How is small bowel permeability in endometriosis patients? a case control pilot study.

Endometriosis is a chronic inflammatory disease of women of reproductive age. Small bowel (SB) permeability and lipopolysaccharides (LPS) could play a role in the perduration of low grade inflammation status and the pathogenesis of endometriosis. To clarify this hypothesis, we measured SB permeability through plasma values of LPS and urinary secretion of lactulose (La), mannitol (Ma) and their ratio (L/M) in patients with endometriosis compared with healthy controls (HC). Eight patients and 14 HC entered the study. SB permeability was evaluated by high-performance liquid chromatography of urine concentrations of La and Ma. Plasma levels of LPS were measured in the blood. Moreover, a nutritional, gastroenterological, quality of life evaluation was performed through validates questionnaires and complete gynaecological evaluations. The statistical analysis of the obtained data did not show differences in anthropometric and nutritional characteristics and gastrointestinal functional disease in the two groups. Patients reported higher levels of pelvic chronic pain (3.87 ± 2.99 vs 0.15 ± 0.55; pe = 0.001) and significantly higher LPS plasma levels (0.529 ± 0.11 vs 0.427 ± 0.08; p value = .027) than HC. Our results indicate that intestinal permeability is abnormal in endometriosis patients, and it might play a role in the pathogenesis of this chronic disease.

Chronic URB597 treatment at adulthood reverted most depressive-like symptoms induced by adolescent exposure to THC in female rats.

We have recently shown that chronic THC administration in adolescent female rats induces subtle but lasting alterations in the emotional circuit ending in depressive-like behaviour at adulthood. Here we describe other relevant depressive-like symptoms present in these animals. Adult female rats pretreated with THC display passive coping strategy towards acute stressful situations as demonstrated by their behaviours in the first session of the forced swim test, develop a profound anhedonic state as demonstrated by the reduced consumption of palatable food and present a decrease in social functioning. Besides the emotional symptoms, adolescent exposure to THC induced a significant deficit in object recognition memory. Since it has been reported that deficits in adult hippocampal neurogenesis may underlie the cognitive dysfunction seen in depression, we then survey cell proliferation in the dentate gyrus of the hippocampus. Adolescent THC exposure significantly reduced the number of BrdU-positive cells in THC-treated rats as well as hippocampal volume. We suggest that this complex depressive-like phenotype is triggered by a long-lasting decrease in CB1 receptor functionality in specific brain regions. To test whether an increase in the endocannabinoid signalling could ameliorate the depressive phenotype, adult female rats pre-exposed to THC were injected with URB597 (0.3mg/kg ip) and then tested in behavioural assays. URB597 was able to reverse most depressive-like symptoms induced by adolescent THC exposure such as the passive coping strategy observed in THC exposed animals in the forced swim test as well as anhedonia and the reduced social activity. These results support a role for the endocannabinoid system in the neurobiology of depression and suggest the use of URB597 as a new therapeutic tool with antidepressant properties.

Cellular mechanisms underlying the interaction between cannabinoid and opioid system.

Recently, the presence of functional interaction between the opioid and cannabinoid system has been shown in various pharmacological responses. Although there is an increasing interest for the feasible therapeutic application of a co-administration of cannabinoids and opioids in some disorders (i.e. to manage pain, to modulate immune system and emotions) and the combined use of the two drugs by drug abusers is becoming largely diffuse, only few papers focused on cellular and molecular mechanisms underlying this interaction. This review updates the biochemical and molecular underpinnings of opioid and cannabinoid interaction, both within the central nervous system and periphery. The most convincing theory for the explanation of this reciprocal interaction involves (i) the release of opioid peptides by cannabinoids or endocannabinoids by opioids, (ii) the existence of a direct receptor-receptor interaction when the receptors are co-expressed in the same cells, and (iii) the interaction of their intracellular pathways. Finally, the cannabinoid/opioid interaction might be different in the brain rewarding networks and in those accounting for other pharmacological effects (antinociception, modulation of emotionality and cognitive behavior), as well as between the central nervous system and periphery. Further insights about the cannabinoid/opioid interaction could pave the way for new and promising therapeutic approaches.

The depressive phenotype induced in adult female rats by adolescent exposure to THC is associated with cognitive impairment and altered neuroplasticity in the prefrontal cortex.

We recently demonstrated that Delta(9)-tetrahydrocannabinol (THC) chronic administration in female adolescent rats induces alterations in the emotional circuit ending in depressive-like behavior in adulthood. Since cognitive dysfunction is a major component of depression, we assessed in these animals at adulthood different forms of memory. Adolescent female rats were treated with THC or its vehicle from 35 to 45 post-natal days (PND) and left undisturbed until their adulthood (75 PND) when aversive and spatial memory was assessed using the passive avoidance and radial maze tasks. No alteration was found in aversive memory, but in the radial maze THC pre-treated animals exhibited a worse performance than vehicles, suggesting a deficit in spatial working memory. To correlate memory impairment to altered neuroplasticity, level of marker proteins was investigated in the hippocampus and prefrontal cortex, the most relevant areas for learning and memory. A significant decrease in synaptophysin and PSD95 proteins was found in the prefrontal cortex of THC pre-treated rats, with no alterations in the hippocampus. Finally, proteomic analysis of the synapses in the prefrontal cortex revealed the presence of less active synapses characterized by reduced ability in maintaining normal synaptic efficiency. This picture demonstrates the presence of cognitive impairment in THC-induced depressive phenotype.

Role in anxiety behavior of the endocannabinoid system in the prefrontal cortex.

In the present study we explored with a multidisciplinary approach, the role of anandamide (AEA) in the modulation of anxiety behavior at the level of the prefrontal cortex (PFC). Low doses of the metabolically stable AEA analog, methanandamide, microinjected into the PFC, produced an anxiolytic-like response in rats, whereas higher doses induced anxiety-like behaviors. Pretreatment with the selective antagonist of CB1 or TRPV1 receptors (AM251 and capsazepine, respectively) suggested that the anxiolytic effect evoked by AEA might be due to the interaction with the CB1 cannabinoid receptor, whereas vanilloid receptors seem to be involved in AEA anxiogenic action. When AEA contents in the PFC were increased by microinjecting the selective inhibitor of fatty acid amide hydrolase (FAAH), URB597, we observed an anxiolytic response only at low doses of the compound and no effect or even an anxiogenic profile at higher doses. In line with this, a marked decrease of AEA levels in the PFC, achieved by lentivirus-mediated local overexpression of FAAH, produced an anxiogenic response. These findings support an anxiolytic role for physiological increases in AEA in the PFC, whereas more marked increases or decreases of this endocannabinoid might lead to an anxiogenic response due to TRPV1 stimulation or the lack of CB1 activation, respectively.

CB1 receptor stimulation in specific brain areas differently modulate anxiety-related behaviour.

There is a general consensus that the effects of cannabinoid agonists on anxiety seem to be biphasic, with low doses being anxiolytic and high doses ineffective or possibly anxiogenic. Besides the behavioural effects of cannabinoids on anxiety, very few papers have dealt with the neuroanatomical sites of these effects. We investigated the effect on rat anxiety behavior of local administration of THC in the prefrontal cortex, basolateral amygdala and ventral hippocampus, brain regions belonging to the emotional circuit and containing high levels of CB1 receptors. THC microinjected at low doses in the prefrontal cortex (10 microg) and ventral hippocampus (5 microg) induced in rats an anxiolytic-like response tested in the elevated plus-maze, whilst higher doses lost the anxiolytic effect and even seemed to switch into an anxiogenic profile. Low THC doses (1 microg) in the basolateral amygdala produced an anxiogenic-like response whereas higher doses were ineffective. All these effects were CB1-dependent and closely linked to modulation of CREB activation. Specifically, THC anxiolytic activity in the prefrontal cortex and ventral hippocampus was paralleled by an increase in CREB activation, whilst THC anxiogenic response in the basolateral amygdala was paralleled by a decrease in CREB activation. Our results suggest that while a mild activation of CB1 receptors in the prefrontal cortex and ventral hippocampus attenuates anxiety, a slight CB1 receptor stimulation in the amygdala results in an anxiogenic-like response. The molecular underpinnings of these effects involve a direct stimulation of CB1 receptors ending in pCREB modulation and/or a possible alteration in the fine tuning of local neuromodulator release.

Molecular bases of type II protein S deficiency: the I203-D204 deletion in the EGF4 domain alters GLA domain function.

OBJECTIVE: To characterize the first type II protein S (PS) deficiency affecting the epidermal growth factor (EGF)4 domain, a calcium-binding module with a poorly defined functional role. PATIENTS: The proband suffered from recurrent deep vein thrombosis and showed reduced PS anticoagulant activity (31%), and total, free PS antigen and C4bBP levels in the normal range. RESULTS: Reverse transcription-polymerase chain reaction analysis showed the presence of the IVSg-2A/T splicing mutation that, by activating a cryptic splice site, causes the deletion of codons Ile203 and Asp204. Free PS, immunopurified from proband's plasma, showed an altered electrophoretic pattern in native condition or in the presence of Ca2+. The recombinant PS (rPS) mutant showed reduced anticoagulant (<10%) and activated protein C-independent activities (24-38%) when compared with wild-type rPS (rPSwt). Binding of the rPS variant to phospholipid vesicles (Kd 235.7 +/- 30.8 nM, rPSwt; Kd 15.2 +/- 0.9 nM) as well as to Ca2+-dependent conformation-specific monoclonal antibodies for GLA domain was significantly reduced. CONCLUSIONS: These data aid in the characterization of the functional role of the EGF4 domain in the anticoagulant activities of PS and in defining the thrombophilic nature of type II PS deficiency.

[Protein C and coagulation in sepsis]. / La proteina C e la coagulazione nella sepsi.

The last few years have clarified the tight link between inflammation and coagulation. In addition to the identification of new regulatory mechanisms of the coagulation system and of an explosive number of mediators of inflammation, it is now clear that the existence of a positive feed-back between inflammation and coagulation leads to reciprocal activation of both pathways. Plasma levels of acute phase proteins involved in coagulation and fibrinolysis are elevated during inflammation, while natural anticoagulant mechanisms are depressed. Pro-inflammatory cytokines "activate" cell membranes exposed to flowing blood (endothelium, platelets, monocytes, neutrophils) which from physiologically inert or anticoagulant become procoagulant. Increased tissue factor expression results in increased thrombin formation within the microcirculation. Thrombin is central to fibrin deposition but it also plays a key role in cell-mediated mechanisms involving inflammation, cell proliferation and activation of the natural anticoagulant protein C. Depression of natural anticoagulant mechanisms, occurring in severe sepsis, results in uncontrolled thrombin formation, with pro-inflammatory activity prevailing, and the feed-back loop of inflammation and coagulation ultimately leading to multi-organ failure. However, both in the clinical setting and in animal experiments, heparin or direct anticoagulants have shown no effect on survival even if blocking fibrin deposition. Organ failure is only partially due to the thrombotic occlusion of the microcirculation, while other mechanisms of endothelial damage are probably more relevant in the development of ischemia. The endothelium is central to the maintenance of the natural anticoagulant mechanisms (TFPI, antithrombin, protein C). The protein C system, in addition to dumping thrombin formation, specifically modulates inflammation by cell signaling. This system is markedly depressed in severe sepsis. The infusion of activated protein C, or restoring normal levels of protein C within the circulation - depending on the individual bleeding risk are powerful tools to treat the endothelitis responsible for the clinical sequelae of severe sepsis.

Differential diurnal variations of anandamide and 2-arachidonoyl-glycerol levels in rat brain.

The endogenous ligands of cannabinoid receptors, also known as endocannabinoids, have been implicated in many physiological and pathological processes of the central nervous system. Here we show that the levels of the two major endocannabinoids, anandamide and 2-arachidonoyl-glycerol (2-AG), in four areas of the rat brain, change dramatically between the light and dark phases of the day. While anandamide levels in the nucleus accumbens, pre-frontal cortex, striatum and hippocampus were significantly higher in the dark phase, the opposite was observed with 2-AG, whose levels were significantly higher during the light phase in all four regions. We found that the activity of the fatty acid amide hydrolase, which catalyzes the metabolism of anandamide, was significantly lower during the dark phase, thus providing a possible explaination for the increase in anandamide levels. However, the activities of monoacylglycerol lipase and diacylglycerol lipase, two of the possible enzymes catalyzing the degradation and biosynthesis of 2-AG, respectively, changed significantly only in the striatum. These data suggest that the levels of the two major endocannabinoids might be under the control of endogenous factors known to undergo diurnal variations, and underscore the different roles, suggested by previous studies, of anandamide and 2-AG in neurophysiological processes.

Mu opioid receptor signaling in morphine sensitization.

We used a previously reported model of morphine sensitization that elicited a complex behavioral syndrome involving stereotyped and non stereotyped activity. To identify the mechanism of these long-lasting processes, we checked the density of mu opioid receptors, receptor-G-protein coupling and the cyclic AMP (cAMP) cascade. In morphine-sensitized animals mu opioid receptor autoradiography revealed a significant increase in the caudate putamen (30% versus controls), nucleus accumbens shell (16%), prefrontal and frontal cortex (26%), medial thalamus (43%), hypothalamus (200%) and central gray (89%). Concerning morphine's activation of G proteins in the brain, investigated in the guanylyl 5'-[gamma-(35)S]thio]triphosphate ([(35)S]GTPgammaS) binding assay, a significant increase in net [(35)S]GTPgammaS binding was seen in the caudate putamen (39%) and hypothalamus (27%). In the caudate putamen this was due to an increase in the amount of activated G proteins, and in the hypothalamus to a greater affinity of G proteins for guanosine triphosphate (GTP). The main second messenger system linked to the opioid receptor is the cAMP pathway. In the striatum basal cAMP levels were significantly elevated in sensitized animals (70% versus controls) and [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO) significantly inhibited forskolin-stimulated cAMP production in control (30%) but not in sensitized rats. In the hypothalamus no significant changes were observed in basal cAMP levels and DAMGO inhibition. These cellular events induced by morphine pre-exposure could underlie the neuroadaptive processes involved in morphine sensitization.

Cellular mechanisms of Delta 9-tetrahydrocannabinol behavioural sensitization.

We investigated the cellular events linked to the induction of cannabinoid behavioural sensitization. In sensitized rats, autoradiographic binding studies with [3H]CP-55,940 showed a significant increase in cannabinoid receptor binding, specifically in the cerebellum, with no changes in the other brain areas where basal CB1-receptor expression is observed. In vitro autoradiography of CP-55,940-stimulated [35S]GTP gamma S binding provided a picture of cannabinoid receptor-mediated G protein activation. Basal [35S]GTP gamma S binding was not affected, whereas sensitized rats showed a significant increase of net [35S]GTP gamma S binding in the caudate putamen and cerebellum. Autoradiographic studies suggested that only these two areas had altered receptor functionality. We therefore focused our intracellular investigations only there, first surveying the responsiveness of the cAMP system to cannabinoids. CP-55,940 was unable to inhibit forskolin-induced cAMP accumulation in the cerebellum of sensitized animals, but no difference was observed between groups in the caudate putamen. Finally, we surveyed the levels of CREB and AP-1 binding activity, in the same two areas and found no difference in sensitized rats. The intracellular picture in sensitized rats suggests that besides the cAMP cascade, other signalling pathways may participate in the development of cannabinoid sensitization.

Relationship between international normalized ratio values, vitamin K-dependent clotting factor levels and in vivo prothrombin activation during the early and steady phases of oral anticoagulant treatment.

BACKGROUND AND OBJECTIVES: In vitro studies have shown that the rate of prothrombin activation is linearly related to the concentration of factor II (FII) in the assay system, suggesting a key role of prothrombin levels in the expression of the antithrombotic activity of oral anticoagulant treatment (OAT). We investigated the in vivo relationship between prothrombin activation and vitamin K-dependent clotting factor levels during the early and steady phases of OAT in patients and in healthy volunteers. DESIGN AND METHODS: The changes in international normalizezd ratio (INR) and in the plasma levels of FVII, FX, FII, protein C (PC) and prothrombin fragment 1.2 (F1+2) induced by OAT were monitored over 9 days in 10 patients not on heparin starting warfarin after heart valve replacement (HVR) and in 9 healthy volunteers submitted to an 8-day course of warfarin treatment. FII and F1+2 plasma levels were also measured in 100 patients on stable oral anticoagulant treatment with INRs ranging from 1.2 to 6.84. RESULTS: Because HVR patients had subnormal FVII, FX and FII levels after surgery, INR values > 2.0 were attained already 24 hours after the first warfarin dose. In healthy volunteers, INR values greater than 2.0 were first observed after 72 hours. Nadir levels of FVII, PC, FX and FII were reached between 40 and 88 hours in HVR patients and between 72 and 192 hours in healthy volunteers. The FII apparent half-disappearance time (t/2) was 99 hours in HVR patients and 115 hours in healthy volunteers (p = ns). In HVR patients there was no normalization of initially elevated F1+2 levels until day 7 with an apparent t/2 of 132 hours. In healthy volunteers, a decrease to subnormal F1+2 levels was observed by day 8 of treatment (apparent t/2 = 107 hours). In both HVR patients and healthy volunteers, FII and PC levels were independent predictors of the changes in F1+2 levels (p = 0.0001). In patients on stable OAT, only FII levels were independent predictors of the variation in F1+2 levels (p = 0.0001). INTERPRETATION AND CONCLUSIONS: During the early phase of oral anticoagulant treatment in vivo prothrombin activation is a function of the balance between FII and PC levels and is not significantly prevented until nadir levels of FII are obtained. This provides an explanation for the requirement of overlapping heparin and oral anticoagulant treatment for at least 48 hours after the achievement of therapeutic INR values in patients with thromboembolic diseases. In addition, in vivo prothrombin activation is a function of FII levels rather than INR values also in patients on stable oral anticoagulant treatment.

Normalization rates of compression ultrasonography in patients with a first episode of deep vein thrombosis of the lower limbs: association with recurrence and new thrombosis.

BACKGROUND AND OBJECTIVES: Delayed thrombus regression after a first episode of deep vein thrombosis (DVT) of the inferior limbs has been implicated in the development of the post-thrombotic syndrome. Whether normalization of vein segments involved in the index DVT has prognostic significance with respect to the probability of DVT recurrence or new thrombosis is currently unknown. In this study, we prospectively monitored thrombus regression in consecutive patients with symptomatic and asymptomatic DVT. Factors affecting normalization rates and the relationship between previous normalization and DVT recurrence or new thrombosis were explored. DESIGN AND METHODS: One hundred and seventy-nine patients with a first episode of symptomatic DVT of the lower limbs (38 with cancer) and 104 patients with DVT occurring after hip replacement surgery were serially monitored by real time B-mode compression ultrasonography (C-US) over a period of 12 months (months 1, 3, 6 and 12). C-US normalization of popliteal and femoral venous segments was arbitrarily assigned to be residual thrombus occupying, at maximum compressibility, less than 40% of the vein area in the absence of compression. RESULTS: In patients with no DVT recurrence or new thrombosis, C-US normalization was observed at 12 months in 100% of 99 patients with post-operative DVT, in 59% of 134 cancer-free symptomatic DVT outpatients and in 23.3% of 30 symptomatic DVT outpatients with cancer (p = 0.0001). Independent negative effects on the probability of C-US normalization were observed for younger age (p <0.05), for the outpatient presentation of the index DVT (p 0.017), for DVT involving the entire femoro-popliteal axis (p 0.05), and for the presence of cancer (p 0.05). DVT recurrence or new thrombosis was observed in 5 patients with post-operative DVT (4.8%), in 7 cancer-free patients with symptomatic DVT (5.0%) and in 8 patients with cancer (21.1%). Only 4 of these patients had shown normalization of their index DVT prior to the event. The presence of cancer was the only significant predictor of DVT recurrence and/or new thrombosis occurring within 3 months from the index DVT (OR = 4.90, p = 0.002). The absence of previous C-US normalization was the only predictor of recurrence or new thrombosis occurring after 3 and 6 months from the index DVT (OR 5.26, p 0.027). INTERPRETATION AND CONCLUSIONS: Absence of C-US normalization after a first episode of DVT appears to be a factor favoring recurrence or new thrombosis and may be relevant to the optimal duration of oral anticoagulant treatment.

The psychoactive ingredient of marijuana induces behavioural sensitization.

Here we describe, for the first time, the occurrence of behavioural sensitization after chronic exposure to Delta9-tetrahydrocannabinol. Rats were treated twice a day, for five days, with increasing doses (5, 10, 20, 40, 40 mg/kg i.p.) of Delta9-tetrahydrocannabinol or its vehicle and after 20 days of withdrawal, animals were challenged with 5 mg/kg (i.p.) of the drug and their behaviour was assessed. Contrary to the motor inhibition induced in control rats, challenge with Delta9-tetrahydrocannabinol in pre-exposed animals elicited a complex behavioural syndrome mainly characterized by oral stereotyped items. Due to the relevance of behavioural sensitization in drug-seeking behaviour that persists long after discontinuation of drug use, our findings suggest that cannabinoids could trigger neurobiological alteration not dissimilar from those observed with more harmful abused drugs.

A study of light/dark rhythm of melatonin in relation to cortisol and prolactin secretion in schizophrenia.

OBJECTIVES: Recent studies have suggested the involvement of the pineal gland and its main hormone melatonin (MLT) in the pathogenesis of psychiatric disturbances, namely the depressive syndrome. In contrast, the behavior of MLT secretion in schizophrenia is still controversial. MATERIAL & METHODS: The present study was carried out to analyze light/dark rhythm of MLT secretion in relation to that of cortisol and prolactin (PRL) in schizophrenic patients. The study included 13 schizophrenic patients, 8 of whom were untreated, while the other 5 patients were on neuroleptic therapy. Serum levels of MLT, PRL and cortisol were measured by RIA on venous blood samples collected at 8 A.M., 12 A.M., 8 P.M. and 1 A.M. The control group consisted of 20 age-matched healthy subjects. RESULTS: A physiological nocturnal increase in MLT levels occurred in 6/13 patients, whereas the other 7 patients showed an abnormally low MLT peak during the night. Moreover, both light and night mean levels of MLT were significantly lower in patients than in controls. In addition, mean nocturnal levels of MLT were significantly lower in chronic patients than in those evaluated at the onset of disease. Cortisol rhythm was normal in 11/13 patients, whereas PRL levels were abnormally high in 10/13 patients. CONCLUSIONS: This preliminary study would suggest that schizophrenia may be associated with a diminished secretion of MLT from the pineal gland, and pineal deficiency would be more evident in the chronic disease. Finally, pineal alterations have appeared to be associated with an altered secretion of PRL and cortisol, by suggesting that the schizophrenic disease may be characterized by marked neuroendocrine disturbances, whose physio-pathological and prognostic significance needs to be established by successive clinical investigations.

Loss of cannabinoid-stimulated guanosine 5'-O-(3-[(35)S]Thiotriphosphate) binding without receptor down-regulation in brain regions of anandamide-tolerant rats.

The endogenous cannabinoid anandamide has been reported to produce well-defined behavioral tolerance, but studies on the possible mechanisms underlying this process are few and often contradictory. The present study was designed to survey the cellular events involved in anandamide tolerance, in terms of the effects on receptor number, coupling with G proteins, and activation of the cyclic AMP (cAMP) cascade. Chronic treatment of rats with anandamide (20 mg/kg i.p. for 15 days) resulted in behavioral tolerance without any change in cannabinoid receptor binding in the brain regions studied (striatum, cortex, hippocampus, and cerebellum), suggesting that receptor down-regulation was not involved in the development of anandamide behavioral tolerance. In contrast, prolonged exposure to anandamide significantly reduced agonist-stimulated guanosine 5'-O:-(3-[(35)S]thiotriphosphate) binding in the same areas, with losses of >50%, suggesting that receptor desensitization may be part of the molecular mechanism underlying this tolerance. Finally, concerning the cAMP cascade-the most well-known intracellular signaling pathways activated by CB(1) receptors-in the brain regions from rats tolerant to anandamide, we found no alteration in cAMP levels or in protein kinase A activity. We propose that anandamide, unlike Delta(9)-tetrahydrocannabinol and other cannabinoids, does not alter the receptor system at multiple levels but that desensitization of the CB(1) receptor might account for behavioral tolerance to the drug.

Changes in the cannabinoid receptor binding, G protein coupling, and cyclic AMP cascade in the CNS of rats tolerant to and dependent on the synthetic cannabinoid compound CP55,940.

Chronic exposure to CP55,940 produced a significant down-regulation of cannabinoid receptors in the striatum, cortex, hippocampus, and cerebellum of rat brain. At 24 h after SR141716-precipitated withdrawal, we observed a tendency to return to basal levels in the striatum and cortex, whereas the specific binding remained lower in the hippocampus and cerebellum. When we surveyed cannabinoid receptor-activated G proteins, in chronic CP55,940-treated rats the guanosine 5'-O:-(3-[(35)S]thiotriphosphate) ([(35)S]GTPgammaS) binding assay revealed a decrease of activated G proteins in the striatum, cortex, and hippocampus, whereas no significant changes were seen in the cerebellum. At 24 h after the SR141716-precipitated withdrawal, [(35)S]GTPgammaS binding increased compared with that of rats chronically exposed to CP55,940, attaining the control level except for cerebellum, where we observed a trend to overcome the control amounts. Concerning the cyclic AMP (cAMP) cascade, which represents the major intracellular signaling pathway activated by cannabinoid receptors, in the cerebral areas from rats chronically exposed to CP55,940 we found alteration in neither cAMP levels nor protein kinase A activity. In the brain regions taken from CP55, 940-withdrawn rats, we only observed a significant up-regulation in the cerebellum. Our findings suggest that receptor desensitization and down-regulation are strictly involved in the development of cannabinoid tolerance, whereas alterations in the cAMP cascade in the cerebellum could be relevant in the mediation of the motor component of cannabinoid abstinence.

Long-term treatment with SR141716A, the CB1 receptor antagonist, influences morphine withdrawal syndrome.

The role of the cannabinoid system in morphine withdrawal was examined through long-term CB1 receptor antagonist administration in morphine pellet implanted rats. SR141716A chronic treatment (5mg/kg i.p. twice a day for four days) did not influence the development of tolerance to the morphine analgesic effect but significantly reduced the intensity of naloxone-induced opiate withdrawal in tolerant rats: Specifically there was a significant reduction in the number of digging, teeth chattering and penile licking and the incidence of diarrhoea while other signs such as writhing, head dog shakes and rearing were unaffected. These results suggest that the pharmacological treatment with SR141716A could be of some interest in ameliorating opiate withdrawal syndrome.