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Alzheimer's disease (AD), the leading disorder of memory impairment in our aging population, is increasing at an alarming rate. AD is currently identified by three 'gold standard criteria': (i) dementia in life, (ii) amyloid plaques at autopsy, and (iii) neurofibrillary tangles at autopsy. Several autopsy studies have indicated that dementia in life is a consequence of lost synaptic networks in the brain, while many clinical trials targeting neurotoxic amyloid beta (Aβ) have consistently failed to produce therapeutic effects on memory function in AD patients. Restoring cognitive function(s) by activating endogenous repairing/regenerating mechanisms that are synaptogenic and antiapoptotic (preventing neuronal death), however, is emerging as a necessary disease-modifying therapeutic strategy against AD and possibly for other degenerative dementias, such as Parkinson's disease and multi-infarct dementia.

Fragile X syndrome (FXS), an X-chromosome linked intellectual disability, is the leading monogenetic cause of autism spectrum disorder (ASD), a neurodevelopmental condition that currently has no specific drug treatment. Building upon the demonstrated therapeutic effects on spatial memory of bryostatin-1, a relatively specific activator of protein kinase C (PKC)ε, (also of PKCα) on impaired synaptic plasticity/maturation and spatial learning and memory in FXS mice, we investigated whether bryostatin-1 might affect the autistic phenotypes and other behaviors, including open field activity, activities of daily living (nesting and marble burying), at the effective therapeutic dose for spatial memory deficits. Further evaluation included other non-spatial learning and memory tasks. Interestingly, a short period of treatment (5 weeks) only produced very limited or no therapeutic effects on the autistic and cognitive phenotypes in the Fmr1 KO2 mice, while a longer treatment (13 weeks) with the same dose of bryostatin-1 effectively rescued the autistic and non-spatial learning deficit cognitive phenotypes. It is possible that longer-term treatment would result in further improvement in these fragile X phenotypes. This effect is clearly different from other treatment strategies tested to date, in that the drug shows little acute effect, but strong long-term effects. It also shows no evidence of tolerance, which has been a problem with other drug classes (mGluR5 antagonists, GABA-A and -B agonists). The results strongly suggest that, at appropriate dosing and therapeutic period, chronic bryostatin-1 may have great therapeutic value for both ASD and FXS.

Executive functioning is a high-level cognitive ability, regulating other abilities and behaviors to achieve desired goals. A typical executive task can be defined as the capacity to maintain one's attention on the current task, that is, responding only to the correct but not to distractive stimuli. Impairments of executive functions, or executive dysfunctions, have a growing impact on everyday life and academic achievement and are usually an early feature, and one of the core features, in brain injury and memory and behavioral disorders. Furthermore, emerging evidence indicates that memory therapeutics cannot achieve their clinical benefits in cognition if executive dysfunction is not effectively and simultaneously treated. Improvement of executive functions might be achieved through targeting some signaling pathways in the brain, including the brain-derived neurotrophic factor signaling pathways. These agents may be useful either as stand-alone interventions for patients with executive dysfunction and/or psychiatric and memory disorders or as essential adjuncts to drugs that target the underlying pathology in various brain injury and memory and behavioral disorders.

Despite over a half-century's intensive research worldwide, the currently available antidepressants remain sub-optimal. Therapeutic options for treatment-resistant depression, for instance, are rather limited. Here, we found that rats exhibited a lasting treatment-resistant depressive immobility in response to open space swim test at a high intensity of induction. The induced depressive behavior is associated with a dramatic impairment in spatial learning and memory. Both the depressive immobility and impairment in spatial learning and memory are sensitive to a period of chronic treatment with bryopstatin-1, a relatively selective activator of protein kinase Cε. Bryostatin-1-like analogues therefore might have therapeutic values for the treatment of treatment-resistant depression.

Bryostatin 1, a potent activator of protein kinase C epsilon (PKCɛ), has been shown to reverse synaptic loss and facilitate synaptic maturation in animal models of Alzheimer’s disease (AD), Fragile X, stroke, and other neurological disorders. In a single-dose (25 μg/m2) randomized double-blind Phase IIa clinical trial, bryostatin levels reached a maximum at 1-2 h after the start of infusion. In close parallel with peak blood levels of bryostatin, an increase of PBMC PKCɛ was measured (p = 0.0185) within 1 h from the onset of infusion. Of 9 patients with a clinical diagnosis of AD, of which 6 received drug and 3 received vehicle within a double-blind protocol, bryostatin increased the Mini-Mental State Examination (MMSE) score by +1.83±0.70 unit at 3 h versus –1.00±1.53 unit for placebo. Bryostatin was well tolerated in these AD patients and no drug-related adverse events were reported. The 25 μg/m2 administered dose was based on prior clinical experience with three Expanded Access advanced AD patients treated with bryostatin, in which return of major functions such as swallowing, vocalization, and word recognition were noted. In one Expanded Access patient trial, elevated PKCɛ levels closely tracked cognitive benefits in the first 24 weeks as measured by MMSE and ADCS-ADL psychometrics. Pre-clinical mouse studies showed effective activation of PKCɛ and increased levels of BDNF and PSD-95. Together, these Phase IIa, Expanded Access, and pre-clinical results provide initial encouragement for bryostatin 1 as a potential treatment for AD.

Fragile X syndrome (FXS) is characterized by synaptic immaturity, cognitive impairment, and behavioral changes. The disorder is caused by transcriptional shutdown in neurons of thefragile X mental retardation 1gene product, fragile X mental retardation protein. Fragile X mental retardation protein is a repressor of dendritic mRNA translation and its silencing leads to dysregulation of synaptically driven protein synthesis and impairments of intellect, cognition, and behavior, and FXS is a disorder that currently has no effective therapeutics. Here, young fragile X mice were treated with chronic bryostatin-1, a relatively selective protein kinase Cεactivator, which induces synaptogenesis and synaptic maturation/repair. Chronic treatment with bryostatin-1 rescues young fragile X mice from the disorder phenotypes, including normalization of most FXS abnormalities in 1) hippocampal brain-derived neurotrophic factor expression, 2) postsynaptic density-95 levels, 3) transformation of immature dendritic spines to mature synapses, 4) densities of the presynaptic and postsynaptic membranes, and 5) spatial learning and memory. The therapeutic effects were achieved without downregulation of metabotropic glutamate receptor (mGluR) 5 in the hippocampus and are more dramatic than those of a late-onset treatment in adult fragile X mice. mGluR5 expression was in fact lower in fragile X mice and its expression was restored with the bryostatin-1 treatment. Our results show that synaptic and cognitive function of young FXS mice can be normalized through pharmacological treatment without downregulation of mGluR5 and that bryostatin-1-like agents may represent a novel class of drugs to treat fragile X mental retardation at a young age and in adults.

Evidence is accumulating that many memory disorders, including those due to neurodegenerative diseases, traumatic brain injury (TBI), vascular disease, or abnormal brain development, share common features of memory-related pathology. Structural and functional deficits of synapses are at the core of the underlying pathophysiology, constituting a critical point of convergence in memory disorders. Memory therapeutics that target synaptic loss and dysfunction - that is, to slow, halt, or reverse progression of the disorders at the level of synapses, via synaptogenic molecular cascades such as those of protein kinase C (PKC) and brain-derived neurotrophic factor (BDNF) - possess universal therapeutic value for many forms of memory disorder. They may be useful either as standalone interventions for patients with memory disorders or as adjuncts to drugs that target the underlying pathology.

Fragile X syndrome (FXS) is caused by transcriptional silencing in neurons of the FMR1 gene product, fragile X mental retardation protein (FMRP), a repressor of dendritic mRNA translation. The lack of FMRP leads to dysregulation of synaptically driven protein synthesis and impairments of intellect, cognition, and behavior, a disorder that currently has no effective therapeutics. Fragile X mice were treated with chronic bryostatin-1, a relatively selective protein kinase ε activator with pharmacological profiles of rapid mGluR desensitization, synaptogenesis, and synaptic maturation/repairing. Differences in the major FXS phenotypes, synapses, and cognitive functions were evaluated and compared among the age-matched groups. Long-term treatment with bryostatin-1 rescues adult fragile X mice from the disorder phenotypes, including normalization of most FXS abnormalities in hippocampal brain-derived neurotrophic factor expression and secretion, postsynaptic density-95 levels, glycogen synthase kinase-3β phosphorylation, transformation of immature dendritic spines to mature synapses, densities of the presynaptic and postsynaptic membranes, and spatial learning and memory. Our results show that synaptic and cognitive function of adult FXS mice can be normalized through pharmacologic treatment and that bryostatin-1-like agents may represent a novel class of drugs to treat fragile X mental retardation even after postpartum brain development has largely completed.

Bryostatin 1, a potential anti-Alzheimer drug, is effective at subnanomolar concentrations. Measurement is complicated by the formation of low m/z degradation products and the formation of adducts with various cations, which make accurate quantitation difficult. Adduct formation caused the sample matrix or mobile phase to partition bryostatin 1 into products of different mass. Degradation of the 927 [M+Na]+ ion to a 869 m/z product was strongly influenced by ionization conditions. We validated a bryostatin 1 assay in biological tissues using capillary column HPLC with nanospray ionization (NSI) in a triple-quadrupole mass spectrometer in selected reaction monitoring (SRM) mode. Adduct formation was controlled by adding 1 mM acetic acid and 0.1 mM sodium acetate to the HPLC buffer, maximizing the formation of the [M+Na]+ ion. Efficient removal of contaminating cholesterol from the sample during solvent extraction was also critical. The increased sensitivity provided by NSI and capillary-bore columns and the elimination of signal partitioning due to adduct formation and degradation in the ionization source enabled a detection limit of 1 × 10−18 mol of bryostatin 1 and a LLOQ of 3 × 10−18 mol from 1 μl of sample. Bryostatin 1 at low pmol/l concentrations enabled measurement in brain and other tissues without the use of radioactive labels. Despite bryostatin 1's high molecular weight, considerable brain access was observed, with peak brain concentrations exceeding 8% of the peak blood plasma concentrations. Bryostatin 1 readily crosses the blood–brain barrier, reaching peak concentrations of 0.2 nM, and specifically activates and translocates brain PKCɛ.

The 'vascular depression' hypothesis has recently attracted significant research attention, although the causal relationship between vascular-related injuries and depression has not been established. Here, we show that one episode of cerebral ischemia was sufficient to greatly increase the sensitivity of rats to potentially depressogenic events, evaluated at below-threshold intensities in the open space swim test. The induced 'ischemic depression' was lasting and sensitive to an acute administration of brain-derived neurotrophic factor or bryostatin-1, a relatively selective activator of protein kinase Cε, during the induction phase. Chronic treatment with bryostatin-1 (5 weeks) after the induction of depressive behavior reversed the depressive immobility and produced a lasting therapeutic effect, which remained effective 3 weeks after discontinuation of the treatment. Similar treatment with alaproclate, a selective serotonin reuptake inhibitor, in contrast, produced temporary relief from the depressive symptoms, with the therapeutic effect disappearing soon after the end of the treatment. The results strongly suggest that cerebral ischemia has a direct role in shaping the sensitivity of an individual to depressogenic events and that bryostatin-1-like agents may be developed as therapeutics for treating ischemic depression in humans.

Global cerebral ischemia/hypoxia, as can occur during human stroke, damages brain neural networks and synaptic functions. The recently demonstrated protein kinase C (PKC) activation–induced synaptogenesis in rat hippocampus suggested the potential of PKC-mediated antiapoptosis and synaptogenesis during conditions of neurodegeneration. Consequently, we examined the effects of chronic bryostatin-1, a PKC activator, on the cerebral ischemia/hypoxia–induced impairment of synapses and neurotrophic activity in the hippocampal CA1 area and on hippocampus-dependent spatial learning and memory. Postischemic/hypoxic bryostatin-1 treatment effectively rescued ischemia-induced deficits in synaptogenesis, neurotrophic activity, and spatial learning and memory. These results highlight a neuroprotective signaling pathway, as well as a therapeutic strategy with an extended time window for reducing brain damage due to stroke by activating particular PKC isozymes.

Evidence is emerging that protein kinase C (PKC) plays a crucial role in the neural processing of memory information and that PKC deficits underlie certain types of memory impairment, including Alzheimer's dementia. Chronic activation of PKC isozymes with bryostatin-1 induces synthesis of the proteins that are involved in memory consolidation and, therefore, may represent a pharmacological strategy for antidementic and memory therapies. PKC isozymes are, however, sensitive to oxidants, whose generation is also increased by PKC activation. Oxidants may be responsible for some adverse effects with PKC activators, potentially limiting their antidementic and memory-enhancing "benefit". We investigated the effects of intravenous bryostatin-1, a potent PKC activator, and of its co-administration with oral alpha-tocopherol, a potent antioxidant, on spatial learning and memory. Bryostatin-1 at a chronic and intravenous dose of 10 microg/m2 (2 doses/week for 3 weeks) alone did not significantly affect the spatial learning and memory, but showed a synergistic effect when co-administered with alpha-tocopherol (60 IU/kg, orally and daily for 3 weeks), a potent lipid-soluble antioxidant and also a possible inhibitor of PKC in peripheral tissues. Acute administration of the same doses, however, did not have obvious influence on the learning and memory. These results provide support for the strategy of achieving memory-enhancing benefits with PKC activators and restricting their oxidant-related adverse effects with alpha-tocopherol co-administration. These agents, therefore, may hold significant potential as new, combined antidementic and memory therapeutics in the future.

Bryostatin‐1 is a powerful protein kinase C (PKC) agonist, activating PKC isozymes at nanomolar concentrations. Pharmacological studies of bryostatin‐1 have mainly been focused on its action in preventing tumor growth. Emerging evidence suggests, however, that bryostatin‐1 exhibits additional important pharmacological activities. In preclinical studies bryostatin‐1 has been shown at appropriate doses to have cognitive restorative and antidepressant effects. The underlying pharmacological mechanisms may involve an activation of PKC isozymes, induction of synthesis of proteins required for long‐term memory, restoration of stress‐evoked inhibition of PKC activity, and reduction of neurotoxic amyloid accumulation and tau protein hyperphosphorylation. The therapeutic potential of bryostatin‐1 as a CNS drug should be further explored.

Dementia and depression are clinical symptoms commonly associated in patients. Emerging evidence suggests that the two diseases share many profiles in their development and underlying neural/molecular mechanisms. Thus, interest is raised in developing new classes of antidepressant agents with activity of cognitive enhancement. Here, we show that bryostatin-1, a protein kinase C substrate activator, at bilateral intracerebroventricular doses of 0.64 or 2 pmol/site, significantly enhanced learning and memory of rats in a spatial water maze task. When applied at the doses at which it exhibits memory-enhancing activity, bryostatin-1 showed a significant antidepressant activity, as determined in an open space swim test. Both effects were not observed when a smaller dose was administered and were largely eliminated by co-administration of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), a protein kinase C inhibitor. These results support the hypothesis that memory processing and mood regulation share common neural mechanisms. Restoring impaired mood regulation with antidepressant agents that also exhibit memory-enhancing activity may represent one of the new strategies in the fight against depression associated with memory impairments.

Hypoxia significantly reduced cholinergic theta activity in rat CA1 field and intracellular theta in the CA1 pyramidal cells, recorded in hippocampal slices. The hypoxic responses of the hippocampal CA1 pyramidal cells to a brief hypoxia consisted of a short period of "synaptic arrest", observed as an elimination of excitatory postsynaptic current under voltage clamp and recovered immediately as oxygenation was reinitiated. The hypoxic synaptic arrest was not associated with reduced postsynaptic responses of the pyramidal cells to externally applied L-glutamate, suggesting that the synaptic arrest might result from a presynaptic mechanism. The hypoxic synaptic arrest was abolished in the presence of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a specific adenosine A(1) receptor antagonist. Blocking adenosine A(1) receptors also eliminated effects of hypoxia on the hippocampal CA1 field theta activity and intracellular theta of the CA1 pyramidal cells. In behaving rats, brief hypoxia impaired their water maze performance in both the escape latency and probe tests. The impairment was prevented by intralateral cerebroventricular injections of DPCPX. These results suggest that hypoxia releases adenosine and produces an inhibition of synaptic transmission and intracellular signal cascade(s) involved in generation/maintenance of hippocampal CA1 theta activity. This protection of synaptic efficacy and spatial learning through adenosine A(1) receptor antagonism may represent an effective therapeutic strategy to eliminate functional interruption due to transient hypoxic episodes and/or chronic hypoxia secondary to compromise of respiratory function.

Enhancement of memory acquisition and recall represents an important pharmacological goal in the treatment of cognitive disorders. In addition to its involvement in pH regulation, HCO3- reabsorption and CO2 expiration, carbonic anhydrase plays a crucial role in signal processing, long-term synaptic transformation and attentional gating of memory storage. Carbonic anhydrase dysfunction impairs cognition and is associated with mental retardation, Alzheimer's disease and aging. The pharmacological profile of carbonic anhydrase has been refined and specific activators have been developed. In this article, an integrated view of the involvement of carbonic anhydrase activity in synaptic plasticity and cognition will be presented, with particular focus on attentional gating of spatial learning and memory.

Stress in life is unavoidable, affecting everyone on a daily basis. Psychological stress in mammals triggers a rapidly organized response for survival, but it may also cause a variety of behavioral disorders and damage cognitive function. Stress is associated with biases in cognitive processing; some of the most enduring memories are formed by traumatic events. Our understanding of how cognition is shaped by stress is still relatively primitive; however, evidence is rapidly accumulating that the 'mature' brain has a great capacity for plasticity and that there are numerous ways through which pharmacological therapeutics could rescue cognitive function and regain cognitive balance. In this review, we discuss recent advances in our understanding of the interplay between stress and cognitive processes and potential therapeutic approaches to stress-related behavioral and cognitive disorders.

Members of the N -methyl- d -aspartate (NMDA) class of glutamate receptors (NMDARs) are critical for development, synaptic transmission, learning and memory; they are targets of pathological disorders in the central nervous system. NMDARs are phosphorylated by both serine/threonine and tyrosine kinases. Here, we demonstrate that cyclin dependent kinase-5 (Cdk5) associates with and phosphorylates NR2A subunits at Ser-1232 in vitro and in intact cells. Moreover, we show that roscovitine, a selective Cdk5 inhibitor, blocks both long-term potentiation induction and NMDA-evoked currents in rat CA1 hippocampal neurons. These results suggest that Cdk5 plays a key role in synaptic transmission and plasticity through its up-regulation of NMDARs.

Oxygenation of cells and tissues in mammals according to metabolic needs is always a life-or-death necessity. Over the last decade, life scientists have gained an impressive understanding of cellular and molecular mechanisms in hypoxic-ischemic injury and memory deficits, survival, and death. Functional recovery from hypoxia-ischemia depends on how the individual responds to the insult, and whether appropriate responses are initiated and maintained. Unraveling the biochemical and molecular mechanisms and responses of hypoxia-ischemia is likely to dramatically shape and improve medical practice in the treatments of hypoxia-ischemia and memory deficits.

Encoding an experience into a lasting memory is thought to involve an altered operation of relevant synapses and a variety of other subcellular processes, including changed activity of specific proteins. Here, we report direct evidence that co-applying (associating) membrane depolarization of rat hippocampal CA1 pyramidal cells with intracellular microinjections of calexcitin (CE), a memory-related signaling protein, induces a long-term transformation of inhibitory postsynaptic potentials from basket interneurons (BAS) into excitatory postsynaptic potentials. This synaptic transformation changes the function of the synaptic inputs from excitation filter to amplifier, is accompanied by a shift of the reversal potential of BAS–CA1 postsynaptic potentials, and is blocked by inhibiting carbonic anhydrase or antagonizing ryanodine receptors. Effects in the opposite direction are produced when anti-CE antibody is introduced into the cells, whereas heat-inactivated CE and antibodies are ineffective. These data suggest that CE is actively involved in shaping BAS–CA1 synaptic plasticity and controlling information processing through the hippocampal networks.

Long-term potentiation (LTP) in the hippocampal slice preparation has been proposed as an in vitro model for long-term memory. However, correlation of LTP with memory in living animals has been difficult to demonstrate. Furthermore, in the last few years evidence has accumulated that dissociate the two. Because potassium channels might determine the weight of synapses in networks, we studied the role of Kv1.4, a presynaptic A-type voltage-dependent K + channel, in both memory and LTP. Reverse transcription–PCR and Western blot analysis with specific antibodies showed that antisense oligodeoxyribonucleotide to Kv1.4 microinjected intraventricularly into rat brains obstructed hippocampal Kv1.4 mRNA, “knocking down” the protein in the hippocampus. This antisense knockdown had no effect on rat spatial maze learning, memory, or exploratory behavior, but eliminated both early- and late-phase LTP and reduced paired-pulse facilitation (a presynaptic effect) in CA1 pyramidal neurons without affecting dentate gyrus LTP. This presynaptic Kv1.4 knockdown together with previous postsynaptic Kv1.1 knockdown demonstrates that CA1 LTP is neither necessary nor sufficient for rat spatial memory.

The protein kinase C (PKC) isoforms, which play an essential role in transmembrane signal conduction, can be viewed as a family of "memory kinases." Evidence is emerging that they are critically involved in memory acquisition and maintenance, in addition to their involvement in other functions of cells. Deficits in PKC signal cascades in neurons are one of the earliest abnormalities in the brains of patients suffering from Alzheimer's disease. Their dysfunction is also involved in several other types of memory impairments, including those related to emotion, mental retardation, brain injury, and vascular dementia/ischemic stroke. Inhibition of PKC activity leads to a reduced capacity of many types of learning and memory, but may have therapeutic values in treating substance abuse or aversive memories. PKC activators, on the other hand, have been shown to possess memory-enhancing and antidementia actions. PKC pharmacology may, therefore, represent an attractive area for developing effective cognitive drugs for the treatment of many types of memory disorders and dementias.

1. In anaesthetized rats, extracellular and intracellular recordings were made from 119 respiratory neurones in the rostroventrolateral reticular nucleus (RVL) of the medulla oblongata. 2. Two types of active respiratory neurones were detected in RVL: expiratory (E) and pre-inspiratory (Pre-I), based on the relationship between their discharge and that of the phrenic nerve. Some Pre-I but none of the E neurones could be antidromically excited from the C(3)-C(4) level of the spinal cord. 3. E and Pre-I neurones of RVL were excited by stimulation of the arterial chemoreceptors by a close arterial injection of sodium cyanide. The reflex excitation of RVL E neurones was preceded by increased phrenic nerve activity, while the excitation of RVL Pre-I neurones preceded the increases in phrenic nerve activity. 4. The chemoreflex excitation of the two types of RVL respiratory neurones as well as their resting discharge was abolished or significantly depressed by microionophoresis of kynurenate, a wide-spectrum antagonist of excitatory amino acid receptors, while xanthurenate, an inactive analogue of kynurenate, was without effect. 5. In ventilated rats, bilateral microinjection into RVL of kynurenate, but not xanthurenate, abolished resting activity and chemoreflex excitation of phrenic nerve activity, whilst in spontaneously breathing rats, kynurenate microinjection into RVL produced apnea and silenced phrenic nerves. 6. We conclude: (a) chemoreflex excitation of the phrenic nerves is mediated by stimulating Pre-I neurones of RVL by excitatory amino acidergic inputs and (b) RVL Pre-I neurones may directly and/or indirectly excite spinal phrenic motor neurones and hence are involved in inspiratory rhythmogenesis.

In pentobarbital sodium-anesthetized, paralyzed, and ventilated rats, systemic hypoxia, produced by intratracheal N2 administration for 20 s, rapidly increased activities of reticulospinal vasomotor neurons in the rostroventolateral reticular nucleus (RVL) of the medulla oblongata (by 23.9 +/- 4.7 spikes/s) and sympathetic nerves (by 30.9 +/- 4.7 microV) and arterial pressure (by 35.6 +/- 6.4 mmHg). The sympathoexcitatory and pressor responses were abolished by bilateral microinjections of muscimol, a gamma-aminobutyric acid (GABA)A-receptor agonist, (250 pmol per 50 nl/site) into the RVL. Chemical inhibition of RVL also reduced arterial pressure to 48.1 +/- 3.7 mmHg and eliminated sympathetic nerve activity. Intravenous infusion of L-phenylephrine and intrathecal administration of kainic acid restored arterial pressure to control level but not the rapid sympathoexcitatory responses to acute hypoxia. We conclude that, in pentobarbital-anesthetized rats, the sympathetic vasomotor tone and pressor responses to acute hypoxia depend on activity and excitation of RVL-spinal vasomotor neurons. The neural mechanisms responsible for the sympathetic tone and rapid pressor responses to hypoxia in these animals qualitatively differ neither from those anesthetized with urethan nor from the decerebrate unanesthetized animals.

In anesthetized rats, stimulation of the arterial chemoreceptors excites reticulospinal vasomotor neurons of the nucleus rostroventrolateral reticularis of the medulla oblongata, via activating the neuronal NMDA receptors. Excitation of these neurons is responsible for reflex increases in sympathetic neuronal activity and arterial pressure. Additional doses (0.12–0.24 g/kg, i.v.) of urethane dose-dependently reduced the elevations in the discharge rate of reticulospinal vasomotor and sympathetic neurons and of arterial pressure, elicited by stimulating the carotid chemoreceptors with intra-carotid injections of sodium cyanide (100 nmol/10 μl), without affecting discharges of the carotid chemoafferents. Microiontophoresis of urethane onto the reticulospinal vasomotor neurons reversibly inhibited the excitation elicited by stimulation of the chemoreceptors and by iontophoretically applied L -glutamate. The results indicate that the suppression of chemoreflexes by excessive amount of urethane is central and one of its actions is blocking excitatory amino acid transmission onto these vasomotor neurons.

The past decade has witnessed rapid progress in defining neural circuits and mechanisms in the brain, responsible for regulation of the sympathetic nerve activity and cardiovascular functions. Several groups of cardiovascular neurons in the brainstem form the fundamental neural circuits, through which reflexly and centrally initiated sympathetic responses are processed. Their interplay determines the levels of sympathetic nerve activity and vascular tone. Substantial evidence indicates that a small population of reticulospinal vasomotor neurons in the rostroventrolateral reticular nucleus of the medulla oblongata play critical and integrative roles by: 1) providing, largely by their intrinsic pacemaker activity, tonic sympathoexcitation, thus maintaining normal blood pressure and organ blood flows, 2) mediating a variety of circulatory reflexes and centrally initiated sympathetic responses thereby helping to match organ blood flow to metabolic demands, and 3) acting as intrinsic oxygen detectors which orchestrate appropriate autonomic response programs to protect the integrity of brain in response to acute hypoxia-ischemia. Elaboration of the neural mechanisms and cellular and molecular properties of these vasomotor neurons related to dynamic regulation of the cardiovascular system in normal and disease states will be of relevance to a full appreciation of their role in adaptation of the organism to its internal and external environments and to the development of strategies to fight against neurogenic cardiovascular diseases and to restore normal functions.

In vitro, clonidine (1, 10, or 30 microM) dose-dependently and reversibly inhibited tonically active pacemaker neurons that correspond to the relatively fast-conducting reticulospinal vasomotor neurons of the rostral ventrolateral reticular nucleus of the medulla oblongata in rats. The clonidine-induced membrane-hyperpolarizing response of these neurons was abolished by either tetrodotoxin, bicuculline, a GABAA receptor antagonist, or 4,4'-diisothiocyano-1,2'-disulphonic stilbene acid, a Cl- channel blocker. We conclude that the clonidine-induced inhibition of the pacemaker neurons of the rostral ventrolateral reticular nucleus is indirect, mediated by synaptic release of gamma-aminobutyric acid (GABA) or GABA-like substances, which activate Cl- channels of the pacemaker neurons of the rostral ventrolateral reticular nucleus.

Memories are much more easily impaired than improved. Dementias, a lasting impairment of memory function, occur in a variety of cognitive disorders and become more clinically dominant as the population ages. Protein kinase C is one of the "cognitive kinases," and plays an essential role in both memory acquisition and maintenance. Deficits in protein kinase C (PKC) signal cascades in neurons represent one of the earliest changes in the brains of patients with Alzheimer's disease (AD) and other types of memory impairment, including those related to cerebral ischemia and ischemic stroke. Inhibition or impairment of PKC activity results in compromised learning and memory, whereas an appropriate activation of certain PKC isozymes leads to an enhancement of learning and memory and/or antidementic effects. In preclinical studies, PKC activators have been shown to increase the expression and activity of PKC isozymes, thereby restoring PKC signaling and downstream activity, including stimulation of neurotrophic activity, synaptic/structural remodeling, and synaptogenesis in the hippocampus and related cortical areas. PKC activators also reduce the accumulation of neurotoxic amyloid and tau protein hyperphosphorylation and support anti-apoptotic processes in the brain. These observations strongly suggest that PKC pharmacology may represent an attractive area for the development of effective cognition-enhancing therapeutics for the treatment of dementias.

In anesthetized, paralyzed, and ventilated rats, hypoxia or intracarotid cyanide excited the carotid chemoafferents, whereas intracarotid dopamine and tyramine inhibited the chemoafferent discharges. The inhibition was abolished by chlorpromazine without attenuating the hypoxic excitation. Comparably, the hypoxic excitation was not attenuated by the following: 1) inhibition of nitric oxide synthase with NG-nitro-L-arginine; 2) inhibition of heme oxygenase with zinc protoporphyrin IX; 3) antagonism of ATP receptors with reactive blue 2; 4) antagonism of cholinergic receptors with atropine or trimethaphan; 5) inactivation of adenosine with adenosine deaminase; and 6) blockade of glutamate receptors with kynurenate. Systemic administration of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N'N'-tetraacetic acid, in doses reversibly blocking sympathetic ganglionic transmission, was also without effect. Cyanide microinjection (0.05-0.5 nmol) into the petrosal but not nodose ganglion elicited a rapid dose-dependent elevation of arterial pressure. We conclude that excitation of the chemoreceptor afferents by hypoxia/cyanide cannot be attributed to release of these agents nor to others by Ca(2+)-dependent mechanisms. The results suggest that the afferent nerves themselves might function as oxygen detectors.

In peripherally chemodenervated anesthetized and ventilated rats, inhalation of 100% N 2 for 20 s rapidly excites reticulospinal vasomotor neurons of the rostroventrolateral reticular nucleus (RVL) and sympathetic nerves. After an initial fall, arterial pressure is also elevated. The sympathoexcitatory response and secondary increases in arterial pressure were abolished by microinjections of muscimol (250 pmol) into the RVL or by intrathecal administration of kynurenate (500 nmol), a broad-spectrum antagonist of excitatory amino acid receptors, but not by benextramine, an α-adrenoceptor antagonist. The results indicate that excitation of pre-ganglionic sympathetic neurons in the spinal cord by hypoxia results from excitation of RVL-spinal vasomotor neurons, probably the glutamatergic neurons.

We examined whether rapid sympathoexcitatory responses to hypoxia in rats resulting from excitation of reticulospinal vasomotor neurons of rostral ventrolateral medulla (RVL) results from activation of protein kinase C. In peripherally chemodenervated rats, the specific phosphokinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) administered intracisternally (i.c., 1 mumol), abolished responses of medullary vasomotor neurons and sympathetic nerves to baroreceptor activation, but did not attenuate excitation of RVL or sympathetic neurons to systemic hypoxia (100% N2 for 20 s). Responses of the vasomotor neurons to iontophoretically applied GABA were not attenuated by H-7. In slices, arachidonic acid (100 microM, 40 s) did not change membrane currents (VH = -70 mV) of RVL neurons in the presence tetrodotoxin (10 microM). The inward membrane currents (0.49 nA) induced by cyanide (300 microM, 40 s) were not reduced by H-7 (100 microM, 20 min). The results indicate that activation of protein kinase C does not underlie mechanisms involved in rapid hypoxic excitation of reticulospinal vasomotor neurons.

Systemic hypoxia [PaO2 27.3 +/- 1.8 (SE) mmHg] in anesthetized paralyzed rats reversibly increased within seconds the arterial pressure and activities of the sympathetic nerves and the reticulospinal vasomotor neurons of the rostral ventrolateral medulla (RVL). After peripheral chemodenervation, hypoxia also increased activity of the sympathetic nerves and doubled discharges of the vasomotor neurons while inhibiting a majority of the RVL respiratory neurons. Systemic hypercapnia was not effective in eliciting sympathoexcitatory responses. Iontophoresis of sodium cyanide stimulated the vasomotor and inhibited the respiratory neurons. In contrast, iontophoreses of H+, HCO3-, and lactate were without effects on activity of the vasomotor neurons. We conclude 1) hypoxia excites the vasomotor neurons by activating the arterial chemoreceptors and by activating intrinsic cellular mechanisms probably unrelated to accumulation of metabolic byproducts; 2) hypoxia may be the adequate stimulus exciting the RVL-spinal vasomotor and inhibiting the respiratory neurons during the cerebral ischemic response; and 3) these vasomotor neurons may be central oxygen detectors.

Among the pathologic hallmarks of Alzheimer's disease (AD) neurodegeneration, only synaptic loss in the brains of AD patients closely correlates with the degree of dementiain vivo. Here, we describe a molecular basis for this AD loss of synapses: pathological reduction of synaptogenic PKC isozymes and their downstream synaptogenic substrates, such as brain-derived neurotrophic factor. This reduction, particularly of PKC α and ε, occurs in association with elevation of soluble β amyloid protein (Aβ), but before the appearance of the amyloid plaques or neuronal loss in the Tg2576 AD transgenic mouse strain. Conversely, treatment of the Tg2576 mouse brain with the PKC activator, bryostatin-1, restores normal or supranormal levels of PKC α and ε, reduces the level of soluble Aβ, prevents and/or reverses the loss of hippocampal synapses, and prevents the memory impairment observed at 5 months postpartum. Similarly, the PKC ε-specific activator, DCP-LA, effectively prevents synaptic loss, amyloid plaques, and cognitive deficits (also prevented by bryostatin-1) in the much more rapidly progressing 5XFAD transgenic strain. These results suggest that synaptic loss and the resulting cognitive deficits depend on the balance between the lowering effects of Aβ on PKC α and ε versus the lowering effects of PKC on Aβ in AD transgenic mice.

Ischemic-hypoxic neuro-excitation and toxicity have been attributed to a rapid release of glutamate and formation of nitric oxide. We have now demonstrated that sympatho-excitatory response (1.2-fold increase in sympathetic nerve activity) induced by intratracheal administration of 100% N2 for 20 s in anesthetized rats and membrane inward currents (0.4-0.5 nA) induced by cyanide (300 microM) and hypoxia (saturated with 75% N2) of these neurons recorded in slices of rat rostral ventrolateral medulla were neither reduced by blocking glutamate receptors with kynurenate, synaptic transmission with tetrodotoxin nor by inhibiting nitric oxide synthase with N-nitro-L-arginine, indicating that glutamate, synaptic inputs, and nitric oxide are not involved in rapid responses of reticulospinal vasomotor neurons to hypoxia.

Responses of reticulospinal vasomotor neurons, recorded in the rostral ventrolateral reticular nucleus of the medulla oblongata, to γ-aminobutyric acid (GABA) and cyanide microiontophoreses were examined during H + iontophoresis in anesthetized rats. Extracellular H + iontophoresis attenuated GABA-evoked decreases and enhanced cyanide-induced increases in the neuronal activity, but had no effect on the neuronal activity when applied alone. Opposite responses were produced during OH − iontophoresis. Similar effects were also observed on the glycine-evoked inhibition of these neurons during H + and OH − iontophoreses, suggesting that H + modulation of the GABA-evoked inhibition may not result from a specific action at the GABA receptor-channel complex. It is concluded that extracellular H + ions exert a modulatory action on responses of the reticulospinal vasomotor neurons to other neuro-active substances and may significantly contribute to hypoxic-ischemic cardiovascular regulation.

Evidence is accumulating indicating that some protein kinase C (PKC) isozymes play an essential role in various phases as well as types of learning and memory. Abnormal functions of PKC signal cascades in the brains have been found to represent one of the earliest changes in patients with Alzheimer's disease (AD) and other types of memory deficits, including those related to cerebral ischemic/stroke events. In preclinical studies, an inhibition or impairment of PKC activity leads to compromised learning and memory, whereas an appropriate activation of some PKC isozymes results in an enhancement of learning and memory and/or antidementic effects against memory disorders. PKC activators not only increase activity of PKC isozymes and thereby restore PKC signaling activity, including neurotrophic activity, synaptic/structural remodeling, and synaptogenesis in the hippocampus and related cortical areas, but also reduce the accumulation of neurotoxic amyloid and tau protein hyperphosphorylation in the brain. These observations strongly suggest that PKC isoform pharmacology may represent an attractive area for the development of cognition-enhancing agents and therapeutics against memory loss in the future.

In anesthetized rats, iontophoretic application of ATP excited the spinal cord-projection neurons in the rostral ventrolateral reticular nucleus of the medulla oblongata. The neuronal response to ATP was mimicked and then blocked by α,β-methylene-ATP, a metabolically stable ATP analogue, and the response was abolished by suramin. Microinjections of ATP (3–100 pmol) into the rostral ventrolateral medulla produced a powerful pressor response. The results suggest that ATP may function as a neurotransmitter or neuromodulator involved in medullary regulation of cardiovascular functions.

Inositol hexakisphosphate (IP6) was microinjected into the rostral venttrolateral reticular nucleus or iontophoresed onto reticulospinal sympathoexcitatory neurons of the nucleus in anesthetized rats. IP6 (5–500 pmol) induced a dose-dependent potent and prolonged elevation of arterial pressure which was mimicked by microinjection of ethyleneglycol-bis (β-aminoethylether) N,N,N′,N′-tetraacetic acid (EGTA), while myo-inositol was ineffective. Iontophoretic application of IP6 and EGTA excited the medullary sympathoexcitatory neurons but myo-inositol had no effect. Ihe effect of IP6 on firing rate of the sympathoexcitatory neurons was abolished by co-administration of Ca2+ ions onto these neurons. The results indicate that IP6 acts extracellularly to excite the medullary sympathoexcitatory neurons. The excitatory actions of IP6 may depend, at least in part, on a calcium-chelating action. Chelation of extracellular Ca2+ might be a physiological action of IP6.

Systemic hypoxia, produced in deeply anesthetized, paralyzed rats in which arterial chemoreceptors were denervated, elicited a decrease in arterial pressure (AP) averaging {minus}47 mmHg. Systemic administration of N{sup G}-nitro-L-arginine (L-NO{sub 2}Arg), inhibitor of nitric oxide (NO) synthase, attenuated the hypoxic depressor response by 79% and elevated AP by 21 mmHg. The effects of L-NO{sub 2}Arg on the hypoxic depressor response and arterial pressure were reversed by systemic administration of L- but not D-arginine. Elevation of AP with arginine-vasopressin or reduction of AP with nitroprusside to the pre-L-NO{sub 2}Arg levels did not modify the fall of AP to hypoxia. Endogenous NO synthesized in vivo from L-arginine, mediates most of the hypoxia depressor response.

The last decade has witnessed a rapid progress in understanding of the molecular cascades that may underlie memory and memory disorders. Among the critical players, activity of protein kinase C (PKC) isoforms is essential for many types of learning and memory and their dysfunction, and is critical in memory disorders. PKC inhibition and functional deficits lead to an impairment of various types of learning and memory, consistent with the observations that neurotoxic amyloid inhibits PKC activity and that transgenic animal models with PKCbeta deficit exhibit impaired capacity in cognition. In addition, PKC isozymes play a regulatory role in amyloid production and accumulation. Restoration of the impaired PKC signal pathway pharmacologically results in an enhanced memory capacity and synaptic remodeling / repair and synaptogenesis, and, therefore, represents a potentially important strategy for the treatment of memory disorders, including Alzheimer's dementia. The PKC activators, especially those that are isozyme-specific, are a new class of drug candidates that may be developed as future memory therapeutics.

Therapeutics for cerebral ischemia/hypoxia, which often results in ischemic stroke in humans, are a global unmet medical need. Here, we report that bryostatin-1, a highly potent protein kinase C (PKC) activator, interrupts pathophysiological molecular cascades and apoptosis triggered by cerebral ischemia/hypoxia, enhances neurotrophic activity, and induces synaptogenesis in rats. This postischemic therapeutic approach is further shown to preserve learning and memory capacity even 4 months later as well as long-term memory induced before the ischemic event. Our results of electromicroscopic and immunohistochemical analyses of neuronal and synaptic ultra-structure are consistent with a PKC-mediated synaptic remodeling and repair process that confers long-lasting preservation of spatial learning and memory before and after the cerebral ischemic/hypoxic event, suggesting a previously undescribed therapeutic modality for cerebral ischemia/hypoxia and ischemic stroke.

Neurons with regular ongoing activity attributable to intrinsic pacemaker properties were recorded in coronal tissue slices within the nucleus reticularis rostroventrolateralis of the rat medulla oblongata (RVL). The cells were injected with horseradish peroxidase or Lucifer yellow and their dendritic and proximal axonal characteristics were investigated (n = 15). These small-to-medium-sized neurons had a simple dendritic arborization (3-6 primary dendrites branching up to 3 times) apparently confined within the limits of nucleus RVL and with limited extension in the rostrocaudal direction. Their axons originated either from the cell body or from a primary dendrite and coursed in a dorsomedial direction without giving rise to local arborizations. It is concluded that RVL pacemaker neurons, presumed to represent a non-adrenergic class of sympathoexcitatory premotor neurons, exhibit characteristics reminiscent of the archetypal 'reticular core' neurons.

Effects of age on depression vulnerability and antidepressant efficacy remain an important concern. Here, we show, by using a novel animal model of depressive behavior, that young rats (4 weeks old) are more vulnerable to the induction of depressive behavior than older ones (3, 6, and 14 months old). The induced depressive behavior in different ages of rats, however, was similarly sensitive to imipramine. A direct cerebroventricular administration of brain-derived neurotrophic factor was also sufficient to produce an antidepressant-like effect in the rats of different ages. These results suggest that although different ages of rats exhibit different sensitivity to the induction of depressive behavior, the induced depressive behavior may involve the same type of underlying abnormal neuropathophysiology in the brain and is sensitive to imipramine and brain-derived neurotrophic factor treatment.

Emerging evidence suggests that dementia and depression, two clinical symptoms commonly associated, share the disorder of neuroplasticity in their neural/molecular pathology. Maintenance of sufficient neurostructural remodelling/neurotrophic activity may be central to cognition/antidementia and a balanced mood. Here, we show that intra-cerebroventricular (i.c.v.) 4-methylcatechol (4-MC), a stimulator of brain-derived neurotrophic factor (BDNF) expression and an indirect PKC activator significantly enhanced spatial learning and memory in rats and produced an antidepressant effect. Both effects were eliminated by co-administration of function-blocking anti-BDNF antibody. These results further support the hypothesis that memory processing and mood regulation share common mechanisms and thus therapeutic targets. BDNF enhancers may represent one of the new drug strategies in the fighting against depression associated with memory impairments.

This study explores the mechanism of action of catecholamines on rostral medullary pacemaker neurons with putative sympathoexcitatory function, in tissue slices. The firing rate of the pacemaker neurons of nucleus reticularis rostroventrolateralis (RVL pacemakers) was reversibly increased by agents which elevate intracellular levels of cAMP (forskolin and 8-br-cAMP). Forskolin dideoxy, an analog without action on adenylate cyclase, was ineffective and adenosine, a potential degradation product of 8-br cAMP produced inhibition exclusively and only in high doses (0.1-1 mM). The firing rate of these cells was uniformly increased by epinephrine and isoproterenol (10 microM) but unaffected by both phenylephrine (100 microM) and clonidine (up to 1 microM). These effects were abolished by pretreatment with the beta-adrenoceptor antagonist propranolol (10 microM) but they were unaffected by the alpha-antagonist phentolamine (100 microM). The indirectly-acting sympathomimetic amine tyramine (0.1-1 mM) activated all the cells tested. The effect of tyramine was antagonized by the beta-blocker pindolol and was absent 7 days after microinjection of the neurotoxin 6-hydroxydopamine into the lateral aspect of the RVL. Intracellular recordings indicated that both isoproterenol and tyramine enhanced the rate of depolarization of the pacemaker neurons during the interspike interval and produced a decrease in input resistance. After tetrodotoxin (TTX) pretreatment, isoproterenol produced a depolarization also associated with a reduction in input resistance. Three conclusions are proposed. First, RVL pacemakers have functional beta-adrenergic receptors whose activation increases their discharge rate via the intracellular production of cAMP. The effect of cAMP is due at least in part to the activation of an inward current which may be carried by a cation. Secondly, RVL neurons are in close proximity to a releasable pool of catecholamines which is susceptible to destruction by the cytotoxic agent 6-hydroxydopamine (6-OHDA). Finally it is tentatively suggested that the reduction in sympathetic tone produced by centrally acting beta-blockers could be due, at least in part, to an action of these agents on RVL pacemaker cells.

Protein kinase C (PKC) is involved in synaptic remodeling, induction of protein synthesis, and many other processes important in learning and memory. Activation of neuronal protein kinase C correlates with, and may be essential for, all phases of learning, including acquisition, consolidation, and reconsolidation. Protein kinase C activation is closely tied to hydrolysis of membrane lipids. Phospholipases C and A2 produce 1,2-diacylglycerol and arachidonic acid, which are direct activators of protein kinase C. Phospholipase C also produces inositol triphosphate, which releases calcium from internal stores. Protein kinase C interacts with many of the same pathways as insulin; therefore, it should not be surprising that insulin signaling and protein kinase C activation can both have powerful effects on memory storage and synaptic remodeling. However, investigating the possible roles of insulin in memory storage can be challenging, due to the powerful peripheral effects of insulin on glucose and the low concentration of insulin in the brain. Although peripheral for insulin, synthesized in the beta-cells of the pancreas, is primarily involved in regulating glucose, small amounts of insulin are also present in the brain. The functions of this brain insulin are inadequately understood. Protein kinase C may also contribute to insulin resistance by phosphorylating the insulin receptor substrates required for insulin signaling. Insulin is also responsible insulin-long term depression, a type of synaptic plasticity that is also dependent on protein kinase C. However, insulin can also activate PKC signaling pathways via PLC gamma, Erk 1/2 MAP kinase, and src stimulation. Taken together, the available evidence suggests that the major impact of protein kinase C and its interaction with insulin in the mature, fully differentiated nervous system appears to be to induce synaptogenesis, enhance memory, reduce Alzheimer's pathophysiology, and stimulate neurorepair.

The existence of links between Alzheimer's disease and diabetes is an important topic currently under active debate. Establishing such links if they exist and defining their common pathogenesis and pathophysiological mechanisms may lead to new concepts and research directions for the pharmacological treatment of Alzheimer's disease and diabetes. Alzheimer's disease is associated with peripheral and central insulin abnormalities. Cognitive capacities are often impaired in patients with diabetes. There are many mechanisms by which insulin-signaling abnormalities may affect clinical and pathological outcome of Alzheimer's disease. Insulin resistance and dysregulation of the degradation of neurotoxic amyloid and insulin appear at the core of the links between Alzheimer's disease and diabetes. Functions and expression of insulysin, an enzyme involved in the degradation of neurotoxic amyloid peptides and insulin, are usually impaired or reduced in Alzheimer's disease and diabetes. The increased occurrence of insulin resistance in Alzheimer's disease suggests that improving insulin effectiveness and insulysin activity may have therapeutic value in Alzheimer's disease patients and therefore is worth intensive investigation.

PKC plays an important role in many types of learning and memory. Evidence has been provided that PKC activation and translocation are induced in associative learning tasks. PKC inhibition, on the other hand, impairs learning and memory, consistent with the observations that transgenic animal models with a particular PKC isoform deficit exhibit impaired capacity in cognition. The dramatic impact of PKC pharmacology on learning and memory is further emphasized by a regulatory role of PKC isozymes in amyloid production and accumulation. Recent study reveals that PKC activation greatly reduces neurotoxic amyloid production and accumulation. PKC activators, therefore, may have important therapeutic values in the treatment of dementia, especially when fine-tuning of selective isoform activity can be effectively achieved pharmacologically, with further development of isozymes-specific agents. The success of antidementia therapy with agents that act on PKC signaling cascades depends on whether such agents at their effective doses would significantly disrupt or interfere with other vital functions that rely on a narrow range of PKC activities.

Vulnerability of females to depression among humans has not previously been reflected in animal models. Here, we show, by using a novel animal model of depression, that young female Wistar rats are clearly more vulnerable to depression induction than the males. This differential female vulnerability follows estrous cycle stages, is associated with cognitive impairment, and can be markedly transformed with sex hormones. Male hormone reduces vulnerability in females, whereas female hormone increases vulnerability in males. The induced depressive behavior in both sexes, however, is sensitive to imipramine and to the antagonism of the glucocorticoid receptors within a hormonal pathway previously implicated in human depression. Anisomycin, a protein synthesis inhibitor, eliminates the antidepressive effects of both antidepressants and male hormone but does not affect depression induction and estradiol-induced higher vulnerability. Moreover, direct cerebroventricular administration of brain-derived neurotrophic factor (BDNF), whose mRNA levels in the hippocampus and frontal cortex reach its lowest levels when estrogen levels are highest, is sufficient to rescue the antidepressive effects in the presence of the protein synthesis inhibitor. A selective enhancement of BDNF expression and/or BDNF signal cascades in the neural circuits controlling mood may represent an effective strategy for the development of novel antidepressants for both sexes, whereas blocking the gender-related higher vulnerability to potentially depressogenic events may lead to the development of specific antidepressants for the females.