Additive effect of BLA GABAA receptor mechanism and (+)-MK-801 on memory retention deficit, an isobologram analysis

Amygdala activity and amygdala-hippocampus connectivity: Metabolic diseases, dementia, and neuropsychiatric issues

With rapid aging of the population worldwide, the number of people with dementia is dramatically increasing. Some studies have emphasized that metabolic syndrome, which includes obesity and diabetes, leads to increased risks of dementia and cognitive decline. Factors such as insulin resistance, hyperglycemia, high blood pressure, dyslipidemia, and central obesity in metabolic syndrome are associated with synaptic failure, neuroinflammation, and imbalanced neurotransmitter levels, leading to the progression of dementia. Due to the positive correlation between diabetes and dementia, some studies have called it "type 3 diabetes". Recently, the number of patients with cognitive decline due to metabolic imbalances has considerably increased. In addition, recent studies have reported that neuropsychiatric issues such as anxiety, depressive behavior, and impaired attention are common factors in patients with metabolic disease and those with dementia. In the central nervous system (CNS), the amygdala is a central region that regulates emotional memory, mood disorders, anxiety, attention, and cognitive function. The connectivity of the amygdala with other brain regions, such as the hippocampus, and the activity of the amygdala contribute to diverse neuropathological and neuropsychiatric issues. Thus, this review summarizes the significant consequences of the critical roles of amygdala connectivity in both metabolic syndromes and dementia. Further studies on amygdala function in metabolic imbalance-related dementia are needed to treat neuropsychiatric problems in patients with this type of dementia.

The Roles of Optogenetics and Technology in Neurobiology: A Review

Optogenetic is a technique that combines optics and genetics to control specific neurons. This technique usually uses adenoviruses that encode photosensitive protein. The adenovirus may concentrate in a specific neural region. By shining light on the target nerve region, the photosensitive protein encoded by the adenovirus is controlled. Photosensitive proteins controlled by light can selectively allow ions inside and outside the cell membrane to pass through, resulting in inhibition or activation effects. Due to the high precision and minimally invasive, optogenetics has achieved good results in many fields, especially in the field of neuron functions and neural circuits. Significant advances have also been made in the study of many clinical diseases. This review focuses on the research of optogenetics in the field of neurobiology. These include how to use optogenetics to control nerve cells, study neural circuits, and treat diseases by changing the state of neurons. We hoped that this review will give a comprehensive understanding of the progress of optogenetics in the field of neurobiology.

Amygdala-hippocampal interactions in synaptic plasticity and memory formation

Memories of emotionally arousing events tend to endure longer than other memories. This review compiles findings from several decades of research investigating the role of the amygdala in modulating memories of emotional experiences. Episodic memory is a kind of declarative memory that depends upon the hippocampus, and studies suggest that the basolateral complex of the amygdala (BLA) modulates episodic memory consolidation through interactions with the hippocampus. Although many studies in rodents and imaging studies in humans indicate that the amygdala modulates memory consolidation and plasticity processes in the hippocampus, the anatomical pathways through which the amygdala affects hippocampal regions that are important for episodic memories were unresolved until recent optogenetic advances made it possible to visualize and manipulate specific BLA efferent pathways during memory consolidation. Findings indicate that the BLA influences hippocampal-dependent memories, as well as synaptic plasticity, histone modifications, gene expression, and translation of synaptic plasticity associated proteins in the hippocampus. More recent findings from optogenetic studies suggest that the BLA modulates spatial memory via projections to the medial entorhinal cortex, and that the frequency of activity in this pathway is a critical element of this modulation.

The effect of GABA-B receptors in the basolateral amygdala on passive avoidance memory impairment induced by MK-801 in rats

MK-801 (dizocilpine) is a potent non-competitive N-methyl-[D]-aspartate (NMDA) receptor antagonist that affects cognitive function, learning, and memory. As we know, NMDA receptors are significantly involved in memory function, as well as GABA (Gamma-Aminobutyric acid) receptors. In this study, we aimed to discover the effect of GABA-B receptors in the basolateral amygdala (BLA) on MK-801-induced memory impairment. We used 160 male Wistar rats. The shuttle box was used to evaluate passive avoidance memory and locomotion apparatus was used to evaluate locomotor activity. MK-801 (0.125, 0.25, and 0.5 μg/rat), baclofen (GABA-B agonist, 0.0001, 0.001, and 0.01 μg/rat) and phaclofen (GABA-B antagonist, 0.0001, 0.001, and 0.01 μg/rat) were injected intra-BLA, after the training. The results showed that MK-801 at the dose of 0.5 μg/rat, baclofen at the doses of 0.001 and 0.01 μg/rat, and phaclofen at the doses of 0.001 and 0.01 μg/rat, impaired passive avoidance memory. Locomotor activity did not alter in all groups. Furthermore, the subthreshold dose of both baclofen (0.0001 μg/rat) and phaclofen (0.0001 μg/rat) restored the impairment effect of MK-801 (0.5 μg/rat) on memory. Also, both baclofen (0.0001 μg/rat) potentiated the impairment effect of MK-801 (0.125 μg/rat) and phaclofen (0.0001 μg/rat) potentiated the impairment effect of MK-801 (0.125 and 0.25 μg/rat) on passive avoidance memory. In conclusion, our results indicated that BLA GABA-B receptors can alter the effect of NMDA inactivation on passive avoidance memory.

Better antidepressant efficacy of mecamylamine in combination with L-NAME than with L-arginine

Aff ;ective disorders, including anxiety and mood disorders, are a constellation of psychiatric diseases that aff ;ect over 10 % of the world's population. It has been proposed that drugs that change nicotinic acetylcholine receptor (nAChR) activity can affect mood- and anxiety-related behaviors. Also, neuronal nitric oxide synthase (nNOS) is closely associated with the pathophysiology of these disorders. To limit the potential adverse effects of alteration in cholinergic and nitric oxide (NO) systems, we investigated the combined efficacy of subthreshold doses of nAChR antagonist mecamylamine and NO ligands (L-arginine as agonist and l-NAME as an antagonist) on depression- and anxiety-related behaviors in male NMRI mice. Depression-related behaviors using the forced swim test (FST) and anxiety-like activity using the hole-board test were assessed. In our results, mecamylamine (3 mg/kg) showed antidepressant-like properties, and it also tended to have anxiolytic-like effects, though not significant. Concomitant treatment of subthreshold doses of mecamylamine (1 mg/kg) and l-arginine (25 mg/kg), l-NAME (1 mg/kg), or l-arginine/L-NAME were antidepressive. In contrast, l-arginine/L-NAME alone or in associated with mecamylamine showed anxiogenic-like efficacy. Isobolographic analysis exhibited an additive antidepressant effect of the combined subthreshold doses of mecamylamine and l-arginine, and a synergistic antidepressant effect of the combined subthreshold doses of mecamylamine and l-NAME. It should be noted that mecamylamine (3 mg/kg) elicited hypolocomotion. Our results suggest that mecamylamine produces a better antidepressant efficacy in combination with l-NAME than with l-arginine.

Additive interaction between scopolamine and nitric oxide agents on immobility in the forced swim test but not exploratory activity in the hole-board

RATIONALE

The muscarinic cholinergic antagonist scopolamine has received an attention due to its unique antidepressant effects. However, the considerable adverse effects on nervous system limit the use of scopolamine as a psychiatric drug.

OBJECTIVE

In order to overcome the limitations and increase the therapeutic effects of scopolamine, we decided to examine the effects of joint administration of sub-effective dose of scopolamine and the sub-effective dose of a nitric oxide (NO) precursor L-Arginine or a non-selective nitric oxide synthase (NOS) inhibitor L-NAME on depression- and anxiety-related behaviors in male NMRI mice.

METHODS

To this aim, animal behavior was assessed in the forced swim test (FST) and hole-board apparatus.

RESULTS

Scopolamine (0.05 mg/kg) significantly decreased immobility time in the FST, suggesting an antidepressant-like effect. Moreover, L-Arginine (50 mg/kg) produced an antidepressant-like response in the FST and decreased head-dip counts in the hole-board apparatus, indicating an anxiety-like effect. The same doses of scopolamine and L-Arginine decreased the locomotor activity in mice. Joint administration of sub-effective dose of scopolamine (0.01 mg/kg) with a low dose of L-Arginine (25 mg/kg) or L-NAME (1 mg/kg) induced a profound antidepressant-like effect in the FST. These drug combinations did not influence on anxiety-related behaviors. Meanwhile, L-NAME alone did not alter the performance of mice in the FST and hole-board. Isobolographic analysis revealed an additive effect for scopolamine and L-Arginine or L-NAME.

CONCLUSION

Data suggests that NO agents could positively impact the therapeutic profile of scopolamine, because they might be useful for inducing antidepressant-like effect associated to scopolamine.

Isobologram Analysis: A Comprehensive Review of Methodology and Current Research

Drug combination is a common method for clinical disease treatment. Whether the combination of drugs is reasonable often affects the result of the disease treatment. Many methods have been used to evaluate interaction between drugs to date. Isobologram analysis has been mathematically proven and widely used to evaluate drug interactions. In this paper, the principle of isobologram analysis and its application in drug interaction evaluation are summarized. The applications of the similar cotoxicity coefficient and fractional inhibitory concentration index in the evaluation of drug interaction are also reviewed. This work is expected to evaluate the effect of formulations scientifically and provide scientific judgment standards for the development of formulations and clinical drug compatibility.