Immunohistochemical characterisation and localisation of cannabinoid CB1 receptor protein in the rat vestibular nucleus complex and the effects of unilateral vestibular deafferentation

Potential effects of cannabinoids on audiovestibular function: A narrative review

The growing interest in the development of drugs that target the endocannabinoid system has extended to conditions that affect the audiovestibular pathway. The expression of cannabinoid (CB) receptors in that pathway has been widely demonstrated, indicating a therapeutic potential for drug development at this level. These medications may be beneficial for conditions such as noise-induced hearing loss, ototoxicity, or various forms of vertigo of central or peripheral origin. The therapeutic targets of interest include natural or synthetic compounds that act as CB1/CB2 receptor agonists/antagonists, and inhibitors of the endocannabinoid-degrading enzymes FAAH and MAGL. Furthermore, genetic variations implicated in the response to treatment and the development of related disorders such as epilepsy or migraine have been identified. Direct methods of administering these medications should be examined beyond the systemic strategy.

The cannabinoid receptors system in horses: Tissue distribution and cellular identification in skin

BACKGROUND

The endocannabinoid system (ECS) is composed of cannabinoid receptors type 1 (CBR1) and type 2 (CBR2), cannabinoid-based ligands (endogenous chemically synthesized phytocannabinoids), and endogenous enzymes controlling their concentrations. Cannabinoid receptors (CBRs) have been identified in invertebrates and in almost all vertebrate species in the central and peripheral nervous system as well as in immune cells, where they control neuroimmune homeostasis. In humans, rodents, dogs, and cats, CBRs expression has been confirmed in the skin, and their expression and tissue distribution become disordered in pathological conditions. Cannabinoid receptors may be a possible therapeutic target in skin diseases.

OBJECTIVES

To characterize the distribution and cellular expression of CBRs in the skin of horses under normal conditions.

ANIMALS

Fifteen healthy horses.

METHODS

Using full-thickness skin punch biopsy samples, skin-derived primary epidermal keratinocytes and dermal-derived cells, we performed analysis of Cnr1 and Cnr2 genes using real-time PCR and CBR1 and CBR2 protein expression by confocal microscopy and Western blotting.

RESULTS

Normal equine skin, including equine epidermal keratinocytes and dermal fibroblast-like cells, all exhibited constant gene and protein expression of CBRs.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results represent a starting point for developing and translating new veterinary medicine-based pharmacotherapies using ECS as a possible target.

Cannabinoids in Neurology - Position paper from Scientific Departments from Brazilian Academy of Neurology

Cannabinoids comprehend endocannabinoids, phytocannabinoids, and synthetic cannabinoids, with actions both in the central and peripherical nervous systems. A considerable amount of publications have been made in recent years, although cannabis has been known for over a thousand years. Scientific Departments from the Brazilian Academy of Neurology described evidence for medical use in their areas. Literature is constantly changing, and possible new evidence can emerge in the next days or months. Prescription of these substances must be discussed with patients and their families, with knowledge about adverse events and their efficacy.

Adverse events following cannabis for medical use in Tuscany: An analysis of the Italian Phytovigilance database

AIMS

Despite a significant increase in using cannabis for medical purposes, current evidence on its safety in real-world clinical practice is still poorly characterised. By a case-by-case analysis of spontaneous reports of suspected adverse events (AEs) collected in Tuscany within the Italian Phytovigilance database, the aim of the present study was to describe AEs occurred in patients exposed to medical cannabis.

METHODS

We evaluated all reports of cannabis-related suspected AEs collected within the Phytovigilance database up to December 2018. Information regarding cannabis therapy, patient's demographic and clinical characteristics, concomitant medications, AE description according to the Medical Dictionary for Regulatory Activities (MedDRA) classification, AE seriousness and AE outcome, were collected. The causality assessment was performed following World Health Organisation-Uppsala Monitoring Centre criteria.

RESULTS

Fifty-three cannabis-related AE reports were analysed. The majority of patients were females (77.3%), with a mean age of 61.9 years. Thirty-nine (73.6%) cases were defined as nonserious and the majority of them (86.9%) showed a complete resolution or improvement. Forty-six (86.8%) cases were judged as probably related to cannabis consumption. The most frequently reported system organ class was psychiatric and nervous system disorders, and a potential drug-drug interaction was present in 16 cases.

CONCLUSION

Cannabis was generally well tolerated and the majority of AEs were mild and transient. Our analysis highlighted important safety issues for clinical practice, in particular the need for an accurate prescription monitoring during the titration phase, particularly in the presence of concomitant medications.

Cannabinoids, cannabinoid receptors and tinnitus

One hypothesis suggests that tinnitus is a form of sensory epilepsy, arising partly from neuronal hyperactivity in auditory regions of the brain such as the cochlear nucleus and inferior colliculus. Although there is currently no effective drug treatment for tinnitus, anti-epileptic drugs are used in some cases as a potential treatment option. There is increasing evidence to suggest that cannabinoid drugs, i.e. cannabinoid receptor agonists, can also have anti-epileptic effects, at least in some cases and in some parts of the brain. It has been reported that cannabinoid CB1 receptors and the endogenous cannabinoid, 2-arachidonylglycerol (2-AG), are expressed in the cochlear nucleus and that they are involved in the regulation of plasticity. This review explores the question of whether cannabinoid receptor agonists are likely to be pro- or anti-epileptic in the cochlear nucleus and therefore whether cannabinoids and Cannabis itself are likely to make tinnitus better or worse.

Restoration of descending inputs fails to rescue activity following deafferentation of a motor network

Motor networks such as the pyloric network of the stomatogastric ganglion often require descending neuromodulatory inputs to initiate, regulate, and modulate their activity and their synaptic connectivity to manifest physiologically appropriate output. Prolonged removal of these descending inputs often results in a compensatory response that alters the inputs themselves, their targets, or both. Using the pyloric network of the crab, Cancer borealis, we investigated whether isolation of motor networks would result in alterations that change the responses of these networks to restored modulatory input. We used a reversible block with isotonic sucrose to transiently alter descending inputs into the pyloric network of the crab stomatogastric ganglion. Using this method, we found that blocking neuromodulatory inputs caused a reduced ability for subsequently restored modulatory projections to appropriately generate network output. Our results suggest that this could be due to changes in activity of descending projection neurons as well as changes in sensitivity to neuromodulators of the target neurons that develop over the time course of the blockade. These findings suggest that although homeostatic plasticity may play a critical role in recovery of functional output in a deafferented motor network, the results of these compensatory changes may alter the network such that restored inputs no longer function appropriately.

Cannabinoid CB(1) receptor expression and affinity in the rat hippocampus following bilateral vestibular deafferentation

Numerous studies have shown that bilateral vestibular deafferentation (BVD) results in spatial memory deficits and hippocampal dysfunction in rats and humans. Since cannabinoid CB(1) receptors are well known to regulate synaptic plasticity in the hippocampus, we investigated whether BVD resulted in changes in CB(1) receptor expression and affinity in the rat hippocampus at 1, 3 and 7 days post-surgery, using a combination of Western blotting and radioligand binding. Using Western blotting, we found that CB(1) receptor expression was significantly lower in BVD animals compared to sham controls only in the CA3 area across the 3 time points (P=0.03). CB(1) receptor expression decreased significantly over time for both the BVD and sham animals (P=0.000). The radioligand binding assays showed no significant change in the IC(50) of the CB(1) receptor for the cannabinoid CB(1)/CB(2) receptor agonist, WIN55,212-2. These results suggest that the CB(1) receptor down-regulates in the CA3 region of the hippocampus following BVD, but with no changes in the affinity of the CB(1) receptor for WIN55,212-2.

Move it or lose it--is stimulation of the vestibular system necessary for normal spatial memory?

Studies in both experimental animals and human patients have demonstrated that peripheral vestibular lesions, especially bilateral lesions, are associated with spatial memory impairment that is long-lasting and may even be permanent. Electrophysiological evidence from animals indicates that bilateral vestibular loss causes place cells and theta activity to become dysfunctional; the most recent human evidence suggests that the hippocampus may cause atrophy in patients with bilateral vestibular lesions. Taken together, these studies suggest that self-motion information provided by the vestibular system is important for the development of spatial memory by areas of the brain such as the hippocampus, and when it is lost, spatial memory is impaired. This naturally suggests the converse possibility that activation of the vestibular system may enhance memory. Surprisingly, there is some human evidence that this may be the case. This review considers the relationship between the vestibular system and memory and suggests that the evolutionary age of this primitive sensory system as well as how it detects self-motion (i.e., detection of acceleration vs. velocity) may be the reasons for its unique contribution to spatial memory.

New approaches in the management of spasticity in multiple sclerosis patients: role of cannabinoids

Cannabinoids such as Cannabis-based medicinal extracts (CBMEs) are increasingly being used in the treatment of spasticity associated with multiple sclerosis (MS). They have been shown to have a beneficial effect on spasticity; however, this evidence is largely based on subjective rating scales. Objective measurements using the Ashworth scale have tended to show no significant effect; however, the validity of this scale has been questioned. The available clinical trial data suggest that the adverse side effects associated with using CBMEs are generally mild, such as dry mouth, dizziness, somnolence, nausea and intoxication. However, most of these trials were run over a period of months and it is possible that other adverse side effects could develop with long-term use. There may be reason to be concerned about the use of therapeutic cannabinoids by adolescents, people predisposed to psychosis and pregnant women.

Balance before reason in rats and humans

Considerable clinical and experimental evidence indicates that loss of vestibular function results in cognitive deficits, especially deficits in spatial memory. These studies demonstrate the importance of balance for the most fundamental of cognitive processes and suggest that information about head acceleration and orientation must have been critical to the evolution of brain structures such as the hippocampus. Studies of animals with bilateral vestibular lesions have shown that theta rhythm and the activity of hippocampal place cells are severely disrupted; recent human studies show that bilateral vestibular loss is even associated with hippocampal atrophy. While it is conceivable that the effects of vestibular lesions on the hippocampus are due to chronic stress and increased glucocorticoid levels, at present there is little evidence to support this hypothesis. It is also possible that the hippocampal changes are due to a reduction in exploration and active behavior; however, in rats, at least, bilateral vestibular lesions cause hyperactivity rather than hypoactivity. Alternatively, the hippocampus may have developed a special dependence upon the vestibular system during evolution, since it was the first sensory system to reliably indicate gravitational vertical.

The effects of cannabidiol and tetrahydrocannabinol on motion-induced emesis in Suncus murinus

The effect of cannabinoids on motion-induced emesis is unknown. The present study investigated the action of phytocannabinoids against motion-induced emesis in Suncus murinus. Suncus murinus were injected intraperitoneally with either cannabidiol (CBD) (0.5, 1, 2, 5, 10, 20 and 40 mg/kg), Delta(9)-tetrahydrocannabinol (Delta(9)-THC; 0.5, 3, 5 and 10 mg/kg) or vehicle 45 min. before exposure to a 10-min. horizontal motion stimulus (amplitude 40 mm, frequency 1 Hz). In further investigations, the CB(1) receptor antagonist, N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM 251; 5 mg/kg), was injected 15 min. prior to an injection of Delta(9)-THC (3 mg/kg). The motion stimulus was applied 45 min. later. The number of emetic episodes and latency of onset to the first emetic episode were recorded. Pre-treatment with the above doses of CBD did not modify the emetic response to the motion stimulus as compared to the vehicle-treated controls. Application of the higher doses of Delta(9)-THC induced emesis in its own right, which was inhibited by AM 251. Furthermore, pre-treatment with Delta(9)-THC dose-dependently attenuated motion-induced emesis, an effect that was inhibited by AM 251. AM 251 neither induced an emetic response nor modified motion-induced emesis. The present study indicates that Delta(9)-THC, acting via the CB(1) receptors, is anti-emetic to motion, and that CBD has no effect on motion-induced emesis in Suncus murinus.

Localization of CB1 cannabinoid receptor mRNA in the brain of the chick (Gallus domesticus)

The cannabinoid receptor one (CB1) is prevalent in the brains of many species. Receptor binding, in situ hybridization and immunohistochemical surveys have described the distribution of this receptor in a limited number of species. The current study used in situ hybridization to examine the expression of CB1 mRNA in the chick brain, a non-mammalian vertebrate. The results were compared to the observed patterns of expression for CB1 mRNA, protein, and agonist binding that have been reported for other avian species and mammals. Importantly, since CB1 receptors are typically located on neuronal terminals, comparison of the somatic mRNA expression with previously reported descriptions of the location of functional receptors, allows speculation about the circuits that make use of these receptors. The expression pattern for CB1 mRNA appears to be highly conserved across species in key areas such as the cerebellum and portions of the forebrain. For example, high levels of expression were observed in the avian amygdala and hippocampus, areas which express high levels of CB1 in mammals. The avian substantia nigra and ventral tegmental area, however, showed specific labeling. This finding is in stark contrast to the high levels of receptor binding or CB1 protein, but not CB1 mRNA in these areas of the mammalian brain. Moderate labeling was also seen throughout the hyperpallium and mesopallium. Throughout the brain, a number of regions that are known to be involved in visual processing displayed high levels of expression. For example, the tectum also had strong mRNA expression within layers 9-11 of the stratum griseum et fibrosum superficale and stratum album centrale.

Cannabinoid CB2 receptor expression in the rat brainstem cochlear and vestibular nuclei

CONCLUSION

This evidence suggests that both CB1 and CB2 receptors are important in the control of balance and hearing.

OBJECTIVE

Although the cannabinoid CB1 receptor has been identified in the brainstem vestibular and cochlear nuclei, the existence of the second cannabinoid receptor subtype, the CB2 receptor, has been more controversial. The aim of this study was to determine whether or not CB2 receptors are expressed in the vestibular and cochlear nuclei.

MATERIALS AND METHODS

Data were obtained from four young male Wistar rats In analyzing the presence of CB2 receptors in the vestibular and cochlear nuclei, the immunohistochemical complex was visualized by exposure to diaminobenzidine for 20 min. Positive immunoreactivity to CB2 was expressed as brown staining in the cytoplasm, nucleus, nuclear membrane and cell membrane.

RESULTS

We confirmed the existence of the CB2 receptor in the vestibular and cochlear nuclei in the brainstem of Wistar rats.

Retinal removal up-regulates cannabinoid CB(1) receptors in the chick optic tectum

The endocannabinoid system has been implicated in several neurobiological processes, including neurodegeneration and neuroprotection. The aim of this study was to evaluate the effects of unilateral retinal ablation on the expression of the cannabinoid receptor subtype 1 (CB(1)) at both protein and mRNA levels in the optic tectum of the adult chick brain. After different survival times postlesion (2-30 days), the chick brains were subjected to immunohistochemical, immunoblotting, and real-time PCR procedures to evaluate CB(1) expression. TUNEL and Fluoro-Jade B were used to verify the possible occurrence of cell death, and immunostaining for the microtubule-associated protein MAP-2 was performed to verify possible dendritic remodeling after lesions. No cell death could be observed in the deafferented tectum, at least up to 30 days postlesion, although Fluoro-Jade B could reveal degenerating axons and terminals. Retinal ablation seems to generate an increase of CB(1) protein in the optic tectum and other retinorecipient visual areas, which paralleled an increase in MAP-2 staining. On the other hand, CB(1) mRNA levels were not changed after retinal ablation. Our results reveal that CB(1) expression in visual structures of the adult chick brain may be negatively regulated by the retinal innervation. The increase of CB(1) receptor expression observed after retinal removal indicates that these receptors are not presynaptic in retinal axons projecting to the tectum and suggests a role of the cannabinoid system in plasticity processes ensuing after lesions.

Presence of functional cannabinoid receptors in human endocrine pancreas

AIMS/HYPOTHESIS

We examined the presence of functional cannabinoid receptors 1 and 2 (CB1, CB2) in isolated human islets, phenotyped the cells producing cannabinoid receptors and analysed the actions of selective cannabinoid receptor agonists on insulin, glucagon and somatostatin secretion in vitro. We also described the localisation on islet cells of: (1) the endocannabinoid-producing enzymes N-acyl-phosphatidyl ethanolamine-hydrolysing phospholipase D and diacylglycerol lipase; and (2) the endocannabinoid-degrading enzymes fatty acid amidohydrolase and monoacyl glycerol lipase.

METHODS

Real-time PCR, western blotting and immunocytochemistry were used to analyse the presence of endocannabinoid-related proteins and genes. Static secretion experiments were used to examine the effects of activating CB1 or CB2 on insulin, glucagon and somatostatin secretion and to measure changes in 2-arachidonoylglycerol (2-AG) levels within islets. Analyses were performed in isolated human islets and in paraffin-embedded sections of human pancreas.

RESULTS

Human islets of Langerhans expressed CB1 and CB2 (also known as CNR1 and CNR2) mRNA and CB1 and CB2 proteins, and also the machinery involved in synthesis and degradation of 2-AG (the most abundant endocannabinoid, levels of which were modulated by glucose). Immunofluorescence revealed that CB1 was densely located in glucagon-secreting alpha cells and less so in insulin-secreting beta cells. CB2 was densely present in somatostatin-secreting delta cells, but absent in alpha and beta cells. In vitro experiments revealed that CB1 stimulation enhanced insulin and glucagon secretion, while CB2 agonism lowered glucose-dependent insulin secretion, showing these cannabinoid receptors to be functional.

CONCLUSIONS/INTERPRETATION

Together, these results suggest a role for endogenous endocannabinoid signalling in regulation of endocrine secretion in the human pancreas.

Inhibition of 2-arachidonoylglycerol catabolism modulates vasoconstriction of rat middle cerebral artery by the thromboxane mimetic, U-46619

BACKGROUND AND PURPOSE

Cerebrovascular smooth muscle cells express the CB1 cannabinoid receptor and CB1 agonists produce vasodilatation of the middle cerebral artery (MCA). The thromboxane A2 mimetic, U-46619, increased the content of the endocannabinoid, 2-arachidonoylglycerol (2-AG) in the MCA and 2-AG moderated the vasoconstriction produced by U46619 in this tissue. The purposes of this study were to examine the extent to which 2-AG is catabolized by cerebral arteries and to determine whether blockade of 2-AG inactivation potentiates its feedback inhibition of U-44619-mediated vasoconstriction.

EXPERIMENTAL APPROACH

The diameters of isolated, perfused MCA from male rats were measured using videomicroscopy.

KEY RESULTS

Exogenous 2-AG produces a CB1 receptor-dependent and concentration-related increase in the diameter of MCA constricted with 5-HT. The E (max) for 2-AG dilation is increased 4-fold in the presence of the metabolic inhibitors 3-(decylthio)-1,1,1-trifluropropan-2-one (DETFP), URB754 and URB597. To examine the role of catabolism in the effects of endogenous 2-AG, vasoconstriction induced by U-46619 was studied. DETFP and URB754, but not the fatty acid amide hydrolase inhibitor, URB597, significantly increased the EC(50) for U-46619. These data support a physiological role for endocannabinoid feedback inhibition in the effects of U-46619 and indicate that endogenously produced 2-AG is also efficiently catabolized within the MCA.

CONCLUSIONS AND IMPLICATIONS

MCA express mechanisms for the efficient inactivation of 2-AG, providing further support for an endocannabinoid feedback mechanism that opposes thromboxane-mediated vasoconstriction. These data suggest that potentiation of endogenously produced 2-AG could be a novel therapeutic approach to the treatment of thrombotic stroke.

Cannabinoid receptor down-regulation in the ventral cochlear nucleus in a salicylate model of tinnitus

Cannabinoid CB1 receptors have not been systematically investigated in the brainstem cochlear nucleus, nor have they been investigated in relation to tinnitus. Using immunohistochemistry and cell counting, we showed that a large number of neurons in the rat cochlear nucleus possess cannabinoid CB1 receptors. Following salicylate injections that induced the behavioural manifestations of tinnitus, the number of principal neurons in the ventral cochlear nucleus expressing CB1 receptors significantly decreased, while the number of CB1-positive principal neurons in the dorsal cochlear nucleus did not change significantly. These results suggest that CB1 receptors in the cochlear nucleus may be important for auditory function and that a down-regulation of CB1 receptors in the ventral cochlear nucleus may be related to the development of tinnitus.

The endocannabinoid system: A new player in the neurochemical control of vestibular function?

The results of recent clinical trials of medicinal cannabinoid drugs show that dizziness and vertigo are commonly reported adverse side-effects. Cannabinoid CB1 receptors were initially thought to be expressed in very low densities in the vestibular nucleus complex (VNC). Recent immunohistochemical studies have challenged this idea and suggested that CB1 receptors may exist in numbers similar to the granule cell layer of the cerebellum. This, together with evidence that brainstem CB1 receptors have a higher efficacy than those in many other parts of the brain and that application of cannabinoids can elicit potent electrophysiological effects in VNC neurons, suggests that CB1 receptors and their endogenous ligands may be important in central vestibular function. In this review, we consider the potential clinical significance of the endocannabinoid system for the development of vestibular disorders, the effects of recreational cannabis use and the therapeutic use of medicinal cannabinoids.

Characterization of CB1 cannabinoid receptor immunoreactivity in postmortem human brain homogenates

The CB1 cannabinoid receptor (CB1) is the predominant type of cannabinoid receptor in the CNS, in which it displays a unique anatomical distribution and is present at higher densities than most other known seven transmembrane domain receptors. Nevertheless, as with almost all seven transmembrane domain receptors, the tertiary and quaternary structure of this receptor is still unknown. Studies of CB1 in rat cerebral tissue are scarce, and even less is known regarding the expression of CB1 in the human brain. Thus, the aim of the present work was to characterize CB1 expression in membranes from postmortem human brain using specific antisera raised against this protein. Western blot analysis of P1 and P2 fractions, and crude plasma membrane preparations from the prefrontal cortex showed that CB1 migrated as a 60 kDa monomer under reducing conditions. These data were confirmed by blotting experiments carried out with human U373MG astrocytoma cells as a positive control for CB1 expression and wild-type CHO cells as negative control. In addition, when proteins were solubilized in the absence of dithiothreitol, the anti-human CB1 antiserum detected a new band migrating at around 120 kDa corresponding in size to a putative CB1 dimer. This band was sensitive to reducing agents (50 mM dithiothreitol) and showed sodium dodecylsulphate stability, suggesting the existence of disulfide-linked CB1 dimers in the membrane preparations. Important differences in the anatomical distribution of CB1 were observed with regard to that described previously in monkey and rat; in the human brain, CB1 levels were higher in cortex and caudate than in the cerebellum.

Expression of the cannabinoid CB2 receptor in the rat cerebellum: an immunohistochemical study

Reports of cannabinoid CB2 receptor protein in the brain have been ambiguous. We therefore tested for CB2 immunoreactivity in the rat brain using immunofluorescence. We detected CB2 labeling in fine fibers in the granule layer. This CB2 labeling did not co-localise with the astrocyte marker glial fibrillary acidic protein (GFAP) and, therefore, the CB2-positive fibers were not astrocytes and were possibly microglial or neuronal. Additionally, strong CB2 labeling was detected in capillary endothelia in the granule, Purkinje cell, and molecular layers. Our results suggest that the role of CB2 receptors in the brain may have been previously underestimated.

Mitochondrial ultrastructure and apoptotic protein expression in the vestibular nucleus complex following unilateral labyrinthectomy

We hypothesized that peripheral vestibular disorders might affect mitochondria in the vestibular nucleus complex (VNC). We tested this using unilateral labyrinthectomy (UL) as a model for the effects of vestibular damage on the VNC and used Western blotting and electron microscopy to analyze mitochondria. In rats receiving UL we did not find any changes in mitochondrial ultrastructure in the medial vestibular nucleus following UL, and there was no change in the expression or activation of the apoptosis effector caspase-3 in the whole VNC following UL. However, we did detect a small but statistically significant upregulation of the anti-apoptotic protein Bcl-2 in the contralateral VNC at 10 h post-UL.

The safety of cannabinoids for the treatment of multiple sclerosis

The evidence for the therapeutic efficacy of cannabinoids in the treatment of multiple sclerosis (MS) is increasing but is not as yet convincing. Although several trials have reported no significant effect, the majority of the evidence which supports a beneficial effect on spasticity and pain is based on subjective measurements in trials where unblinding was likely to be a problem. The available clinical trial data suggest that the adverse side effects associated with using cannabis-based medicinal extracts (CBMEs) are generally mild, such as dry mouth, dizziness, somnolence, nausea and intoxication, and in no case did toxicity develop. However, most of these trials were run over a period of months and it is possible that other adverse side effects, not seen in these short-term studies, could develop with long-term use. Despite the evidence that cannabinoids can disrupt cognitive function and promote depression, on the basis of current data, such adverse effects seem unlikely to be associated with the use of CBMEs. Likewise, there is no evidence to suggest that their effects on balance and motor control, or immune function, may be clinically significant. There is, however, reason to be concerned about the use of therapeutic cannabinoids by people predisposed to psychosis and by pregnant women, given the increasing evidence of their adverse effects on the fetus. In conclusion, given the modest therapeutic effects of cannabinoids demonstrated so far, and the risk of long-term adverse side effects, there is reason to be cautious about their use in the treatment of MS.

Cytosolic glucocorticoid receptor expression in the rat vestibular nucleus and hippocampus following unilateral vestibular deafferentation

It has been suggested that vestibular compensation, the process of behavioural recovery that occurs following peripheral vestibular damage, might be partially dependent on the release of glucocorticoids (GC) during the early stages of recovery from the lesion. One possibility is that glucocorticoid receptors (GRs) in the vestibular nucleus complex (VNC) might change following the lesion, altering their response to GCs. We sought to test this hypothesis by quantifying the expression of cytosolic GRs in the bilateral VNCs at 10 h, 58 h and 2 weeks following unilateral vestibular deafferentation (UVD) in rat, using western blotting. We also examined GR expression in the CA1, CA2/3 and dentate gyrus (DG) subregions of the hippocampus and measured serum corticosterone levels. Compared with sham surgery and anaesthetic controls, we found no significant changes in GR expression in the ipsilateral or contralateral VNCs at any time post-UVD. However, we did find a significant decrease in GR expression in the ipsilateral CA1 at 2 weeks post-UVD. Serum corticosterone levels were significantly lower in all groups at 58 h post-op. compared to 10 h and 2 weeks; however, there were no significant differences between the UVD and control groups at any time point. These results suggest that changes in GR expression in the VNC are unlikely to contribute to the development of vestibular compensation. However, long-term changes in GR expression in CA1 might be related to chronic deficits in hippocampal function and spatial cognition following vestibular damage.