The association of clinical phenotypes to known AD/FTD genetic risk loci and their inter-relationship.

To elucidate how variants in genetic risk loci previously implicated in Alzheimer's Disease (AD) and/or frontotemporal dementia (FTD) contribute to expression of disease phenotypes, a phenome-wide association study was performed in two waves. In the first wave, we explored clinical traits associated with thirteen genetic variants previously reported to be linked to disease risk using both the 23andMe and UKB cohorts. We tested 30 additional AD variants in UKB cohort only in the second wave. APOE variants defining ε2/ε3/ε4 alleles and rs646776 were identified to be significantly associated with metabolic/cardiovascular and longevity traits. APOE variants were also significantly associated with neurological traits. ABI3 variant rs28394864 was significantly associated with cardiovascular (e.g. (hypertension, ischemic heart disease, coronary atherosclerosis, angina) and immune-related trait asthma. Both APOE variants and CLU variant were significantly associated with nearsightedness. HLA- DRB1 variant was associated with diseases with immune-related traits. Additionally, variants from 10+ AD genes (BZRAP1-AS1, ADAMTS4, ADAM10, APH1B, SCIMP, ABI3, SPPL2A, ZNF232, GRN, CD2AP, and CD33) were associated with hematological measurements such as white blood cell (leukocyte) count, monocyte count, neutrophill count, platelet count, and/or mean platelet (thrombocyte) volume (an autoimmune disease biomarker). Many of these genes are expressed specifically in microglia. The associations of ABI3 variant with cardiovascular and immune-related traits are one of the novel findings from this study. Taken together, it is evidenced that at least some AD and FTD variants are associated with multiple clinical phenotypes and not just dementia. These findings were discussed in the context of causal relationship versus pleiotropy via Mendelian randomization analysis.

On the horizon-the value and promise of the global pipeline of Alzheimer's disease therapeutics.

INTRODUCTION: The recent failure of several late-stage Alzheimer's disease (AD) clinical trials focused on amyloid beta (Aß) highlights the challenges of finding effective disease-modifying therapeutics. Despite major advances in our understanding of the genetic risk factors of disease and the development of clinical biomarkers, and that not all Aß-based approaches are equivalent, these failures may engender skepticism regarding the value of the AD pipeline. METHODS: To investigate these concerns, we compiled a database of current Phase 2 and 3 trials based on disease-modifying targets through a query of the National Institutes of Health's ClinicalTrials.gov. We then assessed the financial value of the pipeline. Financial modeling utilized risk-adjusted net present value (rNPV) measurements and included sensitivity analyses to help inform the drug development process. RESULTS: Results indicate that the preponderance of current Phase 3 trials were indeed targeting Aß, with only 15% addressing other targets. In contrast, the pipeline of Phase 2 trials was more diverse. The estimated rNPV of Phase 2 and 3 therapeutics was estimated to be $338 billion over 10 years. This figure increased to a theoretical cumulative value of $788 billion when incorporating the assumption that diagnostics will be developed to identify individuals at high risk for developing AD. Results from model sensitivity analyses showed that speed of market penetration and patient access contributed the most weight to financial value. In contrast, decreasing drug development costs had minimal impact on rNPV. DISCUSSION: These findings argue in favor of conducting thorough biomarker-driven Phase 2 proof of concept studies to avoid prematurely advancing assets into Phase 3. Insights from these analyses are also discussed in the context of the financial ecosystem needed to maintain a healthy AD pipeline.

Aiding the discovery of new treatments for dementia by uncovering unknown benefits of existing medications.

INTRODUCTION: There is a significant need for disease-modifying therapies to treat and prevent dementia, including Alzheimer's disease. Availability of real-world observational information and new analytic techniques to analyze large volumes of data can provide a path to aid drug discovery. METHODS: Using a self-controlled study design, we examined the association between 2181 medications and incidence of dementia across four US insurance claims databases. Medications associated with ≥50% reduction in risk of dementia in ≥2 databases were examined. RESULTS: A total of 117,015,066 individuals were included in the analysis. Seventeen medications met our threshold criteria for a potential protective effect on dementia and fell into five classes: catecholamine modulators, anticonvulsants, antibiotics/antivirals, anticoagulants, and a miscellaneous group. DISCUSSION: The biological pathways of the medications identified in this analysis may be targets for further research and may aid in discovering novel therapeutic approaches to treat dementia. These data show association not causality.

Comprehensive Real-World Assessment of Marketed Medications to Guide Parkinson's Drug Discovery.

BACKGROUND: Parkinson's disease is a disorder growing in prevalence, disability, and deaths. Healthcare databases provide a 'real-world' perspective for millions of individuals. We envisioned helping accelerate drug discovery by using these databases. OBJECTIVES: The objectives of this study were to assess the association of marketed medications with the risk of parkinsonism in four US claims databases and to evaluate the consistency of the association of ß-adrenoreceptor modulation with parkinsonism. METHODS: The study was conducted using a self-controlled cohort design in which subjects served as their own control. The time from treatment initiation until discontinuation or end of observation was the exposed period and a similar time preceding medication was the unexposed period. Medications were studied at ingredient and class level. The incidence rate ratio (IRR) and combined IRR were calculated. RESULTS: We assessed 2181 drugs and 117,015,066 people. Diphenhydramine, isradipine, methylphenidate, armodafinil, and modafinil were associated with reduced risk for parkinsonism in at least two databases. Armodafinil, modafinil, methylphenidate, and the ß-agonist albuterol were associated with a 56%, 54%, 39%, and 17% reduction in the risk of having parkinsonism, respectively. Isradipine results were heterogeneous and no significant association was found. Propranolol was associated with a 32% increased risk, the only ß-adrenoceptor antagonist (ß-blocker) associated with an increased risk. CONCLUSIONS: Armodafinil, modafinil, and methylphenidate were associated with a decreased risk of parkinsonism, as were ß-agonists. Of the ß-blockers, only propranolol was associated with increased risk. Healthcare database analyses that incorporate scientific rigor provide insight and direction for drug discovery efforts. These findings show association not causality; however, they offer considerable support to the association between ß-adrenergic receptor modulation and risk of Parkinson's disease.

Discovery of 3-substituted aminocyclopentanes as potent and orally bioavailable NR2B subtype-selective NMDA antagonists.

A series of 3-substituted aminocyclopentanes has been identified as highly potent and selective NR2B receptor antagonists. Incorporation of a 1,2,4-oxadiazole linker and substitution of the pendant phenyl ring led to the discovery of orally bioavailable analogues that showed efficient NR2B receptor occupancy in rats. Unlike nonselective NMDA antagonists, the NR2B-selective antagonist 22 showed no adverse affects on motor coordination in the rotarod assay at high dose. Compound 22 was efficacious following oral administration in a spinal nerve ligation model of neuropathic pain and in an acute model of Parkinson's disease in a dose dependent manner.

A study of long-term potentiation in transgenic mice over-expressing mutant forms of both amyloid precursor protein and presenilin-1.

Synaptic transmission and long-term potentiation (LTP) in the CA1 region of hippocampal slices have been studied during ageing of a double transgenic mouse strain relevant to early-onset familial Alzheimer's disease (AD). This strain, which over-expresses both the 695 amino acid isoform of human amyloid precursor protein (APP) with K670N and M671L mutations and presenilin 1 with the A246E mutation, has accelerated amyloidosis and plaque formation. There was a decrease in synaptic transmission in both wildtype and transgenic mice between 2 and 9 months of age. However, preparing slices from 14 month old animals in kynurenic acid (1 mM) counteracted this age-related deficit. Basal transmission and paired-pulse facilitation was similar between the two groups at all ages (2, 6, 9 and 14 months) tested. Similarly, at all ages LTP, induced either by theta burst stimulation or by multiple tetani, was normal. These data show that a prolonged, substantially elevated level of Abeta are not sufficient to cause deficits in the induction or expression of LTP in the CA1 hippocampal region.

Genome-wide microarray analysis of the differential neuroprotective effects of antioxidants in neuroblastoma cells overexpressing the familial Parkinson's disease alpha-synuclein A53T mutation.

In Parkinson's disease substantia nigra neurons degenerate likely due to oxidative damage interacting with genetic risk factors. Here, SH-SY5Y cells expressing wild-type or A53T alpha-synuclein had increased sensitivity to methyl-4-phenylpyridinium iodide (MPP(+)), which induces mitochondrial dysfunction, and 6-hydroxydopamine (6-OHDA), which causes oxidative stress. Edaravone protected only against MPP(+), and EGCG ((-)-epigallocatechin-3-O-gallate) protected only against 6-OHDA. Thus genomic responses to MPP(+) and 6-OHDA in the presence of these antioxidants were analyzed using microarrays. Pathway analysis indicated that MPP(+) activated p53 (P < 0.001) while 6-OHDA induced the Nrf2 antioxidative stress response (P < 0.0001). EGCG was more effective at blocking 6-OHDA-mediated genomic responses, while edaravone was more effective against MPP(+). We identified 32 genes that responded to both toxins except in the presence of an effective anti-oxidant; eight are transcription factors and potentially constitute a stress-response transcriptional network. These data provide insights into the mechanisms of neurotoxicity and identifies genes that might mediate antioxidant efficacy.

Selective activation of the M1 muscarinic acetylcholine receptor achieved by allosteric potentiation.

The forebrain cholinergic system promotes higher brain function in part by signaling through the M(1) muscarinic acetylcholine receptor (mAChR). During Alzheimer's disease (AD), these cholinergic neurons degenerate, therefore selectively activating M(1) receptors could improve cognitive function in these patients while avoiding unwanted peripheral responses associated with non-selective muscarinic agonists. We describe here benzyl quinolone carboxylic acid (BQCA), a highly selective allosteric potentiator of the M(1) mAChR. BQCA reduces the concentration of ACh required to activate M(1) up to 129-fold with an inflection point value of 845 nM. No potentiation, agonism, or antagonism activity on other mAChRs is observed up to 100 microM. Furthermore studies in M(1)(-/-) mice demonstrates that BQCA requires M(1) to promote inositol phosphate turnover in primary neurons and to increase c-fos and arc RNA expression and ERK phosphorylation in the brain. Radioligand-binding assays, molecular modeling, and site-directed mutagenesis experiments indicate that BQCA acts at an allosteric site involving residues Y179 and W400. BQCA reverses scopolamine-induced memory deficits in contextual fear conditioning, increases blood flow to the cerebral cortex, and increases wakefulness while reducing delta sleep. In contrast to M(1) allosteric agonists, which do not improve memory in scopolamine-challenged mice in contextual fear conditioning, BQCA induces beta-arrestin recruitment to M(1), suggesting a role for this signal transduction mechanism in the cholinergic modulation of memory. In summary, BQCA exploits an allosteric potentiation mechanism to provide selectivity for the M(1) receptor and represents a promising therapeutic strategy for cognitive disorders.

Oxysterol-binding protein-1 (OSBP1) modulates processing and trafficking of the amyloid precursor protein.

BACKGROUND: Evidence from biochemical, epidemiological and genetic findings indicates that cholesterol levels are linked to amyloid-beta (Abeta) production and Alzheimer's disease (AD). Oxysterols, which are cholesterol-derived ligands of the liver X receptors (LXRs) and oxysterol binding proteins, strongly regulate the processing of amyloid precursor protein (APP). Although LXRs have been studied extensively, little is known about the biology of oxysterol binding proteins. Oxysterol-binding protein 1 (OSBP1) is a member of a family of sterol-binding proteins with roles in lipid metabolism, regulation of secretory vesicle generation and signal transduction, and it is thought that these proteins may act as sterol sensors to control a variety of sterol-dependent cellular processes. RESULTS: We investigated whether OSBP1 was involved in regulating APP processing and found that overexpression of OSBP1 downregulated the amyloidogenic processing of APP, while OSBP1 knockdown had the opposite effect. In addition, we found that OSBP1 altered the trafficking of APP-Notch2 dimers by causing their accumulation in the Golgi, an effect that could be reversed by treating cells with OSBP1 ligand, 25-hydroxycholesterol. CONCLUSION: These results suggest that OSBP1 could play a role in linking cholesterol metabolism with intracellular APP trafficking and Abeta production, and more importantly indicate that OSBP1 could provide an alternative target for Abeta-directed therapeutic.

Beyond amyloid: the next generation of Alzheimer's disease therapeutics.

The precise pathological events that cause cognitive deficits in Alzheimer's disease remain to be determined. The most widely held view is that accumulation of amyloid beta peptide initiates the disease process; however, with more than eighteen amyloid-based therapeutic candidates currently in clinical trials, the targeting of amyloid alone may not be sufficient to improve functional deficits over the course of the disease. Alternative targets, such as the tau protein and apolipoprotein E, have thus been increasingly investigated, and in the future, therapeutic strategies will likely address events that are upstream of a more broadly construed pathological cascade that includes but is not limited to the generation and accumulation of amyloid beta. Consideration of such events provides the basis for an "indirect amyloid hypothesis," for which data are beginning to emerge. Although it is clinically defined by simple post-mortem criteria, Alzheimer's disease likely has a complex etiology, and effective treatments for this disease will become ever more urgent as the world's population ages.

Design, synthesis, and SAR of macrocyclic tertiary carbinamine BACE-1 inhibitors.

This Letter describes the design and synthesis of tertiary carbinamine macrocyclic inhibitors of the beta-secretase (BACE-1) enzyme. These macrocyclic inhibitors, some of which incorporate novel P2 substituents, display a 2- to 100-fold increase in potency relative to the previously described acyclic analogs while affording greater stability.

LRRTM3 promotes processing of amyloid-precursor protein by BACE1 and is a positional candidate gene for late-onset Alzheimer's disease.

Rare familial forms of Alzheimer's disease (AD) are thought to be caused by elevated proteolytic production of the Abeta42 peptide from the beta-amyloid-precursor protein (APP). Although the pathogenesis of the more common late-onset AD (LOAD) is not understood, BACE1, the protease that cleaves APP to generate the N terminus of Abeta42, is more active in patients with LOAD, suggesting that increased amyloid production processing might also contribute to the sporadic disease. Using high-throughput siRNA screening technology, we assessed 15,200 genes for their role in Abeta42 secretion and identified leucine-rich repeat transmembrane 3 (LRRTM3) as a neuronal gene that promotes APP processing by BACE1. siRNAs targeting LRRTM3 inhibit the secretion of Abeta40, Abeta42, and sAPPbeta, the N-terminal APP fragment produced by BACE1 cleavage, from cultured cells and primary neurons by up to 60%, whereas overexpression increases Abeta secretion. LRRTM3 is expressed nearly exclusively in the nervous system, including regions affected during AD, such as the dentate gyrus. Furthermore, LRRTM3 maps to a region of chromosome 10 linked to both LOAD and elevated plasma Abeta42, and is structurally similar to a family of neuronal receptors that includes the NOGO receptor, an inhibitor of neuronal regeneration and APP processing. Thus, LRRTM3 is a functional and positional candidate gene for AD, and, given its receptor-like structure and restricted expression, a potential therapeutic target.

L-655,708 enhances cognition in rats but is not proconvulsant at a dose selective for alpha5-containing GABAA receptors.

The in vitro and in vivo properties of L-655,708, a compound with higher affinity for GABA(A) receptors containing an alpha5 compared to an alpha1, alpha2 or alpha3 subunit have been examined further. This compound has weak partial inverse agonist efficacy at each of the four subtypes but, and consistent with the binding data, has higher functional affinity for the alpha5 subtype. In a mouse hippocampal slice model, L-655,708 was able to enhance the long-term potentiation produced by a theta burst stimulation, consistent with a potential role for the alpha5 subtype in processes involving synaptic plasticity, such as learning and memory. When administered in a formulation specifically designed to achieve relatively constant plasma drug concentrations, and therefore maintain selective occupancy of alpha5- compared to alpha1-, alpha2- and alpha3-containing receptors (75+/-4% versus 22+/-10%, respectively), L-655,708 did not alter the dose of pentylenetetrazole required to induce seizures, indicating that the inverse agonist effects of L-655,708 at the alpha5 subtype are not associated with a proconvulsant liability. In the Morris water maze, L-655,708 enhanced performance not only during acquisition but also in a probe trial, demonstrating that this compound has cognition enhancing effects. These data further support the potential of alpha5-containing GABA(A) receptors as a target for novel cognition enhancing drugs.

Functional characterisation of the S512Y mutant vanilloid human TRPV1 receptor.

1 Mammalian transient receptor potential (TRP) channels include the nonselective cation channel TRPV1, which is activated by a range of stimuli including low pH, vanilloids and heat. Previously, selective mutagenesis experiments identified an intracellular residue (S512Y) critical to discriminating between pH and vanilloid (capsaicin) gating of the rat TRPV1 receptor. 2 In this study, switching the equivalent residue in the human TRPV1 (which has some significant differences with the rat TRPV1) also rendered this channel relatively insensitive to activation by capsaicin and proved critical in determining the receptor's sensitivity to the putative endovanilloid N-arachidonoyl-dopamine (NADA), suggesting a similar mode of activation for these two agonists. 3 Potency of pH gating was reduced; however, voltage-dependent outward rectification properties of the pH-dependent current and gating by heat and pH sensitisation of the S512Y heat response remained unaffected. 4 Surprisingly, residual capsaicin gating was detected and could be sensitised by pH even in the presence of a competitive antagonist. Taken together, these findings indicate that effective functional interaction of capsaicin with the S512Y channel still occurred, although the vanilloid-dependent gating per se was severely compromised. 5 This observation provides additional evidence for capsaicin interacting at multiple sites, distinct from the S512 residue located close to the intracellular face of the pore.

Increased nuclear factor-erythroid 2 p45-related factor 2 activity protects SH-SY5Y cells against oxidative damage.

The ability of cells to control the balance between the generation and quenching of reactive oxygen species is important in combating potentially damaging effects of oxidative stress. One mechanism that cells use to maintain redox homeostasis is the antioxidant response pathway. Antioxidant response elements (AREs) are cis-acting elements located in regulatory regions of antioxidant and phase II detoxification genes. Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) is a member of the Cap 'n' Collar family of transcription factors that binds to the ARE and regulates the transcription of specific ARE-containing genes such as NAD(P)H:quinone oxidoreductase 1, glutamylcysteine synthetase and heme oxygenase. Activation of Nrf2 results in release from its negative repressor, Kelch-like ECH-associated protein 1 (Keap1), and allows Nrf2 to translocate into the nucleus to induce gene expression. In this study, we demonstrate that increasing Nrf2 activity by various methods, including chemical induction, Nrf2 overexpression or Keap1 siRNA knockdown, protects cells against specific types of oxidative damage. Cells were protected against 6-hydroxydopamine- and 3-morpholinosydnonimine-mediated toxicity but not against 1-methyl-1-4-phenylpyridinium toxicity. As oxidative stress is a hallmark of several neurodegenerative disorders, including Parkinson's disease, pharmacological agents that selectively target the Keap1-Nrf2 pathway may provide a novel neuroprotective strategy for the treatment of these diseases.

Group III metabotropic glutamate-receptor-mediated modulation of excitatory transmission in rodent substantia nigra pars compacta dopamine neurons.

Glutamate plays an important role in the regulation of dopamine neuron activity. In particular, the glutamatergic input from the subthalamic nucleus is thought to provide control over dopamine neuron firing patterns. The degeneration of dopamine neurons in the substantia nigra pars compacta (SNc) observed in Parkinson's disease (PD) is believed to be due to a complex interplay of factors, including oxidative stress and mitochondrial dysfunction. Although glutamate is not the primary cause of cell death in PD, there is evidence suggesting excessive glutamate release onto dopamine neurons may play a role in continued degeneration. Although many studies have focused on the role of glutamate in the SNc, little work has been directed at exploring the modulatory control of glutamate release in this region. Previous studies have found a high-potency inhibitory effect of nonselective group III mGluR agonist on glutamatergic transmission in the SNc. Using whole-cell patch-clamp methods and novel pharmacological tools, we have determined that mGluR4 mediates the group III mGluR modulation of excitatory transmission in the rat SNc. The group III mGluR-selective agonist l-(+)-2-amino-4-phosphonobutyric acid inhibits excitatory transmission in the SNc at low micromolar concentrations with a maximal inhibition occurring at 3 muM. This effect was potentiated by the mGluR4-selective allosteric modulator N-phenyl-7-(hydroxymino)cyclopropa[b]chromen-1a-carboxamide and was not mimicked by the mGluR8-selective agonist (S)-3,4-dicarboxyphenylglycine. Interestingly, in an attempt to employ knockout mice to confirm the role of mGluR4, we discovered an apparent species difference suggesting that in mice, both mGluR4 and mGluR8 modulate excitatory transmission in the SNc.

Clozapine potentiation of N-methyl-D-aspartate receptor currents in the nucleus accumbens: role of NR2B and protein kinase A/Src kinases.

Clozapine is an atypical antipsychotic that has a unique clinical profile that distinguishes it from other typical and atypical antipsychotics. At present, the underlying mechanisms of action of clozapine are unclear. Recent studies in the field of schizophrenia suggest that compounds that potentiate N-methyl-d-aspartate (NMDA) receptor function in the appropriate brain regions might be an effective antipsychotic agent. One relevant region in which NMDA receptors play a key role in mediating neurotransmission is the nucleus accumbens. Therefore, we investigated the regulation of NMDA receptor currents and excitatory postsynaptic currents (EPSCs) by clozapine in nucleus accumbens neurons. Whole-cell patch-clamp recordings were performed in rat brain slices. We demonstrate that bath application of clozapine but not haloperidol or the selective 5-hydroxytryptamine 2A antagonist MDL100907 [(R)-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluoro-phenyl)ethyl]-4-piperidine methanol] induces a robust potentiation of NMDA-evoked currents and of glutamatergic EPSCs and that this potentiation is dependent on dopamine release and postsynaptic activation of D1 receptors. Furthermore, the effect of clozapine is selective for NR2B subtype-containing NMDA receptors and is blocked by the selective Src family kinase inhibitor PP2 [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine] and the protein kinase A-selective inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide but not by the protein kinase C-selective inhibitor bisindolylmaleimide I. This effect of clozapine in the nucleus accumbens might underlie the unique clinical profile of this atypical antipsychotic and provides a basis for novel treatment approaches.

Synthesis and biological evaluation of 3-heterocyclyl-7,8,9,10-tetrahydro-(7,10-ethano)-1,2,4-triazolo[3,4-a]phthalazines and analogues as subtype-selective inverse agonists for the GABA(A)alpha5 benzodiazepine binding site.

The identification of a novel series of 7,8,9,10-tetrahydro-(7,10-ethano)-1,2,4-triazolo[3,4-a]phthalazines as GABA(A)alpha5 inverse agonists, which have both binding and functional (efficacy) selectivity for the benzodiazepine binding site of alpha5- over alpha1-, alpha2-, and alpha3-containing GABA(A) receptor subtypes, is described. Binding selectivity was determined to a large part by the degree of planarity of the fused ring system whereas functional selectivity was dependent on the nature of the heterocycle at the 3-position of the triazolopyridazine ring. 3-Furan and 5-methylisoxazole were shown to be optimal for GABA(A)alpha5 functional selectvity. 3-(5-Methylisoxazol-3-yl)-6-(2-pyridyl)methyloxy-1,2,4-triazolo[3,4-a]phthalazine (43) was identified as a full inverse agonist at the GABA(A)alpha5 subtype with functional selectivity over the other GABA(A) receptor subtypes and good oral bioavailability.

Triazolam suppresses the induction of hippocampal long-term potentiation.

Benzodiazepines are sedative hypnotics that produce marked anterograde amnesia in humans. These pharmacological properties are thought to result from the potentiation of GABA-A receptor function and subsequent attenuation of long-term potentiation (LTP), however many reports have suggested this is not the case for triazolam. Using electrophysiological recordings in a cell line expressing recombinant GABA-A receptors, we confirm that triazolam is an efficacious positive allosteric modulator of GABA-A receptors. Triazolam also slowed the decay of spontaneous inhibitory synaptic currents, reduced the amplitude of fEPSPs elicited during a theta burst and reduced the magnitude of LTP in hippocampal CA1 neurones in vitro. These data show that triazolam modifies LTP induction consistent with an enhancement of GABA-A receptor function via activation of the allosteric benzodiazepine-site.

Discrete expression of TRPV2 within the hypothalamo-neurohypophysial system: Implications for regulatory activity within the hypothalamic-pituitary-adrenal axis.

Transient receptor potential channel proteins (TRPs) constitute a steadily growing family of ion channels with a range of purported functions. It has been demonstrated that TRPV2 is activated by moderate thermal stimuli and, in the rat, is expressed in medium to large diameter dorsal root ganglion neurons. In this study, antisera specific for the human TRPV2 homologue were raised and characterized for immunohistochemical use. Subsequently, thorough investigation was made of the localization of this cation channel in the macaque primate brain. TRPV2-immunoreactive material was highly restrictively localized to hypothalamic paraventricular, suprachiasmatic, and supraoptic nuclei. Confocal double- and triple-labeling studies demonstrated that TRPV2 immunoreactivity is preferentially localized to oxytocinergic and vasopressinergic neurons. Few, if any, cells in these regions expressed TRPV2 immunoreactivity in the absence of oxytocin immunoreactivity or vasopressin immunoreactivity. Expression in the paraventricular and supraoptic nuclei suggests that TRPV2 is likely to play a fundamental role in mediating cation transport in neurohypophysial neurons. TRPV2 has been shown to be translocated upon cell activation and neurons expressing TRPV2 immunoreactivity in vivo are among those known to engage in sporadic, intense activity. Taken together, these data suggest that this channel may play a vital role in mediating physiological activities associated with oxytocin and vasopressin release such as parturition, lactation, and diuresis. These data may also implicate the involvement of TRPV2 in disorders of the hypothalamic-pituitary-adrenal axis, including anxiety, depression, hypertension, and preterm labor.