Boron-Nitrogen-Containing Benzene Valence Isomers.

Benzene is one of the most ubiquitous structural motifs in chemistry. The valence isomers of benzene have also attracted synthetic chemists' attention due to their unique structures, bonding, and reactivity. We have been investigating boron-nitrogen-containing benzene valence isomers via photoisomerization of 1,2-azaborines. In this contribution, we summarize recent developments of these highly strained BN-heterocyclic compounds including their synthesis, characterization, proposed mechanism of formation, and their potential applications.

A BN-Benzvalene.

The synthesis and crystallographic characterization of BN-benzvalene, the first second-row heteroatom-containing benzvalene, is described. BN-benzvalenes are produced via photoexcitation of C5-aryl-substituted 1,2-azaborines under flow conditions. Mechanistic studies support a boron-specific, two-step photoisomerization pathway involving a BN-Dewar benzene intermediate, which is distinct from the photoisomerization pathway proposed in benzene and phospha- and silabenzenes for the formation of their respective benzvalene analogues.

Glypican-2 defines age-dependent axonal response to chondroitin sulfate.

Axons of terminally differentiated neurons in the mammalian central nervous system (CNS) are unable to regenerate after dissection. One of the mechanisms underlying this is the inhibition of axonal regeneration by chondroitin sulfate (CS) and its neuronal receptor, PTPσ. Our previous results demonstrated that the CS-PTPσ axis disrupted autophagy flux by dephosphorylating cortactin, which led to the formation of dystrophic endballs and to the inhibition of axonal regeneration. In contrast, juvenile neurons vigorously extend axons toward their targets during development and maintain regenerative activity for axons even after injury. Although several intrinsic and extrinsic mechanisms have been reported to mediate the differences, the detailed mechanisms are still elusive. Here, we report that Glypican-2, a member of heparan sulfate proteoglycans (HSPG), which are able to antagonize CS-PTPσ by competing with the receptor, is specifically expressed in the axonal tips of embryonic neurons. Glypican-2 overexpression in adult neurons rescues the dystrophic endball back to a healthy growth cone on the CSPG gradient. Consistently, Glypican-2 restored cortactin phosphorylation in the axonal tips of adult neurons on CSPG. Taken together, our results clearly demonstrated Glypican-2's pivotal role in defining the axonal response to CS and provided a new therapeutic target for axonal injury.

The aromatic Claisen rearrangement of a 1,2-azaborine.

The first aromatic Claisen rearrangement of a 1,2-azaborine is described along with a quantitative kinetic comparison of the reaction of the azaborine with its direct all-carbon analogue. The azaborine A rearranged in a clean, regioselective fashion and reacted faster than the all-carbon substrate B at all temperatures from 140-180 °C. Activation free energies were extracted from observed first-order rate constants (A: ΔG‡298K = 32.7 kcal mol-1; B: ΔG‡298K = 34.8 kcal mol-1) corresponding to a twenty fold faster rate for A at observed reaction temperatures. DFT calculations show that the rearrangement proceeds via a concerted six-membered transition state and that the electronic structure of the BN and CC rings is mostly responsible for the observed regioselectivity and relative reactivity.

Close association of polarization and LC3, a marker of autophagy, in axon determination in mouse hippocampal neurons.

The autophagy-lysosome pathway is a cellular clearance system for intracellular organelles, macromolecules and microorganisms. It is indispensable for cells not only to maintain their homeostasis but also to achieve more active cellular processes such as differentiation. Therefore, impairment or disruption of the autophagy-lysosome pathway leads to a wide spectrum of human diseases, ranging from several types of neurodegenerative diseases to malignancies. In elongating axons, autophagy preferentially occurs at growth cones, and disruption of autophagy is closely associated with incapacity for axonal regeneration after injury in the central nervous system. However, the roles of autophagy in developing neurons remain elusive. In particular, whether autophagy is involved in axon-dendrite determination is largely unclear. Using primary cultured mouse embryonic hippocampal neurons, we here showed the polarized distribution of autophagosomes among minor processes of neurons at stage 2. Time-lapse observation of neurons from GFP-LC3 transgenic mice demonstrated that an "LC3 surge"-i.e., a rapid accumulation of autophagic marker LC3 that continues for several hours in one minor process-proceeded the differentiation of neurons into axons. In addition, pharmacological activation and inhibition of autophagy by trehalose and bafilomycin, respectively, accelerated and delayed axonal determination. Taken together, our findings revealed the close association between LC3, a marker of autophagy, and axon determination in developing neurons.

Basigin deficiency prevents anaplerosis and ameliorates insulin resistance and hepatosteatosis.

Monocarboxylates, such as lactate and pyruvate, are precursors for biosynthetic pathways, including those for glucose, lipids, and amino acids via the tricarboxylic acid (TCA) cycle and adjacent metabolic networks. The transportation of monocarboxylates across the cellular membrane is performed primarily by monocarboxylate transporters (MCTs), the membrane localization and stabilization of which are facilitated by the transmembrane protein basigin (BSG). Here, we demonstrate that the MCT/BSG axis sits at a crucial intersection of cellular metabolism. Abolishment of MCT1 in the plasma membrane was achieved by Bsg depletion, which led to gluconeogenesis impairment via preventing the influx of lactate and pyruvate into the cell, consequently suppressing the TCA cycle. This net anaplerosis suppression was compensated in part by the increased utilization of glycogenic amino acids (e.g., alanine and glutamine) into the TCA cycle and by activated ketogenesis through fatty acid ß-oxidation. Complementary to these observations, hyperglycemia and hepatic steatosis induced by a high-fat diet were ameliorated in Bsg-deficient mice. Furthermore, Bsg deficiency significantly improved insulin resistance induced by a high-fat diet. Taken together, the plasma membrane-selective modulation of lactate and pyruvate transport through BSG inhibition could potentiate metabolic flexibility to treat metabolic diseases.

Primary Sulfonamide Functionalization via Sulfonyl Pyrroles: Seeing the N-Ts Bond in a Different Light.

Despite common occurrence in molecules of value, methods for transforming sulfonamides are distinctly lacking. Here we introduce easy-to-access sulfonyl pyrroles as synthetic linchpins for sulfonamide functionalization. The versatility of the sulfonyl pyrrole unit is shown by generating a variety of products through chemical, electrochemical and photochemical pathways. Preliminary results on the direct functionalization of primary sulfonamides are also provided, which may lead to new modes of activation.

Dermatan sulphate is an activating ligand of anaplastic lymphoma kinase.

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that harbours a tyrosine kinase domain in its intracellular region and is expressed in both central and peripheral nervous systems. RTKs are activated upon ligand binding and receptor clustering; however, ALK remains an orphan receptor despite its pathological significance, especially in malignancy. Recent biochemical work showed that heparan sulphate (HS), an unbranched sulphated glycan, acts as a ligand for and activates ALK. Here, we show that dermatan sulphate (DS, chondroitin sulphate B) directly interacts with the extracellular N-terminal region of ALK as well as HS. The tetrasaccharide of DS was required and was sufficient for inducing autophosphorylation of ALK at tyrosine 1604, a marker for activated ALK. Interestingly, longer oligosaccharides caused enhanced activation of ALK, as was the case for HS. Our results provide a novel example of glycans as signalling molecules and shed light on the pathophysiological roles of ALK.

Axonal Regeneration by Glycosaminoglycan.

Like other biomolecules including nucleic acid and protein, glycan plays pivotal roles in various cellular processes. For instance, it modulates protein folding and stability, organizes extracellular matrix and tissue elasticity, and regulates membrane trafficking. In addition, cell-surface glycans are often utilized as entry receptors for viruses, including SARS-CoV-2. Nevertheless, its roles as ligands to specific surface receptors have not been well understood with a few exceptions such as selectins and siglecs. Recent reports have demonstrated that chondroitin sulfate and heparan sulfate, both of which are glycosaminoglycans, work as physiological ligands on their shared receptor, protein tyrosine phosphatase sigma (PTPσ). These two glycans differentially determine the fates of neuronal axons after injury in our central nervous system. That is, heparan sulfate promotes axonal regeneration while chondroitin sulfate inhibits it, inducing dystrophic endbulbs at the axon tips. In our recent study, we demonstrated that the chondroitin sulfate (CS)-PTPσ axis disrupted autophagy flux at the axon tips by dephosphorylating cortactin. In this minireview, we introduce how glycans work as physiological ligands and regulate their intracellular signaling, especially focusing on chondroitin sulfate.

Type IIa RPTPs and Glycans: Roles in Axon Regeneration and Synaptogenesis.

Type IIa receptor tyrosine phosphatases (RPTPs) play pivotal roles in neuronal network formation. It is emerging that the interactions of RPTPs with glycans, i.e., chondroitin sulfate (CS) and heparan sulfate (HS), are critical for their functions. We highlight here the significance of these interactions in axon regeneration and synaptogenesis. For example, PTPσ, a member of type IIa RPTPs, on axon terminals is monomerized and activated by the extracellular CS deposited in neural injuries, dephosphorylates cortactin, disrupts autophagy flux, and consequently inhibits axon regeneration. In contrast, HS induces PTPσ oligomerization, suppresses PTPσ phosphatase activity, and promotes axon regeneration. PTPσ also serves as an organizer of excitatory synapses. PTPσ and neurexin bind one another on presynapses and further bind to postsynaptic leucine-rich repeat transmembrane protein 4 (LRRTM4). Neurexin is now known as a heparan sulfate proteoglycan (HSPG), and its HS is essential for the binding between these three molecules. Another HSPG, glypican 4, binds to presynaptic PTPσ and postsynaptic LRRTM4 in an HS-dependent manner. Type IIa RPTPs are also involved in the formation of excitatory and inhibitory synapses by heterophilic binding to a variety of postsynaptic partners. We also discuss the important issue of possible mechanisms coordinating axon extension and synapse formation.

Enoxaparin promotes functional recovery after spinal cord injury by antagonizing PTPRσ.

The receptor-type protein tyrosine phosphatase sigma (PTPRσ) regulates axonal regeneration/sprouting as a molecular switch in response to glycan ligands. Cell surface heparan sulfate oligomerizes PTPRσ and inactivates its enzymatic activity, which in turn promotes axonal growth. In contrast, matrix-associated chondroitin sulfate monomerizes PTPRσ and activates it. This leads to dephosphorylation of its specific substrates, such as cortactin, resulting in a failure of axonal regeneration after injury. However, this molecular switch model has never been challenged in a clinical situation. In this study, we demonstrated that enoxaparin, a globally approved anticoagulant consisting of heparin oligosaccharides with an average molecular weight of 45 kDa, induced clustering and inactivated PTPRσ in vitro. Enoxaparin induced PTPRσ clustering, and counteracted PTPRσ-mediated dephosphorylation of cortactin, which was shown to be important for inhibition of axonal regeneration. Systemic administration of enoxaparin promoted anatomical recovery after both optic nerve and spinal cord injuries in rats at clinically tolerated doses. Moreover, enoxaparin promoted recovery of motor function without obvious hemorrhage. Collectively, our data provide a new strategy for the treatment of traumatic axonal injury.

Intracellular interplay between cholecystokinin and leptin signalling for satiety control in rats.

Cholecystokinin (CCK) and leptin are satiety-controlling peptides, yet their interactive roles remain unclear. Here, we addressed this issue using in vitro and in vivo models. In rat C6 glioma cells, leptin pre-treatment enhanced Ca2+ mobilization by a CCK agonist (CCK-8s). This leptin action was reduced by Janus kinase inhibitor (AG490) or PI3-kinase inhibitor (LY294002). Meanwhile, leptin stimulation alone failed to mobilize Ca2+ even in cells overexpressing leptin receptors (C6-ObRb). Leptin increased nuclear immunoreactivity against phosphorylated STAT3 (pSTAT3) whereas CCK-8s reduced leptin-induced nuclear pSTAT3 accumulation in these cells. In the rat ventromedial hypothalamus (VMH), leptin-induced action potential firing was enhanced, whereas nuclear pSTAT3 was reduced by co-stimulation with CCK-8s. To further analyse in vivo signalling interplay, a CCK-1 antagonist (lorglumide) was intraperitoneally injected in rats following 1-h restricted feeding. Food access was increased 3-h after lorglumide injection. At this timepoint, nuclear pSTAT3 was increased whereas c-Fos was decreased in the VMH. Taken together, these results suggest that leptin and CCK receptors may both contribute to short-term satiety, and leptin could positively modulate CCK signalling. Notably, nuclear pSTAT3 levels in this experimental paradigm were negatively correlated with satiety levels, contrary to the generally described transcriptional regulation for long-term satiety via leptin receptors.

Glycan sulfation patterns define autophagy flux at axon tip via PTPRσ-cortactin axis.

Chondroitin sulfate (CS) and heparan sulfate (HS) are glycosaminoglycans that both bind the receptor-type protein tyrosine phosphatase PTPRσ, affecting axonal regeneration. CS inhibits axonal growth, while HS promotes it. Here, we have prepared a library of HS octasaccharides and, together with synthetic CS oligomers, we found that PTPRσ preferentially interacts with CS-E-a rare sulfation pattern in natural CS-and most HS oligomers bearing sulfate and sulfamate groups. Consequently, short and long stretches of natural CS and HS, respectively, bind to PTPRσ. CS activates PTPRσ, which dephosphorylates cortactin-herein identified as a new PTPRσ substrate-and disrupts autophagy flux at the autophagosome-lysosome fusion step. Such disruption is required and sufficient for dystrophic endball formation and inhibition of axonal regeneration. Therefore, sulfation patterns determine the length of the glycosaminoglycan segment that bind to PTPRσ and define the fate of axonal regeneration through a mechanism involving PTPRσ, cortactin and autophagy.

Effect of the presence of trophectoderm vesicles on blastocyst in relation to in vitro hatching, clinical pregnancy, and miscarriage rates.

Trophectoderm vesicles (TVs) are observed in some blastocysts that penetrate cells from the zona pellucida to the outer margin. Therefore, we compared this incidence in relation to hatching, pregnancy, and miscarriage rates between conventional in vitro fertilization (c-IVF) and intracytoplasmic sperm injection (ICSI). Vitrified/warmed blastocysts (n = 112) were derived from surplus embryos. The blastocysts were then observed using time-lapse cinematography to resolve the relationship between hatching and implantation. Another study was conducted that comprised 681 embryo transfer cycles in 533 patients who received a single vitrified/warmed blastocyst from our clinic. The incidence of TV was significantly higher in embryos inseminated by ICSI compared with c-IVF [ICSI: 51/56 (91 %); c-IVF: 25/56 (45 %); P < 0.01]. The successful hatching rate was significantly lower in ICSI than in c-IVF [ICSI: 11/56 (20 %); c-IVF: 29/56 (52 %); P < 0.01]. In addition, the hatching rate was significantly lower when TVs were present (14/76; 18 %) than in non-TV embryos (26/36; 72 %) (P < 0.01). In regard to the clinical study results, no significant differences were found between the groups in the pregnancy rate (TV present group: 107/183, 58.5 %; TV absent group: 273/498, 54.8 %) and miscarriage rate (TV present group: 21/107, 19.6 %; TV absent group: 53/273, 19.4 %). In vivo, we hypothesized that hatching and hatched would occur naturally by assisting protease action in the uterus; therefore, these results suggest that the presence of TV has no effect on pregnancy rates in the clinical setting.

Serotonin-2C receptor involved serotonin-induced Ca²âº mobilisations in neuronal progenitors and neurons in rat suprachiasmatic nucleus.

The hypothalamic suprachiasmatic nucleus (SCN), the central circadian pacemaker in mammals, undergoes serotonergic regulation, but the underlying mechanisms remain obscure. Here, we generated a subclone of an SCN progenitor cell line expressing Ca(2+) sensors (SCN2.2YC) and compared its 5-HT receptor signalling with that of rat SCN neurons in brain slices. SCN2.2YC cells expressed 5-HT1A/2A/2B/2C, but not 5A/7, while all six subtypes were expressed in SCN tissues. High K(+) or 5-HT increased cytosolic Ca(2+) in SCN2.2YC cells. The 5-HT responses were inhibited by ritanserin and SB-221284, but resistant to WAY-100635 and RS-127445, suggesting predominant involvement of 5-HT2C for Ca(2+) mobilisations. Consistently, Ca(2+) imaging and voltage-clamp electrophysiology using rat SCN slices demonstrated post-synaptic 5-HT2C expression. Because 5-HT2C expression was postnatally increased in the SCN and 5-HT-induced Ca(2+) mobilisations were amplified in differentiated SCN2.2YC cells and developed SCN neurons, we suggest that this signalling development occurs in accordance with central clock maturations.

Acute enhancement of non-rapid eye movement sleep in rats after drinking water contaminated with cadmium chloride.

Cadmium (Cd) is a heavy metal widely used or effused by industries. Serious environmental Cd pollution has been reported over the past two centuries, whereas the mechanisms underlying Cd-mediated diseases are not fully understood. Interestingly, an increase in reactive oxygen species (ROS) after Cd exposure has been shown. Our group has demonstrated that sleep is triggered via accumulation of ROS during neuronal activities, and we thus hypothesize the involvement of Cd poisoning in sleep-wake irregularities. In the present study, we analyzed the effects of Cd intake (1-100 ppm CdCl2 in drinking water) on rats by monitoring sleep encephalograms and locomotor activities. The results demonstrated that 100 ppm CdCl2 administration for 28 h was sufficient to increase non-rapid-eye-movement (non-REM) sleep and reduce locomotor activities during the night (the rat active phase). In contrast, free-running locomotor rhythms under constant dim red light and their re-entrainment to 12:12-h light/dark cycles were intact under chronic (1 month) 100 ppm CdCl2 administrations, suggesting a limited influence on circadian clock movements at this dosage. The relative amount of oxidized glutathione increased in the brain after the 28-h 100 ppm CdCl2 administrations similar to the levels in cultured astrocytes receiving H2O2 or CdCl2 in culture medium. Therefore, we propose Cd-induced sleep as a consequence of oxidative stress. As oxidized glutathione is an endogenous sleep substance, we suggest that Cd rapidly induces sleepiness and influences activity performance by occupying intrinsic sleep-inducing mechanisms. In conclusion, we propose increased non-REM sleep during the active phase as an index of acute Cd exposure.

Infant satiety depends on transient expression of cholecystokinin-1 receptors on ependymal cells lining the third ventricle in mice.

Cholecystokinin (CCK) is a hypothetical controller for suckling and infancy body weight, although the underlying mechanisms remain unclear. Therefore, the present study analysed the mechanisms using mice lacking the CCK-1 receptor (CCK1R-/-). Although CCK1R-/- mice displayed normal weights at birth and adulthood, CCK1R-/- pups had enlarged adipocytes and were overweight from the first to second week after birth, regardless of maternal genotype. The lacZ reporter gene assay and/or calcium imaging analysis demonstrated that CCK-1 receptors were abundant in satiety-controlling regions such as the hypothalamus, brainstem, nodose ganglion and pylorus in adults, whereas these signals were few to lacking at pre-weanling stages. At postnatal day (PD) 6, the increase in cFos expression in the medullary nucleus tractus solitarius was similarly triggered by gastrointestinal milk- or saline filling in both genotypes, further indicating immature CCK-1 receptor function in an ascending satiety-controlling system during infancy. Conversely, third ventricle ependymal tanycyte-like cells expressed CCK-1 receptors with expression peaking at PD6. At PD6, wild-type but not CCK1R-/- mice had increased cFos immunoreactivity in ependymal cells following gastrointestinal milk filling whereas the response became negligible at PD12. In addition, ependymal cFos was not increased by saline filling, indicating that these responses are dependent on CCK-1 receptors, developmental stage and nutrients. Furthermore, body weights of wild-type pups were transiently increased by blocking ependymal CCK receptor function with microinjection of a CCK-1 antagonist, but not a CCK-2 antagonist. Hence, we demonstrate de novo functions of ependymal CCK-1 receptors and reveal a new aspect of infant satiety-controlling mechanisms.

Functional compensation between cholecystokinin-1 and -2 receptors in murine paraventricular nucleus neurons.

Cholecystokinin (CCK) and its receptor subtypes CCK-1 and -2 have diverse homeostatic functions. CCK-1 and -2 receptors share a common phosphatidylinositol signaling pathway, yet little is known regarding their possible functional coupling. We focused on CCK-mediated Ca(2+) signaling in parvocellular paraventricular nucleus (PVN) cells, which control satiety and other autonomic functions. Analysis of mouse hypothalamic slices demonstrated that the general CCK receptor agonist CCK-8s (10 nM) triggered Ca(2+) transients most significantly in the posterior subregion of the PVN (PaPo). This 10 nM CCK-8s-induced response was absent in CCK-1 receptor knock-out (CCK1R(-/-)) slices, showing that the response is mediated by CCK-1 receptors. CCK-8s concentrations higher than 30 nM triggered a Ca(2+) rise similarly in wild-type and CCK1R(-/-) slices. The large CCK-8s (100 nM)-induced Ca(2+) responses in CCK1R(-/-) slices were blocked by a CCK-2 receptor antagonist (CI-988), whereas those in wild-type slices required a mixture of CI-988 and lorglumide (a CCK-1 receptor antagonist) for complete antagonism. Therefore, CCK-1 and -2 receptors may function synergistically in single PaPo neurons and deletion of CCK-1 receptors may facilitate CCK-2 receptor signaling. This hypothesis was supported by results of real-time RT-PCR, immunofluorescence double labeling and Western blotting assays, which indicated CCK-2 receptor overexpression in PaPo neurons of CCK1R(-/-) mice. Furthermore, behavioral studies showed that intraperitoneal injections of lorglumide up-regulated food accesses in wild-type but not in CCK1R(-/-) mice, whereas CI-988 injections up-regulated food accesses in CCK1R(-/-) but not in wild-type mice. Compensatory CCK signaling via CCK-2 receptors in CCK1R(-/-) mice shed light on currently controversial satiety-controlling mechanisms.

First and second generation H1 histamine receptor antagonists produce different sleep-inducing profiles in rats.

First generation H1 histamine receptor antagonists, such as d-chlorpheniramine (d-CPA) and diphenhydramine, produce drowsiness in humans. They are currently used as over-the-counter sleep aids. However, the mechanisms underlying drowsiness induced by these H1 histamine receptor antagonists remain obscure because they produce heterogeneous receptor-independent actions. Ketotifen is a second generation H1 histamine receptor antagonist which is more permeable to the brain than newer H1 histamine receptor antagonists. Therefore, to access sleep-inducing profiles by H1 histamine receptor blocking actions, the present study compared the dose-dependent effects of diphenhydramine and ketotifen (1-40 mg/kg, intraperitoneal injection at dark onset time) on daily sleep-wake patterns in rats. Ketotifen dose-dependently decreased rapid-eye-movement (REM) sleep and increased non-REM sleep by amplifying slow-wave electroencephalogram powers. Diphenhydramine at 4 mg/kg transiently increased non-REM sleep and reduced REM sleep similar to the effects of ketotifen. The larger injections of diphenhydramine (10-40 mg/kg), however, reduced non-REM sleep, abolished slow-wave enhancements and facilitated wakefulness. The bi-directional action of diphenhydramine on sleep is similar to our former results using d-CPA. Taken together, the arousal effects caused by over-dose administrations of the first generation H1 histamine receptor antagonists may be mediated by H1 histamine receptor-independent actions. To further examine the tolerance of ketotifen-induced sleep, 3 mg/kg ketotifen was injected daily for 5 days 3 h before light onset time. These experiments consistently enhanced non-REM-sleep at the end of the active phase of rats, suggesting that ketotifen may function as a desirable sleep aid although the coincidental REM sleep reduction requires attention.

Induction of prolonged, continuous slow-wave sleep by blocking cerebral H1 histamine receptors in rats.

BACKGROUND AND PURPOSE: Classic H(1) histamine receptor (H(1)R) antagonists are non-selective for H(1)R and known to produce drowsiness. Modern antihistamines are more selective for H(1)R, and are 'non-drowsy' presumably due to reduced permeability through the blood-brain barrier. To characterize both histaminergic sleep regulation and the central actions of antihistamines, in the present study we analysed the effect of classic and modern antihistamines on rats' sleep using continuous i.c.v. infusions. EXPERIMENTAL APPROACH: Effects of classic (d-chlorpheniramine; d-CPA) and second-generation (cetirizine) antihistamines on sleep were compared after i.p. injections or continuous i.c.v. infusions into rats. Fluorescent cetirizine/DBD-pz was synthesized to trace the approximate distribution of cerebral cetirizine. Furthermore, the effects of H(1) R antagonists on cultured preoptic neurons were examined using calcium imaging. KEY RESULTS: d-CPA 4 mg·kg(-1) i.p. increased non-rapid eye movement (REM) sleep whereas 10-40 mg·kg(-1) d-CPA decreased non-REM sleep at dark onset time. Nocturnal i.c.v. infusions of d-CPA (10 µmol·100 µL(-1)·10 h(-1)) increased drowsiness but not non-REM sleep, whereas the same i.c.v. infusions of cetirizine significantly increased non-REM sleep, abolished REM sleep, and decreased wakefulness for more than 10 h. The medial preoptic area contained the greatest fluorescent labelling after i.c.v. cetirizine/DBD-pz infusions. Histamine-induced Ca(2+) increases in medial preoptic neurons were blocked by d-CPA or cetirizine, whereas d-CPA, but not cetirizine, increased Ca(2+) irrespective of antihistaminergic activity at ≥ 100 µM. CONCLUSION AND IMPLICATIONS: The excitatory action of d-CPA may explain the seemingly inconsistent actions of d-CPA on sleep. Cerebral H(1)R inhibition by cetirizine induces synchronization of cerebral activity and prolonged, continuous slow-wave sleep.