Effects of cannabidiol and Δ9-tetrahydrocannabinol in the elevated plus maze in mice.

The present study tested the effects of cannabidiol (CBD) alone, Δ-9-tetrahydrocannabinol (THC) alone, and CBD and THC in combination (15:1 ratio) in the elevated plus maze (EPM), a test useful for the study of anxiety. In dose-response studies, adult, male CD1 mice were injected intraperitoneally with (1) CBD alone (0-96 mg/kg), (2) THC alone (0-6.4 mg/kg) or (3) CBD+THC in a 15:1 combination (0.0 + 0.0 mg/kg to 96.0 + 6.4 mg/kg). Diazepam (2.5 mg/kg) was also tested as a positive control. It was found that diazepam significantly increased open arm time in the EPM. CBD alone had no significant effect at any dose or injection-test interval. THC alone, however, caused a significant increase in open arm time at 3.2 and 6.4 mg/kg - doses which did not affect locomotion as measured by closed-arm entries. The effect of the combination of CBD and THC was not significantly different than the effect of THC alone. CBD alone did not have anxiolytic-like effects. THC had anxiolytic-like effects at nontoxic doses. No interaction between THC and CBD was seen when the two were combined.

Antiseizure effects of the cannabinoids in the amygdala-kindling model.

OBJECTIVE: Focal impaired awareness seizures (FIASs) are the most common seizure type in adults and are often refractory to medication. Management of FIASs is clinically challenging, and new interventions are needed for better seizure control. The amygdala-kindling model is a preclinical model of FIASs with secondary generalization. The present study assessed the efficacy of cannabidiol (CBD), ∆9-tetrahydrocannabinol (THC), and a combination of CBD and THC in a 15:1 ratio at suppressing focal and secondarily generalized seizures in the amygdala-kindled rat. METHODS: Fully kindled, male Sprague Dawley rats, with bipolar electrodes implanted in the right amygdala, were given either CBD (0-320 mg/kg), THC (0-40 mg/kg), or a combination of CBD and THC (15:1 ratio, multiple doses) intraperitoneally. Suprathreshold kindling stimulation was administered 1 h (THC) or 2 h (CBD) after drug injection, and outcomes were assessed using focal electroencephalographic recording and the Racine seizure scale. RESULTS: CBD alone produced a partial suppression of both generalized seizures (median effective dose [ED50 ] = 283 mg/kg) and focal seizures (ED40 = 320 mg/kg) at doses that did not produce ataxia. THC alone also produced partial suppression of generalized (ED50 = 10 mg/kg) and focal (ED50 = 30 mg/kg) seizures, but doses of 10 mg/kg and above produced hypolocomotion, although not ataxia. The addition of a low dose of THC to CBD (15:1) left-shifted the CBD dose-response curve, producing much lower ED50 s for both generalized (ED50 = 26 + 1.73 mg/kg) and focal (ED50 = 40 + 2.66 mg/kg) seizures. No ataxia or hypolocomotion was seen at these doses of the CBD + THC combination. SIGNIFICANCE: CBD and THC both have antiseizure properties in the amygdala-kindling model, although THC produces suppression of the amygdala focus only at doses that produce hypolocomotion. The addition of small amounts of THC greatly improves the effectiveness of CBD. A combination of CBD and THC might be useful for the management of FIASs.

A minimum of 3 months of dietary fish oil supplementation is required to raise amygdaloid afterdischarge seizure thresholds in rats--implications for treating complex partial seizures.

Complex partial seizures, which typically originate in limbic structures such as the amygdala, are often resistant to antiseizure medications. Our goal was to investigate the effects of chronic dietary supplementation with n-3 polyunsaturated fatty acids (PUFAs) derived from fish oil on seizure thresholds in the amygdala, as well as on blood and brain PUFA levels. The acute effects of injected n-3 PUFAs--eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)--were also tested in the maximal pentylenetetrazol (PTZ) seizure model. In amygdala-implanted subjects, fish oil supplementation significantly increased amygdaloid afterdischarge thresholds, as compared with controls at 3, 5, and 7 months after the start of supplementation. Fish oil supplementation also increased serum EPA and DHA concentrations. DHA concentration in the pyriform-amygdala area increased in the fish-oil treated group by 17-34%, but this effect did not reach statistical significance (P=0.065). DHA significantly increased the latency to seizure onset in the PTZ seizure model, whereas EPA had no significant effect. These observations suggest that chronic dietary fish oil supplementation can raise focal amygdaloid seizure thresholds and that this effect is likely mediated by DHA rather than by EPA.

Automobilization intervention and exercise for temporomandibular joint open lock.

Temporomandibular joint disorders (TMDs) are common and may cause temporomandibular joint (TMJ) locking, pain, and disability. Evidence supports use of manual therapy and exercise for treatment of TMDs including disk displacement limiting full mouth opening, TMJ 'closed lock'. Only limited case studies describe management of TMJ 'open lock', a condition due to posterior disk displacement (PDD) or TMJ anterior dislocation (TMJ-AD). Reported treatment for open lock includes splinting and intraoral joint manipulation. This case report describes a novel extraoral automobilization using the mandibular elevator muscles to treat TMJ open lock in a 22-year-old male after intraoral joint mobilization failed. The exercise program used to restore neuromuscular control for post-reduction management is described. Short term results of automobilization were excellent with restored ability to swallow, speak normally, and achieve occlusion. Long term results at 14 months were good: the patient was pain-free, could swallow and speak normally, had no recurrence of TMJ locking, and minimal disability. Limited right lateral excursion range and left mandibular deviation during mouth opening indicated possible persistence of PDD. This case suggests that mandibular elevator automobilization and masticatory muscle exercise may be useful to treat TMJ open lock and should be considered to treat PDD and TMJ-AD.

Extrafocal threshold reductions in amygdala-kindled rats.

PURPOSE: Racine's classic study suggested that after discharge thresholds were reduced in the primary stimulation site (amygdala) of kindled rats, but that that they were not reduced in secondary (nonstimulated) sites. However, recent reports of neurochemical changes related to excitation and inhibition in nonstimulated sites in kindled brains would be expected to cause reductions in afterdischarge thresholds in these sites. More recently Sanei et al. have reported a significant threshold reduction in the piriform cortex of amygdala- and hippocampus-kindled cats, but not in the entorhinal cortex. The present study was designed to determine whether the results of Sanei et al. in cats could be replicated in rats kindled in the amygdala-a model commonly used in studies of seizure mechanisms and anticonvulsant drug development. METHODS: Adult, male Long-Evans rats were kindled in the amygdala or given matched handling. Beginning 48 h following the last stimulation, afterdischarge thresholds were determined in the ipsilateral piriform and entorhinal cortices. Amygdala thresholds were determined 24 h later. RESULTS: Afterdischarge thresholds were significantly reduced in both the amygdala and the ipsilateral entorhinal cortex of amygdala-kindled rats. Afterdischarge thresholds in the piriform cortex did not differ significantly between kindled and control subjects. DISCUSSION: These data suggest that threshold reduction occurs outside the primary kindling site in rats as well as in cats. Extrafocal changes in afterdischarge threshold may be functionally important, and might possibly relate to extrafocal neurochemical changes and progressive generalization of seizure discharge from discrete focal sites.

Development of propagated discharge and behavioral arrest in hippocampal and amygdala-kindled animals.

Patients with focal temporal lobe seizures often experience transient episodes of impaired awareness with behavioral arrest, but the precise mechanism remains unknown. The Network Inhibition Hypothesis attributes these deficits to a loss of cholinergic input to the cortex. This is presumed to result from increased activation of inhibitory regions that suppress subcortical arousal, giving rise to cortical delta wave activity. Recently, this hypothesis has been tested in animal experiments, where triggering dorsal hippocampal seizures is associated with behavioral arrest. To further test this hypothesis in animals - and, more specifically, to characterize the relationship between propagated discharge, cortical delta waves and behavioral arrest - we performed partial kindling studies in three different limbic sites in rats. We found that seizure discharge took longer to spread from the amygdala than the hippocampus, and took more stimulations to elicit behavioral arrest. In addition, the onset of propagated discharge in subcortical and cortical sites did not always match with the onset of behavioral arrest. Importantly, the activity seen in the cortex did not resemble the slow waves seen in deep sleep. Together, these findings suggest that limbic discharge triggers epileptic discharge in downstream pacemakers, including the cortex, and that these secondarily cause behavioral arrest.

Involvement of the neuronal phosphotyrosine signal adaptor N-Shc in kainic acid-induced epileptiform activity.

BDNF-TrkB signaling is implicated in experimental seizures and epilepsy. However, the downstream signaling involved in the epileptiform activity caused by TrkB receptor activation is still unknown. The aim of the present study was to determine whether TrkB-mediated N-Shc signal transduction was involved in kainic acid (KA)-induced epileptiform activity. We investigated KA-induced behavioral seizures, epileptiform activities and neuronal cell loss in hippocampus between N-Shc deficient and control mice. There was a significant reduction in seizure severity and the frequency of epileptiform discharges in N-Shc deficient mice, as compared with wild-type and C57BL/6 mice. KA-induced neuronal cell loss in the CA3 of hippocampus was also inhibited in N-Shc deficient mice. This study demonstrates that the activation of N-Shc signaling pathway contributes to an acute KA-induced epileptiform activity and neuronal cell loss in the hippocampus. We propose that the N-Shc-mediated signaling pathway could provide a potential target for the novel therapeutic approaches of epilepsy.

Tactile, acoustic and vestibular systems sum to elicit the startle reflex.

The startle reflex is elicited by intense tactile, acoustic or vestibular stimuli. Fast mechanoreceptors in each modality can respond to skin or head displacement. In each modality, stimulation of cranial nerves or primary sensory nuclei evokes startle-like responses. The most sensitive sites in rats are found in the ventral spinal trigeminal pathway, corresponding to inputs from the dorsal face. Cross-modal summation is stronger than intramodal temporal summation, suggesting that the convergence of acoustic, vestibular and tactile information is important for eliciting startle. This summation declines sharply if the cross-modal stimuli are not synchronous. Head impact stimuli activate trigeminal, acoustic and vestibular systems together, suggesting that the startle response protects the body from impact stimuli. In each primary sensory nucleus, large, second-order neurons project to pontine reticular formation giant neurons critical for the acoustic startle reflex. In vestibular nucleus sites, startle-like responses appear to be mediated mainly via the vestibulospinal tract, not the reticulospinal tract. Summation between vestibulospinal and reticulospinal pathways mediating startle is proposed to occur in the ventral spinal cord.

Treatment of developmental dislocation of hip: does changing the hip abduction angle in the hip spica affect the rate of avascular necrosis of the femoral head?

Avascular necrosis (AVN) of the femoral head is a serious complication in the management of developmental dislocation of the hip. Increasing the abduction angle increases its stability but compromises the vascularity of the femoral head. From our database of 240 children treated for developmental dislocation of hip by the two senior authors between 1998 and 2008, we defined two groups of children who underwent closed or medial open reduction of the hip after a failed Pavlik treatment or if patients presented late. In group 1, the reduced hip was immobilized in around 90° flexion, 60° abduction, and 0-10° internal rotation. In group 2 the hip was immobilized in around 45° of hip abduction with flexion and internal rotation as before. The first and second authors independently analysed these two groups blinded to the hip abduction angle. Our hypothesis was that a reduction in the hip abduction angle would reduce the incidence of AVN in the second group without compromising the stability. All eligible children were included, and there were 42 children in group 1 and 44 children in group 2. An almost equal number of children underwent closed and medial open reduction in both the groups. The age at reduction was a mode of 6 months (range 6-13 months) and 7 months (range 7-12 months), respectively. The abduction angle in the first group had a mode of 60° (range 52-70°) and the second group had a mode of 45° (range 38-50°). Radiographic evidence of AVN as described by Salter and colleagues was seen in eight children (19%) in the first group and seven children (16%) in the second group (P=0.78). Redislocation occurred in one child in the second group and none in the first group. In summary, the results show a nonsignificant reduction in the incidence of AVN when the hip abduction angle was reduced with no significant increased risk of redislocation.

Comparative study of five antiepileptic drugs on a translational cognitive measure in the rat: relationship to antiepileptic property.

RATIONALE: Antiepileptic drugs (AEDs) have been available for many years; yet, new members of this class continue to be identified and developed due to the limitations of existing drugs, which include a propensity for cognitive impairment. However, there is little preclinical information about the cognitive effects they produce, which clinically include deficits in attention and slowing of reaction time. OBJECTIVES: The purpose of this study was to profile two first-generation AEDs, phenytoin and valproate, and three second-generation AEDs, levetiracetam, pregabalin and lacosamide. Initially, each drug was examined across a range of well characterised preclinical seizure tests, and then each drug was evaluated in the five-choice serial reaction time test (5-CSRTT) based on efficacious doses from the seizure tests. MATERIALS AND METHODS: Each AED was tested for anti-seizure efficacy in either (1) the maximal electroshock seizure test, (2) s.c. PTZ seizure test, (3) amygdala-kindled seizures and (4) the genetic absence epilepsy rat of Strasbourg model of absence seizures. On completion of these studies, each drug was tested in rats trained to asymptotic performance in the 5-CSRTT (0.5 s SD, 5 s ITI, 100 trials). Male rats were used in all studies. RESULTS: Each AED was active in at least one of the seizure tests, although only valproate was active in each test. In the 5-CSRT test, all drugs with the exception of levetiracetam, significantly slowed reaction time and increased omissions. Variable effects were seen on accuracy. The effect on omissions was reversed by increasing stimulus duration from 0.5 to 5 s, supporting a drug-induced attention deficit. Levetiracetam had no negative effect on performance; indeed, reaction time was slightly increased (i.e. faster). CONCLUSIONS: These results highlight somewhat similar effects of phenytoin, valproate, pregabalin and lacosamide on attention and reaction time, and comparison to efficacious doses from the seizure tests support the view that there may be a better separation with the newer AEDs. Levetiracetam had no detrimental effect in the 5-CSRTT, which may be consistent with clinical experience where the drug is considered to be well tolerated amongst the AED class.