The modulatory role of serotonin-1A receptors of the basolateral amygdala and dorsal periaqueductal gray on the impact of hormonal variation on the conditioned fear response.

Despite significant advances in the study of fear and fear memory formation, little is known about fear learning and expression in females. This omission has been proven surprising, as normal and pathological behaviors are highly influenced by ovarian hormones, particularly estradiol and progesterone. In the current study, we investigated the joint influence of serotonin (5-HT) neurotransmission and estrous cycle phases (low or high levels of estradiol and progesterone) on the expression of conditioned fear in a group of female rats that were previously divided according to their response to stressful stimuli into low or high anxiety-like subjects. The baseline amplitude of the unconditioned acoustic startle responses was high in high-anxiety female rats, with no effect on the estrous cycle observed. Data collected during the proestrus-estrus phase revealed that low-anxiety rats had startle amplitudes similar to those of high-anxiety rats. It is supposed that high-anxiety female rats benefit from increased estradiol and progesterone levels to achieve comparable potentiated startle amplitudes. In contrast, female rats experienced a significant decrease in hormone levels during the Diestrus phase. This decrease is believed to play a role in preventing them from displaying a heightened startle response when faced with strongly aversive stimuli. Data collected after 5-HT and 8-OH-DPAT were administered into the basolateral nuclei and dorsal periaqueductal gray suggest that 5-HT neurotransmission works with progesterone and estrogen to reduce startle potentiation, most likely by activating the serotonin-1A receptor subtype.

Prepulse inhibition based grouping of rats and assessing differences in response to pharmacological agents.

Schizophrenia modeling by disrupting prepulse inhibition (PPI) is one of the most frequently used psycho-pharmacological methods by administering pharmacological agents to stimulate disruption. However, since PPI is also a biological indicator of schizophrenia, it is possible to classify subjects based on their basal PPI values and group them as "low inhibition" and "high inhibition without taking any pharmacological agent. Therefore this study was conducted to show that rats can be divided into groups in terms of susceptibility to schizophrenia according to basal PPI values. It was also observed that these groups might give different responses to different pharmacological agents (apomorphine, amphetamine, MK-801, scopolamine, nicotine, caffeine). Male Sprague Dawley rats (250-350 g) were used in the study. To examine the effects of different pharmacological agents on the groups, apomorphine (0.5 mg/kg and 1 mg/kg), amphetamine (4 mg/kg), MK-801 (0.05 mg/kg and 0.15 mg/kg), scopolamine (0.4 mg/kg), nicotine (1 mg/kg) and caffeine (10 mg/kg and 30 mg/kg) were used. Amphetamine showed a disruptive effect on PPI in both low and high inhibitory groups, while apomorphine, MK-801, scopolamine, and nicotine showed PPI decrease only in the high inhibitory group. Besides, caffeine decreased PPI levels at two doses in the high inhibitory group; however, 10 mg/kg dose caffeine was increased only in the low inhibitory group. According to the data obtained from this study, rats can be grouped with baseline inhibition values by using PPI, and response differences of pharmacological agents to groups may vary.

Effects of Permethrin or Deltamethrin Exposure in Adult Sprague Dawley Rats on Acoustic and Light Prepulse Inhibition of Acoustic or Tactile Startle.

The effects of permethrin (PRM) and deltamethrin (DLM) on acoustic or light prepulse inhibition of the acoustic startle response (ASR) and tactile startle response (TSR) were studied in adult male Sprague Dawley rats. Preliminary studies were conducted to optimize the parameters of light and acoustic prepulse inhibition of ASR and TSR. Once these parameters were set, a new group of rats was administered PRM (0 or 90 mg/kg) or DLM (0 or 25 mg/kg) by gavage in 5 mL/kg corn oil. ASR and TSR were assessed using acoustic or light prepulses 6, 8, and 12 h after PRM and 2, 4, and 6 h after DLM exposure. PRM increased ASR 6 h post-treatment with no interaction with acoustic prepulse levels and with no effect on TSR. When light was used as the prepulse, PRM increased ASR and TSR at 6 h with no interaction with prepulse levels. DLM decreased ASR and TSR on trials without prepulses but not on trials with acoustic prepulses. DLM also decreased ASR when light prepulses were present 4 h post-treatment. A final experiment assessed whether the house light in the test cabinet affected ASR and TSR after PRM or DLM exposure. Rats had increased ASR and TSR when house lights were on compared with when they were off, but lighting did not differentially interact with PRM or DLM. Light and acoustic prepulses of ASR and TSR have different effects depending on the test agent and the test parameters.

LL-00066471, a novel positive allosteric modulator of α7 nicotinic acetylcholine receptor ameliorates cognitive and sensorimotor gating deficits in animal models: Discovery and preclinical characterization.

α7 nicotinic acetylcholine receptor (α7 nAChR) is an extensively validated target for several neurological and psychiatric conditions namely, dementia and schizophrenia, owing to its vital roles in cognition and sensorimotor gating. Positive allosteric modulation (PAM) of α7 nAChR represents an innovative approach to amplify endogenous cholinergic signaling in a temporally restricted manner in learning and memory centers of brain. α7 nAChR PAMs are anticipated to side-step burgeoning issues observed with several clinical-stage orthosteric α7 nAChR agonists, related to selectivity, tolerance/tachyphylaxis, thus providing a novel dimension in therapeutic strategy and pharmacology of α7 nAChR ion-channel. Here we describe a novel α7 nAChR PAM, LL-00066471, which potently amplified agonist-induced Ca2+ fluxes in neuronal IMR-32 neuroblastoma cells in a α-bungarotoxin (α-BTX) sensitive manner. LL-00066471 showed excellent oral bioavailability across species (mouse, rat and dog), low clearance and good brain penetration (B/P ratio > 1). In vivo, LL-00066471 robustly attenuated cognitive deficits in both procognitive and antiamnesic paradigms of short-term episodic and recognition memory in novel object recognition task (NORT) and social recognition task (SRT), respectively. Additionally, LL-00066471 mitigated apomorphine-induced sensorimotor gating deficits in acoustic startle reflex (ASR) and enhanced antipsychotic efficacy of olanzapine in conditioned avoidance response (CAR) task. Further, LL-00066471 corrected redox-imbalances and reduced cortico-striatal infarcts in stroke model. These finding together suggest that LL-00066471 has potential to symptomatically alleviate cognitive deficits associated with dementias, attenuate sensorimotor gating deficits in schizophrenia and correct redox-imbalances in cerebrovascular disorders. Therefore, LL-00066471 presents potential for management of cognitive impairments associated with neurological and psychiatric conditions.

A Methyltransferase Inhibitor (Decitabine) Alleviates Intergenerational Effects of Paternal Neonatal Exposure to Anesthesia With Sevoflurane.

BACKGROUND: Neonatal exposure to sevoflurane induces neurobehavioral and neuroendocrine abnormalities in exposed male rats (generation F0) and neurobehavioral, but not neuroendocrine, abnormalities in their male, but not female, offspring (generation F1). These effects of sevoflurane are accompanied by a hypermethylated neuron-specific K-2Cl (Kcc2) Cl exporter gene in the F0 spermatozoa and the F1 male hypothalamus, while the gene's expression is reduced in the F0 and F1 hypothalamus. We investigated whether inhibition of deoxyribonucleic acid methyltransferases (DNMTs) before paternal sevoflurane exposure could alleviate the anesthetic's F0 and F1 effects. METHODS: Sprague-Dawley male rats were anesthetized with 2.1% sevoflurane for 5 hours on postnatal day (P) 5 and mated with control females on P90 to generate offspring. The nonselective DNMT inhibitor decitabine (0.5 mg/kg, intraperitoneally) was administered 30 minutes before sevoflurane exposure. The F0 and F1 male rats were evaluated in in vivo and in vitro tests in adulthood. RESULTS: Paternal exposure to sevoflurane induced impaired prepulse inhibition of the acoustic startle response and exacerbated corticosterone responses to stress in F0 males and impaired prepulse inhibition of the startle responses in F1 males. These effects were accompanied in both generations by reduced and increased expressions of hypothalamic Kcc2 and Dnmt3a/b, respectively. Decitabine deterred the effects of paternal exposure to sevoflurane in F0 and F1 males. CONCLUSIONS: These results suggest that similar decitabine-sensitive mechanisms regulating expression of multiple genes are involved in the mediation of neurobehavioral abnormalities in sires neonatally exposed to sevoflurane and in their future unexposed male offspring.

Maternal Immune Activation Sensitizes Male Offspring Rats to Lipopolysaccharide-Induced Microglial Deficits Involving the Dysfunction of CD200-CD200R and CX3CL1-CX3CR1 Systems.

Early life challenges resulting from maternal immune activation (MIA) may exert persistent effects on the offspring, including the development of psychiatric disorders, such as schizophrenia. Recent evidence has suggested that the adverse effects of MIA may be mediated by neuron-microglia crosstalk, particularly CX3CL1-CX3CR1 and CD200-CD200R dyads. Therefore, the present study assessed the behavioural parameters resembling schizophrenia-like symptoms in the adult male offspring of Sprague-Dawley rats that were exposed to MIA and to an additional acute lipopolysaccharide (LPS) challenge in adulthood, according to the "two-hit" hypothesis of schizophrenia. Simultaneously, we aimed to clarify the role of the CX3CL1-CX3CR1 and CD200-CD200R axes and microglial reactivity in the brains of adult offspring subjected to MIA and the "second hit" wit LPS. In the present study, MIA generated a range of behavioural changes in the adult male offspring, including increased exploratory activity and anxiety-like behaviours. The most intriguing finding was observed in the prepulse inhibition (PPI) test, where the deficit in the sensorimotor gating was age-dependent and present only in part of the rats. We were able to distinguish the occurrence of two groups: responsive and non-responsive (without the deficit). Concurrently, based on the results of the biochemical studies, MIA disrupted mainly the CD200-CD200R system, while the changes of the CX3CL1-CX3CR1 axis were less evident in the frontal cortex of adult non-responsive offspring. MIA markedly affected the immune regulators of the CD200-CD200R pathway as we observed an increase in cortical IL-6 release in the responsive group and IL-4 in the non-responsive offspring. Importantly, the "second hit" generated disturbances at the behavioural and biochemical levels mostly in the non-responsive adult animals. Those offspring were characterized both by disturbed PPI and "priming" microglia. Altogether, the exposure to MIA altered the immunomodulatory mechanisms, including the CD200-CD200R axis, in the brain and sensitized animals to subsequent immunological challenges, leading to the manifestation of schizophrenia-like alterations.

NMDAR Antibodies Alter Dopamine Receptors and Cause Psychotic Behavior in Mice.

OBJECTIVE: The aim was to demonstrate that antibodies from patients with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis alter the levels of dopamine 1 receptor (D1R) and dopamine 2 receptor (D2R) and cause psychotic-like features in mice. METHODS: Cultured rat hippocampal neurons were treated with cerebrospinal fluid (CSF) from patients with anti-NMDAR encephalitis or controls, and the effects on clusters of D1R and D2R were quantified. In vivo studies included 71 C57BL/6J mice that were chronically infused with CSF from patients or controls through ventricular catheters connected to subcutaneous osmotic pumps. Prepulse inhibition of the acoustic startling reflex (PPI; a marker of psychotic-like behavior), memory, locomotor activity, and the density of cell-surface and synaptic D1R, D2R, and NMDAR clusters were examined at different time points using reported techniques. RESULTS: In cultured neurons, CSF from patients, but not from controls, caused a significant decrease of cell-surface D1R and an increase of D2R clusters. In mice, CSF from patients caused a significant decrease of synaptic and total cell-surface D1R clusters and an increase of D2R clusters associated with a decrease of PPI. These effects were accompanied by memory impairment and a reduction of surface NMDARs, as reported in this model. The psychotic-like features, memory impairment, and changes in levels of D1R, D2R, and NMDAR progressively improved several days after the infusion of CSF from patients stopped. INTERPRETATION: In addition to memory deficits and reduction of NMDARs, CSF antibodies from patients with anti-NMDAR encephalitis cause reversible psychotic-like features accompanied by changes (D1R decrease, D2R increase) in cell-surface dopamine receptor clusters. ANN NEUROL 2020 ANN NEUROL 2020;88:603-613.

Differential Effects of Nicotine and Nicotine Withdrawal on Fear Conditioning in Male Rats.

BACKGROUND: Tobacco use is prevalent in individuals who are routinely exposed to stress. However, little is known about how nicotine affects responses to trauma. We examined in rats how nicotine exposure affects fear conditioning, a procedure often used to study stress-related psychiatric illness. METHODS: We examined 2 methods of nicotine exposure: self-administration, modeling voluntary use, and experimenter-programmed subcutaneous administration, modeling medicinal administration (nicotine patch). For self-administered nicotine, rats trained to self-administer nicotine i.v. were fear conditioned (via light cue preceding foot-shock) either immediately after a 12-hour self-administration session or 12 hours later during a period with somatic signs of nicotine withdrawal. For experimenter-delivered nicotine, rats were conditioned after 1-21 days of nicotine delivered by programmable (12 hours on) subcutaneous mini-pumps. Tests to evaluate acoustic startle responses to the conditioning environment (context-potentiated startle) and in the presence or absence of the light cue (fear-potentiated startle) occurred after a 10-day period. RESULTS: Rats fear conditioned immediately after nicotine self-administration showed reduced responses to the shock-associated context, whereas those trained during nicotine withdrawal showed exaggerated responses. Experimenter-programmed nicotine produced effects qualitatively similar to those seen with self-administered nicotine. CONCLUSIONS: Self-administration or experimenter-programmed delivery of nicotine immediately before exposure to aversive events can reduce conditioned fear responses. In contrast, exposure to aversive events during nicotine withdrawal exacerbates fear responses. These studies raise the possibility of developing safe and effective methods to deliver nicotine or related drugs to mitigate the effects of stress while also highlighting the importance of preventing withdrawal in nicotine-dependent individuals.

A botanical drug composed of three herbal materials attenuates the sensorimotor gating deficit and cognitive impairment induced by MK-801 in mice.

OBJECTIVES: A botanical drug derived from the ethanolic extract composed of Clematis chinensis Osbeck (Ranunculaceae), Trichosanthes kirilowii Maximowicz (Cucurbitaceae) and Prunella vulgaris Linné (Lamiaceae) has been used to ameliorate rheumatoid arthritis as an ethical drug in Korea. In our study, we investigated the effect of this herbal complex extract (HCE) on schizophrenia-like behaviours induced by MK-801. METHODS: HCE (30, 100 or 300 mg/kg, p.o) was orally administered to male ICR mice to a schizophrenia-like animal model induced by MK-801. We conducted an acoustic startle response task, an open-field task, a novel object recognition task and a social novelty preference task. KEY FINDINGS: We found that a single administration of HCE (100 or 300 mg/kg) ameliorated MK-801-induced abnormal behaviours including sensorimotor gating deficits and social or object recognition memory deficits. In addition, MK-801-induced increases in phosphorylated Akt and GSK-3ß expression levels in the prefrontal cortex were reversed by HCE (30, 100 or 300 mg/kg). CONCLUSIONS: These results imply that HCE ameliorates MK-801-induced dysfunctions in prepulse inhibition, social interactions and cognitive function, partly by regulating the Akt and GSK-3ß signalling pathways.

Role of the PACAP system of the extended amygdala in the acoustic startle response in rats.

Anxiety-related disorders are the most prevalent mental disorders in the world and they are characterized by abnormal responses to stressors. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide highly expressed in the extended amygdala, a brain macrostructure involved in the response to threat that includes the central nucleus of the amygdala (CeA) and the bed nucleus of the stria terminalis (BNST). The aim of this series of experiments was to systematically elucidate the role of the PACAP system of the CeA and BNST under both control, unstressed conditions and after the presentation of a stressor in rats. For this purpose, we used the acoustic startle response (ASR), an unconscious response to sudden acoustic stimuli sensitive to changes in stress which can be used as an operationalization of the hypervigilance present in anxiety- and trauma-related disorders. We found that infusion of PACAP, but not the related peptide vasoactive intestinal peptide (VIP), into either the CeA or the BNST causes a dose-dependent increase in ASR. In addition, while infusion of the antagonist PACAP(6-38) into either the CeA or the BNST does not affect ASR in non-stressed conditions, it prevents the sensitization of ASR induced by an acute footshock stress. Finally, we found that footshock stress induces a significant increase in PACAP, but not VIP, levels in both of these brain areas. Altogether, these data show that the PACAP system of the extended amygdala contributes to stress-induced hyperarousal and suggest it as a potential novel target for the treatment of stress-related disorders.

Histamine H3 receptor activation reduces the impairment in prepulse inhibition (PPI) of the acoustic startle response and Akt phosphorylation induced by MK-801 (dizocilpine), antagonist at N-Methyl-d-Aspartate (NMDA) receptors.

We have investigated the effect of the local activation of histamine H3 receptors (H3Rs) in the rat prefrontal cortex (PFCx) on the impairment of pre-pulse inhibition (PPI) of the startle response induced by the systemic administration of MK-801, antagonist at glutamate N-Methyl-d-Aspartate (NMDA) receptors, and the possible functional interaction between H3Rs and MK-801 on PFCx dopaminergic transmission. Infusion of the H3R agonist RAMH (19.8 ng/1 µl) into the PFCx reduced or prevented the inhibition by MK-801 (0.15 mg/kg, ip) of PPI evoked by different auditory stimulus intensities (5, 10 and 15 dB), and the RAMH effect was blocked by the H3R antagonist/inverse agonist ciproxifan (30.6 ng/1 µl). MK-801 inhibited [3H]-dopamine uptake (-45.4 ±â€¯2.1%) and release (-32.8 ±â€¯2.6%) in PFCx synaptosomes or slices, respectively, and molecular modeling indicated that MK-801 binds to and blocks the rat and human dopamine transporters. However, H3R activation had no effect on the inhibitory action of MK-801 on dopamine uptake and release. In PFCx slices, MK-801 and the activation of H3Rs or dopamine D1 receptors (D1Rs) stimulated ERK-1/2 and Akt phosphorylation. The co-activation of D1Rs and H3Rs prevented ERK-1/2 and Akt phosphorylation, and H3R activation or D1R blockade prevented the effect of MK-801. In ex vivo experiments, the intracortical infusion of the D1R agonist SKF-81297 (37 ng/1 µl) or the H3R agonist RAMH increased Akt phosphorylation, prevented by D1R/H3R co-activation. These results indicate that MK-801 enhances dopaminergic transmission in the PFCx, and that H3R activation counteracts the post-synaptic actions of dopamine.

Metformin reverses the schizophrenia-like behaviors induced by MK-801 in rats.

Schizophrenia is known to be a complex and disabling psychiatric disorder. Dopamine receptor antagonists have a significant therapeutic effect in improving the positive symptoms that are associated with the illness. Therefore, dopamine receptor antagonists are commonly used in the treatment of schizophrenia; however, they do not achieve satisfactory results in improving negative symptoms and cognitive impairment. Metformin, widely known as an antidiabetic drug, has been found to enhance spatial memory formation and improve anxiety-like behaviors in rodents. Metformin's neuroprotective effect has been well documented in several neurological disorders including Alzheimer's disease, Parkinson's disease, strokes, Huntington's disease, and seizures. In the present study, we used a rat model to explore the effect of metformin on schizophrenia-like behaviors induced by MK-801 (dizocilpine), an N-methyl-D-aspartate (NMDA) receptor antagonist. We found that the pre-pulse inhibition (PPI) deficit caused by MK-801 could be alleviated by metformin. The hyperlocomotion in the open field test induced by chronic treatment of MK-801 was reversed by administration of metformin. Metformin has no effect on the baseline level of anxiety in normal naive rats, while metformin could relieve the anxiety-like behaviors in MK-801-treatment rats, though this effect is not reaching a significant level. Additionally, metformin could significantly ameliorate working memory impairments induced by MK-801. Moreover, the increased level of phosphorylation of Akt and GSK3ß in the frontal cortex induced by MK-801 was normalized by metformin. In conclusion, our results demonstrate that metformin improved schizophrenia-like symptoms in rats, and is therefore a potential agent for the treatment of schizophrenia.

Chronic Suppression of Glucagon-Like Peptide-1 Receptor (GLP1R) mRNA Translation in the Rat Bed Nucleus of the Stria Terminalis Reduces Anxiety-Like Behavior and Stress-Induced Hypophagia, But Prolongs Stress-Induced Elevation of Plasma Corticosterone.

The anterior lateral bed nucleus of the stria terminalis (alBST) expresses glucagon-like peptide-1 receptors (GLP1Rs) and receives input from caudal brainstem GLP1 neurons. GLP1 administered centrally reduces food intake and increases anxiety-like behavior and plasma corticosterone (cort) levels in rats, whereas central GLP1R antagonism has opposite effects. Anxiogenic threats and other stressors robustly activate c-fos expression in both GLP1-producing neurons and also in neurons within alBST subregions expressing GLP1R. To examine the functional role of GLP1R signaling within the alBST, adult male Sprague Dawley rats received bilateral alBST-targeted injections of an adeno-associated virus (AAV) vector expressing short hairpin RNA (shRNA) to knock down the translation of GLP1R mRNA (GLP1R-KD rats), or similar injections of a control AAV (CTRL rats). In situ hybridization revealed that GLP1R mRNA is expressed in a subset of GABAergic alBST neurons, and quantitative real-time PCR confirmed that GLP1R-KD rats displayed a significant 60% reduction in translatable GLP1R mRNA. Compared with CTRL rats, GLP1R-KD rats gained more body weight over time and displayed less anxiety-like behavior, including a loss of light-enhanced acoustic startle and less stress-induced hypophagia. Conversely, while baseline plasma cort levels were similar in GLP1R-KD and CTRL rats, GLP1R-KD rats displayed a prolonged stress-induced elevation of plasma cort levels. GLP1R-KD and CTRL rats displayed similar home cage food intake and a similar hypophagic response to systemic Exendin-4, a GLP1R agonist that crosses the blood-brain barrier. We conclude that GLP1R expressed within the alBST contributes to multiple behavioral responses to anxiogenic threats, yet also serves to limit the plasma cort response to acute stress.SIGNIFICANCE STATEMENT Anxiety is an affective and physiological state that supports threat avoidance. Identifying the neural bases of anxiety-like behaviors in animal models is essential for understanding mechanisms that contribute to normative and pathological anxiety in humans. In rats, anxiety/avoidance behaviors can be elicited or enhanced by visceral or cognitive threats that increase glucagon-like peptide-1 (GLP1) signaling from the caudal brainstem to the hypothalamus and limbic forebrain. Data reported here support a role for limbic GLP1 receptor signaling to enhance anxiety-like behavior and to attenuate stress-induced elevations in plasma cort levels in rats. Improved understanding of central GLP1 neural pathways that impact emotional responses to stress could expand potential therapeutic options for anxiety and other stress-related disorders in humans.

Chronic cannabis promotes pro-hallucinogenic signaling of 5-HT2A receptors through Akt/mTOR pathway.

Long-term use of potent cannabis during adolescence increases the risk of developing schizophrenia later in life, but to date, the mechanisms involved remain unknown. Several findings suggest that the functional selectivity of serotonin 2A receptor (5-HT2AR) through inhibitory G-proteins is involved in the molecular mechanisms responsible for psychotic symptoms. Moreover, this receptor is dysregulated in the frontal cortex of schizophrenia patients. In this context, studies involving cannabis exposure and 5-HT2AR are scarce. Here, we tested in mice the effect of an early chronic Δ9-tetrahydrocannabinol (THC) exposure on cortical 5-HT2AR expression, as well as on its in vivo and in vitro functionality. Long-term exposure to THC induced a pro-hallucinogenic molecular conformation of the 5-HT2AR and exacerbated schizophrenia-like responses, such as prepulse inhibition disruption. Supersensitive coupling of 5-HT2AR toward inhibitory Gαi1-, Gαi3-, Gαo-, and Gαz-proteins after chronic THC exposure was observed, without changes in the canonical Gαq/11-protein pathway. In addition, we found that inhibition of Akt/mTOR pathway by rapamycin blocks the changes in 5-HT2AR signaling pattern and the supersensitivity to schizophrenia-like effects induced by chronic THC. The present study provides the first evidence of a mechanistic explanation for the relationship between chronic cannabis exposure in early life and increased risk of developing psychosis-like behaviors in adulthood.

Direct and indirect nigrofugal projections to the nucleus reticularis pontis caudalis mediate in the motor execution of the acoustic startle reflex.

The acoustic startle reflex (ASR) is a short and intense defensive reaction in response to a loud and unexpected acoustic stimulus. In the rat, a primary startle pathway encompasses three serially connected central structures: the cochlear root neurons, the giant neurons of the nucleus reticularis pontis caudalis (PnC), and the spinal motoneurons. As a sensorimotor interface, the PnC has a central role in the ASR circuitry, especially the integration of different sensory stimuli and brain states into initiation of motor responses. Since the basal ganglia circuits control movement and action selection, we hypothesize that their output via the substantia nigra (SN) may interplay with the ASR primary circuit by providing inputs to PnC. Moreover, the pedunculopontine tegmental nucleus (PPTg) has been proposed as a functional and neural extension of the SN, so it is another goal of this study to describe possible anatomical connections from the PPTg to PnC. Here, we made 6-OHDA neurotoxic lesions of the SN pars compacta (SNc) and submitted the rats to a custom-built ASR measurement session to assess amplitude and latency of motor responses. We found that following lesion of the SNc, ASR amplitude decreased and latency increased compared to those values from the sham-surgery and control groups. The number of dopamine neurons remaining in the SNc after lesion was also estimated using a stereological approach, and it correlated with our behavioral results. Moreover, we employed neural tract-tracing techniques to highlight direct projections from the SN to PnC, and indirect projections through the PPTg. Finally, we also measured levels of excitatory amino acid neurotransmitters in the PnC following lesion of the SN, and found that they change following an ipsi/contralateral pattern. Taken together, our results identify nigrofugal efferents onto the primary ASR circuit that may modulate motor responses.

Characterization of Behavioral, Signaling and Cytokine Alterations in a Rat Neurodevelopmental Model for Schizophrenia, and Their Reversal by the 5-HT6 Receptor Antagonist SB-399885.

Post-weaning social isolation of rats produces neuroanatomical, neurochemical and behavioral alterations resembling some core features of schizophrenia. This study examined the ability of the 5-HT6 receptor antagonist SB-399885 to reverse isolation-induced cognitive deficits, then investigated alterations in hippocampal cell proliferation and hippocampal and frontal cortical expression of selected intracellular signaling molecules and cytokines. Male Lister hooded rats (weaned on post-natal days 21-24 and housed individually or in groups of 3-4) received six i.p. injections of vehicle (1% Tween 80, 1 mL/kg) or SB-399885 (5 or 10 mg/kg) over a 2-week period starting 40 days post-weaning, on the days that locomotor activity, novel object discrimination (NOD), pre-pulse inhibition of acoustic startle and acquisition, retention and extinction of a conditioned freezing response (CFR) were assessed. Tissue was collected 24 h after the final injection for immunohistochemistry, reverse-phase protein microarray and western blotting. Isolation rearing impaired NOD and cue-mediated CFR, decreased cell proliferation within the dentate gyrus, and elevated hippocampal TNFα levels and Cdc42 expression. SB-399885 reversed the NOD deficit and partially normalized CFR and cell proliferation. These effects were accompanied by altered expression of several members of the c-Jun N-terminal Kinase (JNK) and p38 MAPK signaling pathways (including TAK1, MKK4 and STAT3). Although JNK and p38 themselves were unaltered at this time point hippocampal TAK1 expression and phosphorylation correlated with visual recognition memory in the NOD task. Continued use of this neurodevelopmental model could further elucidate the neurobiology of schizophrenia and aid assessment of novel therapies for drug-resistant cognitive symptoms.

Bumetanide blocks the acquisition of conditioned fear in adult rats.

BACKGROUND AND PURPOSE: Bumetanide has anxiolytic effects in rat models of conditioned fear. As a loop diuretic, bumetanide blocks cation-chloride co-transport and this property may allow bumetanide to act as an anxiolytic by modulating GABAergic synaptic transmission in the CNS. Its potential for the treatment of anxiety disorders deserves further investigation. In this study, we evaluated the possible involvement of the basolateral nucleus of the amygdala in the anxiolytic effect of bumetanide. EXPERIMENTAL APPROACH: Brain slices were prepared from Wistar rats. extracellular recording, stereotaxic surgery, fear-potentiated startle response, locomotor activity monitoring and Western blotting were applied in this study. KEY RESULTS: Systemic administration of bumetanide (15.2 mg·kg-1 , i.v.), 30 min prior to fear conditioning, significantly inhibited the acquisition of the fear-potentiated startle response. Phosphorylation of ERK in the basolateral nucleus of amygdala was reduced after bumetanide administration. In addition, suprafusion of bumetanide (5 or 10 µM) attenuated long-term potentiation in the amygdala in a dose-dependent manner. Intra-amygdala infusion of bumetanide, 15 min prior to fear conditioning, also blocked the acquisition of the fear-potentiated startle response. Finally, the possible off-target effect of bumetanide on conditioned fear was excluded by side-by-side control experiments. CONCLUSIONS AND IMPLICATIONS: These results suggest the basolateral nucleus of amygdala plays a critical role in the anxiolytic effects of bumetanide.

The Sigma-1 Receptor Antagonist, S1RA, Reduces Stroke Damage, Ameliorates Post-Stroke Neurological Deficits and Suppresses the Overexpression of MMP-9.

The glutamate N-methyl-D-aspartate receptor (NMDAR) plays an essential role in the excitotoxic neural damage that follows ischaemic stroke. Because the sigma-1 receptor (σ1R) can regulate NMDAR transmission, exogenous and putative endogenous regulators of σ1R have been investigated using animal models of ischaemic stroke. As both agonists and antagonists provide some neural protection, the selective involvement of σ1Rs in these effects has been questioned. The availability of S1RA (E-52862/MR309), a highly selective σ1R antagonist, prompted us to explore its therapeutic potential in an animal model of focal cerebral ischaemia. Mice were subjected to right middle cerebral artery occlusion (MCAO), and post-ischaemic infarct volume and neurological deficits were determined across a range of intervals after the stroke-inducing surgery. Intracerebroventricular or intravenous treatment with S1RA significantly reduced the cerebral infarct size and neurological deficits caused by permanent MCAO (pMCAO). Compared with the control/sham-operated mice, the neuroprotective effects of S1RA were observed when delivered up to 5 h prior to surgery and 3 h after ischaemic onset. Interestingly, neither mice with the genetic deletion of σ1R nor wild-type mice that were pre-treated with the σ1R agonist PRE084 showed beneficial effects after S1RA administration with regard to stroke infarction. S1RA-treated mice showed faster behavioural recovery from stroke; this finding complements the significant decreases in matrix metalloproteinase-9 (MMP-9) expression and reactive astrogliosis surrounding the infarcted cortex. Our data indicate that S1RA, via σ1R, holds promising potential for clinical application as a therapeutic agent for ischaemic stroke.

N-acetyl cysteine reverses bio-behavioural changes induced by prenatal inflammation, adolescent methamphetamine exposure and combined challenges.

RATIONALE: Schizophrenia is associated with prenatal inflammation and/or postnatal stressors such as drug abuse, resulting in immune-redox dysfunction. Antioxidants may offer therapeutic benefits. OBJECTIVES: The objective of this study is to investigate N-acetyl cysteine (NAC) as a therapeutic antioxidant to reverse schizophrenia-like bio-behavioural changes in rats exposed to maternal immune activation (MIA), adolescent methamphetamine (MA) or a combination thereof. METHODS: Sprague-Dawley offspring prenatally exposed to saline/lipopolysaccharide (LPS) received saline or MA (0.2-6 mg kg-1 twice daily × 16 days) during adolescence and divided into LPS, MA and LPS + MA groups. Vehicle/NAC (150 mg kg-1 × 14 days) was administered following MA/saline exposure on postnatal day 51-64. Social interaction, novel object recognition and prepulse inhibition (PPI) of startle, as well as regional brain monoamines, lipid peroxidation, plasma reactive oxygen species (ROS) and pro- and anti-inflammatory cytokines (TNF-α; IL-10), were assessed. RESULTS: NAC reversed LPS, MA and LPS + MA-induced anxiety-like social withdrawal behaviours, as well as MA and LPS + MA-induced deficits in recognition memory. PPI deficits were evident in MA, LPS and LPS + MA models, with NAC reversing that following LPS + MA. NAC reversed LPS, MA and LPS + MA-induced frontal cortical dopamine (DA) and noradrenaline (NA) elevations, LPS and LPS + MA-induced frontal cortical 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and striatal NA deficits as well as LPS + MA-induced frontal cortical 5-HT turnover. Decreased IL-10 in the LPS, MA and LPS + MA animals, and increased TNF-α in the LPS and MA animals, was reversed with NAC. NAC also reversed elevated lipid peroxidation and ROS in the LPS and LPS + MA animals. CONCLUSIONS: Prenatal LPS, LPS + postnatal MA challenge during adolescence, and to a lesser extent MA alone, promotes schizophrenia-like bio-behavioural changes later in life that are reversed by NAC, emphasizing therapeutic potential for schizophrenia and MA-associated psychosis. The nature and timing of the dual-hit are critical.

The Differential Binding of Antipsychotic Drugs to the ABC Transporter P-Glycoprotein Predicts Cannabinoid-Antipsychotic Drug Interactions.

Cannabis use increases rates of psychotic relapse and treatment failure in schizophrenia patients. Clinical studies suggest that cannabis use reduces the efficacy of antipsychotic drugs, but there has been no direct demonstration of this in a controlled study. The present study demonstrates that exposure to the principal phytocannabinoid, Δ9-tetrahydrocannabinol (THC), reverses the neurobehavioral effects of the antipsychotic drug risperidone in mice. THC exposure did not influence D2 and 5-HT2A receptor binding, the major targets of antipsychotic action, but it lowered the brain concentrations of risperidone and its active metabolite, 9-hydroxy risperidone. As risperidone and its active metabolite are excellent substrates of the ABC transporter P-glycoprotein (P-gp), we hypothesized that THC might increase P-gp expression at the blood-brain barrier (BBB) and thus enhance efflux of risperidone and its metabolite from brain tissue. We confirmed that the brain disposition of risperidone and 9-hydroxy risperidone is strongly influenced by P-gp, as P-gp knockout mice displayed greater brain concentrations of these drugs than wild-type mice. Furthermore, we demonstrated that THC exposure increased P-gp expression in various brain regions important to risperidone's antipsychotic action. We then showed that THC exposure did not influence the neurobehavioral effects of clozapine. Clozapine shares a very similar antipsychotic mode of action to risperidone, but unlike risperidone is not a P-gp substrate. Our results imply that clozapine or non-P-gp substrate antipsychotic drugs may be better first-line treatments for schizophrenia patients with a history of cannabis use.