Marijuana (Cannabis sativa) is the most widely used illicit drug in many western countries and has long been recognized as a centrally acting cannabinoid with wide spread effects on motor and cognitive functions. To date, two types of cannabinoid receptor (Cb) have been cloned, central type (Cb1) and peripheral type (Cb2). To better understand the potential effects of cannabis on the mature and developing human brain, we characterized the expression of Cb1 mRNA in normal adult and fetal brain sections. In situ hybridisation histochemistry was used to study the mRNA distribution on human brain cryosections. In adult brains, Cb1 mRNA was highly expressed throughout in the neocortex predominantly in layer II/III. The Cb1 mRNA expression was evident in scattered cells throughout the amygdala. In the striatum, homogenous high Cb1 mRNA was also expressed in the caudate and putamen with no patch/matrix compartmentalization pattern. Weak to moderate expression was observed in other regions, e.g., the mediodorsal t...

Tau pathology is associated with the development of such neurodegenerative diseases as Fronto-temporal Dementia with Parkinsonism linked to Chromosome 17 (FTDP-17), Progressive Supranuclear Palsy (PSP)and Cortico-Basal Degeneration (CBD). Exon 10 (E10) of Tau encodes one of four imperfect repeat microtubule binding domains. It is alternatively spliced in the adult human brain, creating proteins with either three (3R) or four (4) repeats. Mutations associated with FTDP-17 close to the 5'-slice site of E10 have been shown to increase the inclusion of E10 in tau mRNA, and therefore 4R Tau protein. We constructed a minigene incorporating E9 and E11 with ~100bp of flanking intronic sequence, and E10 with ~1kb of intronic sequence flanking E10. We show that the minigene the ratio of E10+.E10- closely approximates that seen in human brain when expressed in neuronal, but not non-neuronal cell lines. Mutations known to cause FTDP-17 through alterations in splicing of E10 in vivo are shown to affect the splicing of ...

Alternative splicing of the human P/Q-type (α1A) channel provides a potentially rich source of functional diversity. Here, exon scanning of the human α1A gene revealed the presence of 9 loci in which the alternative use of junctional splice sites or exons produces different splice variants. Four alternative splice sites in the carboxyl tail, at exons 37, 43, 44 and 47, are particularly intriguing, because of their proximity to a reputed calmodulin binding domain (CBD) in exon 42 (Lee et al, Nature 399:155), which may support Ca2+-dependent inactivation and facilitation of P/Q-type channels. Interestingly, all permutations of the presence or absence of adjacent exons 43/44 (++, +-, -+, and --) were detected in human cerebellar cDNAs. We therefore investigated the functional impact of alternative splicing at exons 43 and 44, using whole-cell analysis of recombinant channels expressed in HEK 293 cells. While all combinations showed facilitation, splice variation produced subtle differences in the strength of ...

Recombinant P/Q-type α1A) Ca2+ channels exhibit novel forms of Ca2+-dependent facilitation and inactivation (Lee et al, Nature 399:155), which may support short-term synaptic plasticity at central synapses (Borst et al, J Physiol, 513:149; Cuttle et al, ibid, 512:723). Both facilitation and inactivation reportedly involve calmodulin (CaM) binding to a CBD domain, situated on the distal α1A. carboxyl tail. By contrast, we recently found that Ca2+-dependent inactivation of L-type (α1C) Ca2+ channels relies on CaM binding to an IQ-like domain in the proximal carboxyl tail (Peterson et al, Neuron, 22:549), and an analogous motif on α1A (IQA) exhibits robust CaM binding. Here, we report that IQA is a critical structural determinant of both facilitation and inactivation in P/Q channels. Facilitation of wildtype P/Q channels (α1A β2a α2δ) is apparent during prepulse protocols with Ca2+ as charge carrier (A, middle row), where test-pulse currents without a prepulse (gray) slowly increased with maintained Ca2+ entr...

This study complements a prior study of chronic delta-9-THC effects on memory during a delayed-nonmatching-to-sample task (Deadwyler et al 1995). Rats were exposed to a single high dose (3.75 mg/kg) of WIN 55,212-2 (WIN-2) before each DNMS session for a 35 day period. Tolerance to the memory debilitating effects of WIN-2 developed over 35 days, with eventual recovery of control performance despite initial impairment from the high dose. On day 36, withdrawal was precipitated with the CB1 receptor antagonist SR141617A (5.0 mg/kg, NIDA), producing frank behavioral withdrawal (Rubino et al. 1998), and depression of DNMS performance. These effects dissipated within 2-4 days and performance returned to normal. Simultaneous recording of ensembles of hippocampal neurons revealed that initial exposure to WIN-2 produced a >40% decrease in Sample and Delay phase ensemble coded firing (Heyser et al 1993), reflecting the selective suppression of functional cell types that preferentially fire during those phases of t...

Methamphetamine (METH) abusers have cognitive deficits that may contribute to their addiction. We aim to identify abnormalities in brain function that underlie such disturbances. Participants were paid volunteers (21–50 y). Abusers reported heavy METH use and no other major drug use; controls engaged in no substantial illicit substance abuse (light marijuana and alcohol allowed in both groups). METH users abstained for 5–11 days. Absolute regional and global cerebral glucose metabolism (rCMRglc, CMRglc) were assayed with PET and the [F-18]fluorodeoxyglucose method during performance of an attentional task. METH users (n=5) had 9% lower CMRglc than controls (n=4). The differences in cerebellar vermis, caudate nucleus (n.) and putamen were of similar magnitude (about 9–9.75%), while the orbitofrontal gyrus (OFC) showed a slightly greater decrement (10.5%). Analysis of normalized data (n=5)indicated elevated rCMRglc in inferior parietal lobule and cuneus of METH subjects. Considering the absolute metabolic ra...

Abundant filamentous tau inclusions in oligodendrocytes (OLGs) are hallmarks of neurodegenerative tauopathies, including sporadic corticobasal degeneration and hereditary frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). However, mechanisms of neurodegeneration in these tauopathies are unclear in part because of the lack of animal models for experimental analysis. We address this by generating transgenic (Tg) mice expressing human tau exclusively in OLGs using the 2′,3′-cyclic nucleotide 3′-phosphodiesterase promoter. Filamentous OLG tau inclusions developed in these Tg mice as a result of human tau expression in OLGs, especially those expressing the FTDP-17 human P301L mutant tau. Notably, structural disruption of myelin and axons preceded the emergence of thioflavin-S positive tau inclusions in OLGs, but impairments in axonal transport occurred even earlier, whereas motor deficits developed subsequently, especially in Tg mice with the highest tau expression levels. These data s...

Methylenedioxymethamphetamine (MDMA; “Ecstasy”) is a popular recreational drug and brain serotonin (5-HT) neurotoxin. Neuroimaging data indicate that some human MDMA users develop persistent deficits in brain 5-HT neuronal markers. Although the consequences of MDMA-induced 5-HT neurotoxicity are not fully understood, abstinent MDMA users have been found to have subtle cognitive deficits and altered sleep architecture. The present study sought to test the hypothesis that sleep disturbance plays a role in cognitive deficits in MDMA users. Nineteen abstinent MDMA users and 21 control subjects participated in a 5 d inpatient study in a clinical research unit. Baseline sleep quality was measured using the Pittsburgh Sleep Quality Inventory. Cognitive performance was tested three times daily using a computerized cognitive battery. On the third day of admission, subjects began a 40 h sleep deprivation period and continued cognitive testing using the same daily schedule. At baseline, MDMA users performed less accu...

Drug addiction is likely to affect all of our lives, with any luck not through our own actions but probably because of one or more of our family and friends. Now firmly entrenched as a brain disease ([Leshner, 1999][1]; [Wise, 2000][2]), drug addiction is among the most costly such diseases in

The localization of cannabinoid (CB) receptors to GABAergic interneurons in the hippocampus indicates that CBs may modulate GABAergic function and thereby mediate some of the disruptive effects of marijuana on spatial memory and sensory processing. To investigate the possible mechanisms through which CB receptors may modulate GABAergic neurotransmission in the hippocampus, whole-cell voltage-clamp recordings were performed on CA1 pyramidal neurons in rat brain slices. Stimulus-evoked GABAA receptor-mediated IPSCs were reduced in a concentration-dependent manner by the CB receptor agonist WIN 55,212–2 (EC50 of 138 nm). This effect was blocked by the CB1 receptor antagonist SR141716A (1 μm) but not by the opioid antagonist naloxone. In contrast, evoked GABAB-mediated IPSCs were insensitive to the CB agonist. WIN 55,212–2 also reduced the frequency of spontaneous, action potential-dependent IPSCs (sIPSCs), without altering action potential-independent miniature IPSCs (mIPSCs), measured while sodium channels w...