Nobuaki Egashira

Cannabidiol Prevents Cerebral Infarction Via a Serotonergic 5-Hydroxytryptamine1A Receptor–Dependent Mechanism

Background and Purpose— Cannabidiol has been reported to be a neuroprotectant, but the neuroprotective mechanism of cannabidiol remains unclear. We studied the neuroprotective mechanism of cannabidiol in 4-hour middle cerebral artery (MCA) occlusion mice. Methods— Male MCA occluded mice were treated with cannabidiol, abnormal cannabidiol, anandamide, methanandamide, cannabidiol plus capsazepine, and cannabidiol plus WAY100135 before and 3 hours after MCA occlusion. The infarct size was determined after 24 hours (2,3,5-triphenyltetrazolium chloride staining). Cerebral blood flow (CBF) was measured at, before and 1, 2, 3, and 4 hours after MCA occlusion. Results— Cannabidiol significantly reduced the infarct volume induced by MCA occlusion in a bell-shaped curve. Similarly, abnormal cannabidiol but not anandamide or methanandamide reduced the infarct volume. Moreover, the neuroprotective effect of cannabidiol was inhibited by WAY100135, a serotonin 5-hydroxytriptamine1A (5-HT1A) receptor antagonist but not capsazepine a vanilloid receptor antagonist. Cannabidiol increased CBF to the cortex, and the CBF was partly inhibited by WAY100135 in mice subjected to MCA occlusion. Conclusions— Cannabidiol and abnormal cannabidiol reduced the infarct volume. Furthermore, the neuroprotective effect of cannabidiol was inhibited by WAY100135 but not capsazepine, and the CBF increased by cannabidiol was partially reversed by WAY100135. These results suggested that the neuroprotective effect of cannabidiol may be related to the increase in CBF through the serotonergic 5-HT1A receptor.

Impaired social interaction and reduced anxiety-related behavior in vasopressin V1a receptor knockout mice

The arginine vasopressin (AVP) system plays an important role in social behavior. Autism, with its hallmark disturbances in social behavior, has been associated with the V1a receptor (V1aR) gene. Furthermore, impairments of social function are often observed in symptoms of schizophrenia. Subchronic phencyclidine (PCP) produces behaviors relating to certain aspects of schizophrenic symptoms such as impairing social interaction in animals and it reduces the density of V1aR binding sites in several brain regions. Here, we report that V1aR knockout (KO) mice exhibited impairment of social behavior in a social interaction test, and showed reduced anxiety-related behavior in elevated plus-maze and marble-burying behavior tests. Given the current findings, the V1aR may be involved in the regulation of social interaction, and V1aR KO mice could be used as an animal model of psychiatric disorders associated with social behavior deficits, such as autism and schizophrenia.

Neuroprotective effect of γ-glutamylethylamide (theanine) on cerebral infarction in mice

In the present study, we examined the neuroprotective effect of γ-glutamylethylamide (theanine) on the ischemic brain damage in a middle cerebral artery occlusion model in mice. Theanine was injected i.p. 3 h after the occlusion or immediately before and 3 h after the occlusion. Theanine (1 mg/kg) significantly decreased the size of the cerebral infarcts 1 day after the occlusion. In contrast, theanine did not affect the cerebral blood flow, brain temperature and physiological variables (pH, pCO2, pO2 and hematocrit) in this model. These results suggest that theanine directly provides neuroprotection against focal cerebral ischemia and may be clinically useful for preventing cerebral infarction.

Intracerebral microinjections of Δ9-tetrahydrocannabinol: search for the impairment of spatial memory in the eight-arm radial maze in rats

The purpose of this study was to identify brain sites that contribute to the delta(9)-tetrahydrocannabinol (delta(9)-THC)-induced impairment of spatial memory in rats. Rats were tested in the eight-arm radial maze after microinjections of delta(9)-THC into one of 14 different brain regions. The bilateral microinjection of delta(9)-THC (20 microg/side) impaired spatial memory when injected into the dorsal hippocampus (DH), ventral hippocampus (VH) or dorsomedial thalamus nucleus (DMT). However, rats treated with delta(9)-THC into DMT produced preseverative behavior which has not been observed by systemic administration of delta(9)-THC. On the other hand, spatial memory was unaffected by microinjections of delta(9)-THC into the other 11 areas examined: frontal (FC) and frontoparietal (FPC) cortex, central (ACE) and basolateral (ABL) amygdaloid nucleus, medial caudate putamen (CPM), lateral hypothalamus (LH), mammillary body (MB), basal forebrain (BF), medial septal nucleus (SEP) and dorsal (DR) and median (MR) raphe nucleus. These results suggest that DH and VH may be important brain sites for the delta(9)-THC-induced impairment of spatial memory.

Vitamin E isoforms α-tocotrienol and γ-tocopherol prevent cerebral infarction in mice

Abstract α-tocopherol and its derivatives have been shown to be effective in reducing cerebral ischemia-induced brain damage. However, the effects of other vitamin E isoforms have not been characterized. In the present study, we investigated the effects of six different isoforms of vitamin E on the ischemic brain damage in the mice middle cerebral artery (MCA) occlusion model. All vitamin E isoforms were injected i.v., twice, immediately before and 3 h after the occlusion. α-tocopherol (2 mM), α-tocotrienol (0.2 and 2 mM) and γ-tocopherol (0.2 and 2 mM) significantly decreased the size of the cerebral infarcts 1 day after the MCA occlusion, while γ-tocotrienol, δ-tocopherol and δ-tocotrienol showed no effect on the cerebral infarcts. These results suggest that α-tocotrienol and γ-tocopherol are potent and effective agents for preventing cerebral infarction induced by MCA occlusion.

Cannabidiol potentiates pharmacological effects of Δ9-tetrahydrocannabinol via CB1 receptor-dependent mechanism

Cannabidiol, a non-psychoactive component of cannabis, has been reported to have interactions with Delta(9)-tetrahydrocannabinol (Delta(9)-THC). However, such interactions have not sufficiently been clear and may have important implications for understanding the pharmacological effects of marijuana. In the present study, we investigated whether cannabidiol modulates the pharmacological effects of Delta(9)-THC on locomotor activity, catalepsy-like immobilisation, rectal temperature and spatial memory in the eight-arm radial maze task in mice. In addition, we measured expression level of cannabinoid CB(1) receptor at striatum, cortex, hippocampus and hypothalamus. Delta(9)-THC (1, 3, 6 and 10 mg/kg) induced hypoactivity, catalepsy-like immobilisation and hypothermia in a dose-dependent manner. In addition, Delta(9)-THC (1, 3 and 6 mg/kg) dose-dependently impaired spatial memory in eight-arm radial maze. On the other hand, cannabidiol (1, 3, 10, 25 and 50 mg/kg) did not affect locomotor activity, catalepsy-like immobilisation, rectal temperature and spatial memory on its own. However, higher dose of cannabidiol (10 or 50 mg/kg) exacerbated pharmacological effects of lower dose of Delta(9)-THC, such as hypoactivity, hypothermia and impairment of spatial memory. Moreover, cannabidiol (50 mg/kg) with Delta(9)-THC (1 mg/kg) enhanced the expression level of CB(1) receptor expression in hippocampus and hypothalamus. Cannabidiol potentiated pharmacological effects of Delta(9)-THC via CB(1) receptor-dependent mechanism. These findings may contribute in setting the basis for interaction of cannabinoids and to find a cannabinoid mechanism in central nervous system.

Involvement of 5-hydroxytryptamine neuronal system in Δ9-tetrahydrocannabinol-induced impairment of spatial memory

The present study investigated the involvement of the serotonin (5-hydroxytryptamine, 5-HT) neuronal system in the Delta(9)-tetrahydrocannabinol-induced impairment of spatial memory in the eight-arm radial maze in rats. Delta(9)-Tetrahydrocannabinol (6 mg/kg, i.p.), which impairs spatial memory, significantly increased the 5-HT content in the ventral hippocampus. A microdialysis study showed that Delta(9)-tetrahydrocannabinol (6 mg/kg, i.p.) decreased 5-HT release in the ventral hippocampus. The 5-HT precursor, 5-hydroxy-L-tryptophan (5-HTP; 50 mg/kg, i.p.), the 5-HT re-uptake inhibitor, clomipramine (0.01 and 0.1 mg/kg, i.p.), the 5-HT receptor agonist, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT; 0.01 and 0.03 mg/kg, i.p.), and the 5-HT(2) receptor agonist, 1-(2,5-dimethoxy 4-iodophenyl)-2-amino propane (DOI; 10 microg/kg, i.p.), significantly attenuated the Delta(9)-tetrahydrocannabinol-induced impairment of spatial memory. These results suggest that the 5-HT neuronal system may be involved in the Delta(9)-tetrahydrocannabinol-induced impairment of spatial memory.

V1a receptor knockout mice exhibit impairment of spatial memory in an eight-arm radial maze

In this study, we examined the performance of vasopressin V1a receptor (V1aR) and vasopressin V1b receptor (V1bR) knockout (KO) mice compared to wild-type (WT) mice in an eight-arm radial maze. V1aR KO mice exhibited an impairment of spatial memory in comparison to WT mice. By contrast, we did not observe any significant differences between the V1bR KO mice and the WT mice in the eight-arm radial maze. Moreover, OPC-21268, a selective V1aR antagonist, impaired spatial memory in the eight-arm radial maze in WT mice characterized by an increased number of errors. These results suggest that the V1aR controls spatial memory in mice.

Antipsychotics improve Δ9-tetrahydrocannabinol-induced impairment of the prepulse inhibition of the startle reflex in mice

Recently, cannabinoid receptor agonists have been reported to impair prepulse inhibition (PPI) of the startle reflex. In the current study, we examined the effect of Delta9-tetrahydrocannabinol (THC), the principal psychoactive component of cannabis, on the PPI, and found that THC (10 mg/kg, i.p.) impaired the PPI concomitant with a decrease in the startle response. Antipsychotics such as haloperidol (0.3 mg/kg, i.p.) and risperidone (0.1 mg/kg, i.p.), which are potent dopamine D2 receptor antagonists, and SR141716 (10 mg/kg, i.p.), a CB1 cannabinoid receptor antagonist, reversed these THC-induced PPI deficits. Moreover, THC (10 mg/kg) increased dopamine (DA) release in the nucleus accumbens but not medial prefrontal cortex over a 50-100-min period (time of PPI test) after treatment, and SR141716 (10 mg/kg) reversed this increase in DA release induced by THC. These results suggest that dopaminergic hyperfunction in the nucleus accumbens may be involved in THC-induced PPI deficits.

Cannabidiol prevents a post-ischemic injury progressively induced by cerebral ischemia via a high-mobility group box1-inhibiting mechanism.

We examined the cerebroprotective mechanism of cannabidiol, the non-psychoactive component of marijuana, against infarction in a 4-h mouse middle cerebral artery (MCA) occlusion model. Cannabidiol was intraperitoneally administrated immediately before and 3h after cerebral ischemia. Infarct size and myeloperoxidase (MPO) activity, a marker of neutrophil, monocyte/macropharge, were measured at 24h after cerebral ischemia. Activated microglia and astrocytes were evaluated by immunostaining. Moreover, high-mobility group box1 (HMGB1) was also evaluated at 1 and 3 days after MCA occlusion. In addition, neurological score and motor coordination on the rota-rod test were assessed at 1 and 3 days after cerebral ischemia. Cannabidiol significantly prevented infarction and MPO activity at 20h after reperfusion. These effects of cannabidiol were not inhibited by either SR141716 or AM630. Cannabidiol inhibited the MPO-positive cells expressing HMGB1 and also decreased the expression level of HMGB1 in plasma. In addition, cannabidiol decreased the number of Iba1- and GFAP-positive cells at 3 days after cerebral ischemia. Moreover, cannabidiol improved neurological score and motor coordination on the rota-rod test. Our results suggest that cannabidiol inhibits monocyte/macropharge expressing HMGB1 followed by preventing glial activation and neurological impairment induced by cerebral ischemia. Cannabidiol will open new therapeutic possibilities for post-ischemic injury via HMGB1-inhibiting mechanism.