03, 0.06 mg/kg) were administered before the food conditioning sessions. Larger doses of these compounds as well as haloperidol, metoclopramide and the non-specific D₁-D₂ antagonist, chlorpromazine, regardless of the doses tested, did not exhibit this effect, but rather reduced the food-induced CPP, an action usually associated with neuroleptics. The positive effects of amisulpride was reversed by a D₁ receptor antagonist, SCH 23390 (0.01 mg/kg). These results suggest that, as with amphetamine (0.5 mg/kg), some D₂-specific neuroleptics enhance the incentive value of food in a narrow range of low doses, an effect proposed to reflect a prohedonic property. The potentiation of the release of DA unconditionally evoked by food, through a selective blockade of the release-modulating D₂-autoreceptors, could constitute the neurobiological substratum of this effect. A concomitant blockade of either D₂ or D₁ postsynaptic receptors, however, appeared to be sufficient to counteract such activity.     

Effect of hippocampal lesion on acquisition of conditioned avoidance behaviour in albino rats

Control, hippocampal and Sham control male albino rats weighing 150-200 gms were trained for acquisition of conditioned avoidance behavioural response using escape avoidance apparatus. Parameters like rate of performance, error scores, conditioned stimulus latency and unconditioned stimulus latency were studied. It was observed that there was a facilitation in the behavioural response with less error scores in hippocampal animals as compared to Sham control and control groups. Our observations are similar to those of Douglas and Pribram and Douglas and it is concluded that the hippocampus acts as a gate restricting the range of stimuli to which an intact animal attends.     

The biphasic effect of small doses of tranylcypromine on the spontaneous motor activity and learned conditioned behaviour in rats

Tranylcypromine (TCP), a monoamine-oxidaone inhibitor with amphetamine-like property, has at first a depressant effect and 5 h later a stimulating effect on sponataneous motor activity and learned conditioned behaviour. This latter effect can be demonstrated by means of a modified conditioned avoidance response schedule and a specific time-schedule interval. While the depressant effect of tranylcypromine may be due to the initial increase of brain serotonin caused by this drug, its delayed stimulating effect is, very likely, related to norepinephrine brain increase occurring a few hours after TCP administration.     

Potential of the rat model of conditioned gaping to detect nausea produced by rolipram, a phosphodiesterase-4 (PDE4) inhibitor

Rolipram, a phosphodiesterase-4 (PDE4) inhibitor, is of current interest as a cognitive enhancer and as a treatment for inflammatory diseases. Originally developed as an anti-depressant, rolipram's efficacy was limited due to its side effects of nausea and vomiting. The experiments reported here evaluated the potential of rolipram to produce conditioned gaping (a selective measure of nausea in rats) to a flavor in the taste reactivity test (Experiment 1) and to a context (Experiment 2). In Experiment 1, rats were intra-orally infused with 17% sucrose solution prior to being injected with rolipram (Vehicle, 0.03, 0.1 or 0.3 mg/kg). Following 3 conditioning trials, rats conditioned with 0.3 mg/kg rolipram displayed conditioned gaping reactions during the infusion of sucrose. In Experiment 2, rats received 4 conditioning trials in which they were injected with 0.3 mg/kg rolipram and placed into a distinctive chamber. At test, when returned to the chamber rats displayed conditioned gaping. These results demonstrate the ability of the conditioned gaping model to detect the nauseating properties of a rolipram-paired flavor (Experiment 1) and rolipram-paired context (Experiment 2), further validating the potential use of the conditioned gaping model as a pre-clinical screening tool to evaluate the side effect of nausea produced by newly developed drugs.     

Dopamine toxicity following long term exposure to low doses of 3-nitropropionic acid (3-NPA) in rats

A toxin produced by legumes of the genus Astragalus and Arthrinium fungi, 3-NPA is a suicide inhibitor of succinate dehydrogenase and causes acute encephalopathy and late onset dystonia. It has been suggested that dopamine (DA) toxicity plays a role in 3-NPA induced brain damage. In order to simulate natural conditions of toxicant intake, adult, male, Sprague-Dawley rats were exposed to 3-NPA weekly for 24-h periods at 10 and 20 mg/40 ml in drinking water. This dosing regimen continued for 3 months with animals from both high and low dose groups sacrificed at the end of each month. Dopamine and its metabolites, 3,4-dihydroxylphenylacetic acid (DOPAC) and homovanillic acid (HVA), were assessed by HPLC-EC in the frontal cortex (FC) and caudate nucleus (CN). Increases of DA concentration were seen in both low and high dose groups in the CN after 1 and 3 months of dosing and in the FC after 2 months of exposure. An increase in DA turnover was observed in the CN of the high dose group following 2 months of dosing. Data suggest an activation of the dopaminergic system after long-term, intermittent exposure to 3-NPA. The production of radical oxygen species associated with DA metabolism may contribute to 3-NPA-induced neurotoxicity.     

The aphrodisiac effect of low doses of (-) deprenyl in male rats

The effects of single doses of (-)deprenyl, in comparison to J-508, U-1424, pargyline and clorgyline, on the sexual performance of male rats were tested. (-)Deprenyl (0.25 and 1 mg/kg, respectively) exerted a true, long-lasting aphrodisiac effect, on sexually sluggish male rats, whereas clorgyline, U-1424 and J-508 failed to act similarly. Pargyline facilitated the sexual performance of the rats, but only transiently.     

Nicotine induces conditioned place preferences over a large range of doses in rats

Rationale Conditioned place preference (CPP) procedures provide one measure of potential rewarding effects of abused drugs. Many attempts to induce CPP with nicotine have been unsuccessful.Objectives To assess the influence of nicotine dose and stimulus assignment procedure on development of nicotine-induced CPP.Methods Initial preferences for one side of a two-compartment apparatus were first determined in Sprague–Dawley rats. In subsequent conditioning trials, the compartment paired with nicotine was the initially preferred side for half of the rats, and the initially non-preferred side for the other half. Rats received either an injection of nicotine (0.01–2 mg/kg SC) before being placed in one compartment (three trials) or saline before being placed in the other compartment (three trials). Control rats had saline injections associated with both compartments. A final test trial with no injection assessed final place preference.Results Significant CPP were induced by 0.1–1.4 mg/kg doses of nicotine. Nicotine-induced CPP were only apparent when nicotine was paired with the initially non-preferred side. Moreover, a very high dose of nicotine (2 mg/kg) induced conditioned place aversion when paired with the initially preferred side of the apparatus.Conclusions Nicotine induced significant CPP across a wide range of doses, in accordance with its role as the primary addictive component of tobacco. Small preferences for one side of the apparatus played a major role in the development of nicotine-induced CPP. These findings suggest that biased procedures may be more suitable than unbiased procedures for evaluation of rewarding effects of nicotine using CPP paradigms.     

Effect of low doses of a trichothecene mycotoxin (diacetoxyscirpenol) on rat gastric glycoproteins: a histochemical study

A histochemical study was carried out to evaluate the changes occurring in the glycoproteins of the stomach of the rat following short-term treatment with the trichothecene mycotoxin, diacetoxyscirpenol (DAS). Staining with alcian blue methods for detecting complex carbohydrates and with lectin conjugates (Con A, LTA, PNA, SBA and WGA) showed an increased alcianophilia at pH 2.6 and pH 1.0 for various parts of the fundic glands. With respect to lectin staining, DAS intoxication was characterized by enhanced labelling with LTA and SBA in the surface epithelium and in the foveolae, while WGA binding appeared in the lower mucous neck cells. These data suggest that the contents of the mucus-producing cells of the fundic glands of the rat stomach could be affected by low doses of diacetoxyscirpenol even following only 2 days of treatment.     

Effect of MDMA (ecstasy) on activity and cocaine conditioned place preference in adult and adolescent rats

MDMA (ecstasy) is a drug commonly used in adolescence, and many users of MDMA also use other illicit drugs. It is not known whether MDMA during adolescence alters subsequent responses to cocaine differently than in adults. This study examined the effects of MDMA in adolescent and adult rats on cocaine conditioned reward. At the start of these experiments, adolescent rats were at postnatal day (PND) 33 and adult rats at PND 60. Each rat was treated for 7 days with MDMA (2 or 5 mg/kg/day or vehicle) and locomotor activity was measured. Five days later cocaine conditioned place preference (CPP) was begun. Rats were trained for 3 days, in the morning with saline and in the afternoon with 10 mg/kg cocaine in 30 min sessions, and tested on the fourth day. MDMA stimulated activity in both age groups, but with a greater effect in the adult rats. Sensitization to the locomotor-stimulant effects of the lower dose of MDMA occurred in adult rats and in both groups to the higher dose. Cocaine did not produce a CPP in vehicle-treated adolescent rats, but a significant CPP was observed subsequent to treatment with MDMA. In contrast, cocaine-induced CPP was diminished after MDMA in adult rats. These effects were still evident 2 weeks later upon retest. Thus, under the present conditions, MDMA increased cocaine conditioned reward in adolescent and decreased it in adult rats. These findings suggest that exposure to MDMA during this critical developmental period may carry a greater risk than during adulthood and that male adolescents may be particularly vulnerable to the risk of stimulant abuse after use of MDMA.     

Low and high doses of midazolam differentially affect hypoalgesia in rats conditioned to a heat stressor

These experiments examined the effects of a benzodiazepine (midazolam) on rats' sensitivity-reactivity to the heated floor of a hot-plate apparatus. Rats were either previously exposed to the heated floor, or naive to the hot-plate apparatus, while control rats were familiarized with the apparatus in the absence of pain. A low dose (0.63 or 1.25 mg/kg) of midazolam attenuated the conditioned hypoalgesic response resulting from pre-exposure to a heated floor, but did not affect the hypoalgesic response elicited by exposure to a novel hot-plate apparatus nor the baseline sensitivity-reactivity among control rats. A high dose (2.5 mg/kg) of midazolam resulted in a naloxone-insensitive increase in both the conditioned and the novelty-induced hypoalgesia, and provoked a small, but naloxone-reversible increase in paw-lick latencies among control rats. The results were taken to mean that exposure to the heated floor results in hypoalgesic responses as a consequence of fear conditioning and the reinstatement of novelty. Midazolam was assumed to attenuate conditioned hypoalgesia by reducing fear but at the high dose to augment the hypoalgesic effects of novelty.     

Assessment of acute behavioral toxicity of low doses of diisopropylfluorophosphate (DFP) in rats.

The effect on behavior of single subtoxic doses (100 and 600 micrograms/kg i.p., i.e. 1/77 and 1/13 of LD50, respectively) of an organophosphorous compound, diisopropylfluorophosphate (DFP), was studied in male Wistar rats. In the open-field test, the lower dose of DFP tended to increase ambulation, while the higher dose showed a trend towards a decrease in ambulation, rearing and frequency of defecation. In the elevated plus-maze, rotarod, elevated bridges and hot plate tests, DFP-treated rats did not differ significantly from the olive oil-treated controls. DFP significantly impaired the performance of rats in the one-trial passive avoidance task and dose-dependently decreased spontaneous locomotor activity for 4 hours after administration. At the doses used DFP only slightly inhibited acetylcholinesterase activity in the blood and different brain areas. The results show that the higher dose of DFP had an inactivating effect on the behavior of rats, while the lower dose did not markedly change their behavioral pattern. Our findings indicate that anticholinesterase compounds, such as DFP, can alter behavior even after single small subtoxic doses.