Effects of GABA antagonists on inhibitory avoidance

Pharmacological characterization of a novel putative nootropic beta-alanine derivative, MB-005, in adult zebrafish

BACKGROUND

Cognitive deficits represent an urgent biomedical problem, and are commonly reduced by nootropic drugs. Animal models, including both rodents and zebrafish, offer a valuable tool for studying cognitive phenotypes and screening novel nootropics. Beta-alanine and its derivatives have recently been proposed to exert nootropic activity.

AIMS

This study aimed to characterize putative nootropic profile of a novel β-alanine analogue, 1,3-diaminopropane (MB-005), in adult zebrafish.

METHODS

Nootropic profile of MB-005 was assessed in adult zebrafish in the novel tank and conditioned place aversion (CPA) tests acutely, and in cued-learning plus-maze (PMT) tests chronically.

RESULTS/OUTCOMES

MB-005 did not alter zebrafish anxiety-like behavior or monoamine neurochemistry acutely, improved short-term memory in the CPA test, but impaired cognitive performance in both CPA and PMT tests chronically.

CONCLUSIONS/INTERPRETATION

This study reveals high sensitivity of zebrafish cognitive phenotypes to MB-005, suggesting it as a potential novel cognitive enhancer acutely, but raises concerns over its cognitive (and, possibly, other) side-effects chronically.

Effects of Ketamine and Midazolam on Simultaneous EEG/fMRI Data During Working Memory Processes

Reliable measures of cognitive brain activity from functional neuroimaging techniques may provide early indications of efficacy in clinical trials. Functional magnetic resonance imaging and electroencephalography provide complementary spatiotemporal information and simultaneous recording of these two modalities can remove inter-session drug response and environment variability. We sought to assess the effects of ketamine and midazolam on simultaneous electrophysiological and hemodynamic recordings during working memory (WM) processes. Thirty participants were included in a placebo-controlled, three-way crossover design with ketamine and midazolam. Compared to placebo, ketamine administration attenuated theta power increases and alpha power decreases and midazolam attenuated low beta band decreases to increasing WM load. Additionally, ketamine caused larger blood-oxygen-dependent (BOLD) signal increases in the supplementary motor area and angular gyrus, and weaker deactivations of the default mode network (DMN), whereas no difference was found between midazolam and placebo. Ketamine administration caused positive temporal correlations between frontal-midline theta (fm-theta) power and the BOLD signal to disappear and attenuated negative correlations. However, the relationship between fm-theta and the BOLD signal from DMN areas was maintained in some participants during ketamine administration, as increasing theta strength was associated with stronger BOLD signal reductions in these areas. The presence of, and ability to manipulate, both positive and negative associations between the BOLD signal and fm-theta suggest the presence of multiple fm-theta components involved in WM processes, with ketamine administration disrupting one or more of these theta-linked WM strategies.

How do stupendous cannabinoids modulate memory processing via affecting neurotransmitter systems?

In the present study, we wanted to review the role of cannabinoids in learning and memory in animal models, with respect to their interaction effects with six principal neurotransmitters involved in learning and memory including dopamine, glutamate, GABA (γ-aminobutyric acid), serotonin, acetylcholine, and noradrenaline. Cannabinoids induce a wide-range of unpredictable effects on cognitive functions, while their mechanisms are not fully understood. Cannabinoids in different brain regions and in interaction with different neurotransmitters, show diverse responses. Previous findings have shown that cannabinoids agonists and antagonists induce various unpredictable effects such as similar effect, paradoxical effect, or dualistic effect. It should not be forgotten that brain neurotransmitter systems can also play unpredictable roles in mediating cognitive functions. Thus, we aimed to review and discuss the effect of cannabinoids in interaction with neurotransmitters on learning and memory. In addition, we mentioned to the type of interactions between cannabinoids and neurotransmitter systems. We suggested that investigating the type of interactions is a critical neuropharmacological issue that should be considered in future studies.

Quantitative-profiling of neurotransmitter abnormalities in the disease progression of experimental diabetic encephalopathy rat

Diabetic encephalopathy (DE) is one of the most prevalent chronic complications of diabetes mellitus (DM), with neither effective prevention nor proven therapeutic regimen. This study aims to uncover the potential dysregulation pattern of the neurotransmitters in a rat model of streptozotocin (STZ)-induced experimental DE. For that purpose, male Sprague–Dawley (SD) rats were treated with a single intraperitoneal injection of STZ. Cognitive performance was detected with the Morris water maze (MWM) test. Serum, cerebrospinal fluid (CSF), and brain tissues were collected to measure the levels of neurotransmitters. Compared with the control rats, the acetylcholine (ACh) levels in serum, CSF, hippocampus, and cortex were all significantly down-regulated as early as 6 weeks in the STZ treatment group. In contrast, the glutamate (Glu) levels were decreased in CSF and the hippocampus, but unaffected in the serum and cortex of STZ-treated rats. As for γ-aminobutyric acid (GABA), it was down-regulated in serum, but up-regulated in CSF, hippocampus, and the cortex in the STZ-treated group. The mRNA expressions of neurotransmitter-related rate limiting enzymes (including AChE, GAD1, and GAD2) and pro-inflammatory cytokines (including IL-1β and TNF-α) were all increased in the DE rats. Our data suggest that DM induces isoform-dependent and tissue-specific neurotransmitter abnormalities, and that neuroinflammation may underlay the nervous system dysfunction observed in the progression of DE.

Reversal of neurobehavioral and neurochemical alterations in STZ-induced diabetic rats by FeTMPyP, a peroxynitrite decomposition catalyst and 1,5-Isoquinolinediol a poly(ADP-ribose) polymerase inhibitor

OBJECTIVE

In this study, we have evaluated the involvement of nitrosative stress and poly-ADP ribosyl polymerase (PARP) in diabetes induced neurobehavioral and neurochemical changes using pharmacological agents peroxynitrite decomposition catalyst (FeTMPyP) and a PARP inhibitor (1,5-Isoquinolinediol) in diabetic brains.

METHODS

The extent of neurobehavioral changes was assessed by functional observation battery, motor coordination activity (rota rod performance) and passive avoidance test. Neurochemical changes were assessed by measuring nicotinamide adenine dinucleotide (NAD), malondialdehyde, acetylcholinesterase, neurotransmitters (GABA and glutamate) levels in the hippocampus. GABA and glutamate were measured by high-performance liquid chromatography with electrochemical detection method.

RESULTS

Two weeks' treatment with FeTMPyP (3 mg/kg, i.p.) and 1,5-Isoquinolinediol (3 mg/kg, i.p.) improved the cognitive deficits in diabetic rats as observed in passive avoidance test. Both the agents inhibited lipid peroxidation and improves the acetylcholinesterase level in the hippocampus. 1,5-Isoquinolinediol treatment also improves the NAD, neurotransmitter level in the hippocampus.

DISCUSSION

These results suggest that peroxynitrite decomposition catalyst and PARP inhibitor have beneficial effects in neurobehavioral alterations induced by diabetes. Improvement in neurobehavioral alteration may be attributed to reversal of neurotransmitter homeostasis deficits.

Effects of GABAB receptor antagonists CGP63360, CGP76290A and CGP76291A on learning and memory processes in rodents

Data in literature that use methods for studying the learning and memory processes suggest that GABA and especially GABAB receptor antagonists may be active against amnesia. The aim of our study was to examine the effects of three new GABAB-antagonists on learning and memory processes. Active and passive avoidance tests with negative reinforcement in rats were used. The rats treated with different GABAB receptor antagonists showed improving effects in both tests (active and passive avoidances)on learning as well as on memory retention. There are some differences in their activities, probably due to its chemical structures. The phosphinic analogue CGP63360A is potent to the point that the benzoic one CGP76290A and the left isomer of the benzoic analogue CGP76291A has no effect. It may be concluded that the obtained results on the GABAB receptor antagonists could contribute to their pharmacological characteristics and might be of interest for potential clinical implication.

Cortistatin modulates memory processes in rats

Cortistatin (CST) is a recently described neuropeptide with high structural homology with somatostatin. Its mRNA is restricted to gamma amino butyric acid (GABA)-containing cells in the cerebral cortex and hippocampus. CST modulates the electrophysiology of the hippocampus and cerebral cortex of rats; hence, it may be modulating mnemonic processes. In this study, we have evaluated the effect of CST and somatostatin (SS) on short- and long-term memory (STM and LTM, respectively), as well as on the extinction of the behavior by using the footshock passive avoidance behavioral test. In addition, we tested the ability of both neuropeptides to affect the generation of cAMP in hippocampal neurons in culture. Results showed that the administration of either CST or SS into the hippocampal CA1 deteriorates memory consolidation in a dose-response fashion and facilitates the extinction of the learned behavior. CST was more potent than SS. Likewise, CST increases cAMP while SS decreases it. These results strongly support a modulatory role for CST in memory processes.