Effect of GABAB receptor antagonist (CGP35348) on learning and memory in albino mice

Stochastic characterization of navigation strategies in an automated variant of the Barnes maze

Animals can use a repertoire of strategies to navigate in an environment, and it remains an intriguing question how these strategies are selected based on the nature and familiarity of environments. To investigate this question, we developed a fully automated variant of the Barnes maze, characterized by 24 vestibules distributed along the periphery of a circular arena, and monitored the trajectories of mice over 15 days as they learned to navigate towards a goal vestibule from a random start vestibule. We show that the patterns of vestibule visits can be reproduced by the combination of three stochastic processes reminiscent of random, serial, and spatial strategies. The processes randomly selected vestibules based on either uniform (random) or biased (serial and spatial) probability distributions. They closely matched experimental data across a range of statistical distributions characterizing the length, distribution, step size, direction, and stereotypy of vestibule sequences, revealing a shift from random to spatial and serial strategies over time, with a strategy switch occurring approximately every six vestibule visits. Our study provides a novel apparatus and analysis toolset for tracking the repertoire of navigation strategies and demonstrates that a set of stochastic processes can largely account for exploration patterns in the Barnes maze.

Modulation of GABAB receptors in the insula bidirectionally affects associative memory of epilectic rats in both spatial and non-spatial operant tasks

Background

Stimulation of gamma-aminobutyric acid (GABA) activity through GABA receptor agonists is the basic mechanism of many anticonvulsant drugs. Nevertheless, many of these GABergic drugs have adverse cognitive effects. We previously found that GABAB receptors (GABA_BRs) in the insula regulate operant associative memory in healthy rats. The present study aimed at investigating the effects of GABA_BR modulation in the insula on operant associative memory in epileptic rats, along with the underlying mechanisms.

Methods

The lithium-pilocarpine model of temporal lobe epilepsy (TLE) was established in male Sprague-Dawley rats. A 22-gauge stainless-steel guide cannula was surgically implanted into the granular insula cortex of the epileptic rats. Baclofen (125 ng/μl, 1 μl), CGP35348 (12.5 μg/μl, 1 μl), or saline (1 μl) was slowly infused through the guide cannula. The Intellicage automated behavioral testing system was used to evaluate operant associative memory of the epileptic rats, including non-spatial operant tasks (basic nosepoke learning and skilled nosepoke learning) and spatial operant tasks (chamber position learning). The expression of the GABA_BR subunits GB1 and GB2 in the insula was examined by immunofluorescence and Western blotting.

Results

The Intellicage tests demonstrated that baclofen significantly impaired basic nosepoke learning, skilled nosepoke learning and chamber position learning of the epileptic rats, while CGP35348 boosted these functions. Immunofluorescence staining revealed that GB1 and GB2 were expressed in the insula of the epileptic rats, and Western blotting analysis showed that baclofen enhanced while CGP35348 inhibited the expression of these subunits.

Conclusion

GABA_BRs in the insula bidirectionally regulate both spatial and non-spatial operant associative memory of epileptic rats. Effects of GABA_BRs on cognition should be taken into account when evaluating new possible treatments for people with epilepsy.

Synaptic Secretion and Beyond: Targeting Synapse and Neurotransmitters to Treat Neurodegenerative Diseases

The nervous system is important, because it regulates the physiological function of the body. Neurons are the most basic structural and functional unit of the nervous system. The synapse is an asymmetric structure that is important for neuronal function. The chemical transmission mode of the synapse is realized through neurotransmitters and electrical processes. Based on vesicle transport, the abnormal information transmission process in the synapse can lead to a series of neurorelated diseases. Numerous proteins and complexes that regulate the process of vesicle transport, such as SNARE proteins, Munc18-1, and Synaptotagmin-1, have been identified. Their regulation of synaptic vesicle secretion is complicated and delicate, and their defects can lead to a series of neurodegenerative diseases. This review will discuss the structure and functions of vesicle-based synapses and their roles in neurons. Furthermore, we will analyze neurotransmitter and synaptic functions in neurodegenerative diseases and discuss the potential of using related drugs in their treatment.

GABAergic inhibitory neurons as therapeutic targets for cognitive impairment in schizophrenia

Schizophrenia is considered primarily as a cognitive disorder. However, functional outcomes in schizophrenia are limited by the lack of effective pharmacological and psychosocial interventions for cognitive impairment. GABA (gamma-aminobutyric acid) interneurons are the main inhibitory neurons in the central nervous system (CNS), and they play a critical role in a variety of pathophysiological processes including modulation of cortical and hippocampal neural circuitry and activity, cognitive function-related neural oscillations (eg, gamma oscillations) and information integration and processing. Dysfunctional GABA interneuron activity can disrupt the excitatory/inhibitory (E/I) balance in the cortex, which could represent a core pathophysiological mechanism underlying cognitive dysfunction in schizophrenia. Recent research suggests that selective modulation of the GABAergic system is a promising intervention for the treatment of schizophrenia-associated cognitive defects. In this review, we summarized evidence from postmortem and animal studies for abnormal GABAergic neurotransmission in schizophrenia, and how altered GABA interneurons could disrupt neuronal oscillations. Next, we systemically reviewed a variety of up-to-date subtype-selective agonists, antagonists, positive and negative allosteric modulators (including dual allosteric modulators) for α5/α3/α2 GABA_A and GABA_B receptors, and summarized their pro-cognitive effects in animal behavioral tests and clinical trials. Finally, we also discuss various representative histone deacetylases (HDAC) inhibitors that target GABA system through epigenetic modulations, GABA prodrug and presynaptic GABA transporter inhibitors. This review provides important information on current potential GABA-associated therapies and future insights for development of more effective treatments.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Effects of GABAB receptors in the insula on recognition memory observed with intellicage

BACKGROUND

Insular function has gradually become a topic of intense study in cognitive research. Recognition memory is a commonly studied type of memory in memory research. GABA_BR has been shown to be closely related to memory formation. In the present study, we used intellicage, which is a new intelligent behavioural test system, and a bilateral drug microinjection technique to inject into the bilateral insula, to examine the relationship between GABA_BR and recognition memory.

METHODS

Male Sprague-Dawley rats were randomly divided into control, Sham, Nacl, baclofen and CGP35348 groups. Different testing procedures were employed using intellicage to detect changes in rat recognition memory. The expression of GABA_BR (GB1, GB2) in the insula of rats was determined by immunofluorescence and western blotting at the protein level. In addition, the expression of GABA_BR (GB₁, GB₂) was detected by RT-PCR at the mRNA level.

RESULTS

The results of the intellicage test showed that recognition memory was impaired in terms of position learning, punitive learning and punitive reversal learning by using baclofen and CGP35348. In position reversal learning, no significant differences were found in terms of cognitive memory ability between the control groups and the CGP and baclofen groups. Immunofluorescence data showed GABA_BR (GB1, GB2) expression in the insula, while data from RT-PCR and western blot analysis demonstrated that the relative expression of GB1 and GB2 was significantly increased in the baclofen group compared with the control groups. In the CGP35348 group, the expression of GB1 and GB2 was significantly decreased, but there was no significant difference in GB1 or GB2 expression in the control groups.

CONCLUSIONS

GABA_BR expression in the insula plays an important role in the formation of recognition memory in rats.

Opposing needling promotes behavior recovery and exerts neuroprotection via the cAMP/PKA/CREB signal transduction pathway in transient MCAO rats

The aim of the present study was to investigate whether the cyclic adenosine 3′,5′-monophosphate (cAMP)/protein kinase A(PKA)/cAMP-responsive element binding protein (CREB) signal transduction pathway triggered by γ-aminobutyric acid class B (GABA_B) receptor activation is involved in neuroprotection against ischemia and behavioral recovery induced by opposing needling (ON). A total of 80 rats were randomly divided into four groups: A sham operation group, an ischemia group, an ON group and an ON group effectively inhibited by the GABA_B receptor antagonist, CGP35384 (n=20/group). The behavior of the rats was assessed by their neurological deficit score, whereas the impairment of gait was examined using the CatWalk system. The volume of cerebral infarction was examined upon treatment with 2,3,5-triphenyltetrazolium chloride. The expression levels of CREB, GABA_B1 and GABA_B2 were examined by western blotting and reverse transcription-quantitative polymerase chain reaction, and the activity of adenylyl cyclase (AC), cAMP and PKA in the serum was detected using an enzyme-linked immunosorbent assay. In the present study, in comparison with other groups, the ON group exhibited a reduced score for the neurological deficit, the stride length and swing speed were improved, and the volume of infarction was reduced. However, these effects were reversed upon administration of CGP35384. Additionally, the expression levels of CREB, GABA_B1 and GABA_B2 were increased in the ON group. The levels of AC, cAMP and PKA in the serum were also increased in the ON group, whereas the addition of CGP35384 reversed these effects. The results of the present study demonstrated that ON markedly protected the brain against transient cerebral ischemic injury, and this effect was possibly mediated by the activation of the GABA_B/cAMP/PKA/CREB signal transduction pathway. These findings implied that ON may be a potential therapeutic method for treating stroke.

Creatine monohydrate supplementation for 10 weeks mediates neuroprotection and improves learning/memory following neonatal hypoxia ischemia encephalopathy in female albino mice

Currently there are no uniform standard treatments for newborn suffering from cerebral hypoxia-ischemia (HI) and to find new and effective strategies for treating the HI injury remains a key direction for future research. Present study was designed to demonstrate that optimal dose (1 or 3%) of creatine monohydrate (Cr) for the treatment of neonatal HI in female albino mice. On postnatal day 10, animals were subjected to left carotid artery ligation followed by 8% hypoxia for 25 minutes. Following weaning on postnatal day 20, mice were divided into three treatments on the basis of diet supplementation (Normal rodent diet, 1% and 3% creatine supplemented diet) for 10 week. A battery of neurological tests (Rota rod, open field and Morris water maze) was used to demonstrate effect of Cr supplementation on neurofunction and infarct size following HI. Open field test results indicated that Cr supplementation had significantly improved locomotory and exploratory behavior in subjects. It was observed that Cr treated mice showed better neuromuscular coordination (rota rod) and improved spatial memory (Morris Water Maze test). A significant affect of creatine supplementation in reducing infarct size was also observed. Post hoc analysis of post hoc multiple comparisons revealed that mice supplemented with 3% Cr for 10 weeks performed better during Morris water maze test while 1% Cr supplementation improved the exploratory behavior and gain in body weight than control group indicating that Cr supplementation has the potential to improve the neurofunction following neonatal brain damage. This article is part of a Special Issue entitled SI: Brain and Memory.

Long term creatine monohydrate supplementation, following neonatal hypoxic ischemic insult, improves neuromuscular coordination and spatial learning in male albino mouse

Creatine is known to rescue animals following brain damage. Present study was designed to demonstrate the effect of long term (15 week) supplementation of 2% creatine monohydrate (Cr), following neonatal hypoxic ischemic insult, on learning and memory formation in male albino mouse. Albino mice pups were subjected to right common carotid artery ligation followed by 8% hypoxia for 25 minutes. Following weaning, animals were separated and grouped on the basis of dietry supplementation for 15 weeks followed by a battery of neurological tests including Morris water maze, open field and rota rod. It was observed that HI mice fed on 2% Cr for 15 weeks performed better than their littermates mice on normal rodent diet during water maze (learning and memory) and rotating rod (neuro-muscular coordination and balance) test while the results of open field test remained unaffected. It was also observed that Cr treated animals had a reduced brain infarct volume than untreated but this difference did not reached statistical significance. We have also observed an overall increase in body weight in Cr treated mice during the study. Over all our results are indicating that long term Cr supplementation is beneficial for male albino following hypoxic ischemic insult.

CGP 35348, GABA B receptor antagonist, has a potential to improve neuromuscular coordination and spatial learning in albino mouse following neonatal brain damage

To study the effect of CGP 35348 on learning and memory in albino mice following hypoxia ischemia insult, 10 days old albino mice were subjected to right common carotid artery ligation followed by 8% hypoxia for 25 minutes. Following brain damage, mice were fed on normal rodent diet till they were 13 week old. At this time point, mice were divided into two groups. Group 1 received saline and group 2 intrapertoneally CGP 35348 (1 mg/mL solvent/Kg body weight) for 12 days. A battery of tests used to assess long term neurofunction (Morris water maze, Rota rod and open field) along with brain infarct measurement. Overall CGP 35348 has improved the motor function in male and female albino mice but effects were more pronounced in female albino mice. In open field, CGP 35348 treated female albino mice had demonstrated poor exploratory behavior. During Morris water maze test, gender specific effects were observed as CGP 35348 had improved spatial learning and memory and swimming speed in male albino mice but had no effect in female albino mice following hypoxia ischemia encephalopathy (HIE). We concluded that GABAB receptor antagonists CGP 35348 can be used to improve gender based spatial memory.