The role of interaction between orexin receptors and β2 adrenergic receptors in basolateral amygdala in dentate gyrus synaptic plasticity in male rats

Olfactory receptors in neural regeneration in the central nervous system

Olfactory receptors are crucial for detecting odors and play a vital role in our sense of smell, influencing behaviors from food choices to emotional memories. These receptors also contribute to our perception of flavor and have potential applications in medical diagnostics and environmental monitoring. The ability of the olfactory system to regenerate its sensory neurons provides a unique model to study neural regeneration, a phenomenon largely absent in the central nervous system. Insights gained from how olfactory neurons continuously replace themselves and reestablish functional connections can provide strategies to promote similar regenerative processes in the central nervous system, where damage often results in permanent deficits. Understanding the molecular and cellular mechanisms underpinning olfactory neuron regeneration could pave the way for developing therapeutic approaches to treat spinal cord injuries and neurodegenerative diseases like Alzheimer's disease. Olfactory receptors are found in almost any cell of every organ/tissue of the mammalian body. This ectopic expression provides insights into the chemical structures that can activate olfactory receptors. In addition to odors, olfactory receptors in ectopic expression may respond to endogenous compounds and molecules produced by mucosal colonizing microbiota. The analysis of the function of olfactory receptors in ectopic expression provides valuable information on the signaling pathway engaged upon receptor activation and the receptor's role in proliferation and cell differentiation mechanisms. This review explores the ectopic expression of olfactory receptors and the role they may play in neural regeneration within the central nervous system, with particular attention to compounds that can activate these receptors to initiate regenerative processes. Evidence suggests that olfactory receptors could serve as potential therapeutic targets for enhancing neural repair and recovery following central nervous system injuries.

Divergent effects of noradrenergic activation and orexin receptor 1 blockade on hippocampal structure, anxiety-like behavior, and social interaction following chronic stress

Chronic stress (Ch.S) has detrimental effects on the brain's structure and function, particularly in the hippocampus. The noradrenergic and orexinergic systems play crucial roles in the stress response and regulation of stress-related behaviors. This study aimed to investigate the interaction between noradrenergic activation and orexin receptor 1 inhibition on chronic stress-induced hippocampal alterations. The study conducted experiments on male Wistar rats, subjected to Ch.S, OXr1 blocking, noradrenergic activation, or a combination of these treatments. Plasma corticosterone level was measured using a fluorometric method. Behavioral assessment of social maze, elevated plus maze (EPM) and novel object recognition (NOR) test were performed. Then, the expression of prepro-orexin, OXr1, and glucocorticoid receptor (GR) was analyzed using semiquantitative RT-PCR. Neuronal populations were quantified through Nissl staining. The data revealed that all stress and yohimbine groups had elevated plasma corticosterone levels. Ch.S significantly altered behavior, impairing social interaction, disrupting object recognition memory and increasing anxiety-like responses in the EPM. OXr1 blocking reversed these stress-induced behavioral deficits, while yohimbine did not improve these behavioral outcomes. Chronic stress led to a significant increase in prepro-orexin, OXr1, and GR expression. While blocking OXr1 helped counteract these stress-induced changes, yohimbine failed to restore the expression levels. Ch.S reduced hippocampal neuronal populations, while OXr1 blocking partially reversed this effect, and yohimbine further recovered the reversal. These findings indicate that blocking hippocampal OXr1 can mitigate the adverse effects of chronic stress on both hippocampal structure and anxiety-like behaviors, while noradrenergic signaling appears to have differential effects on behavioral and cellular measures.

Orexin neuropeptides modulate the hippocampal-dependent memory through basolateral amygdala interconnections

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Orexin neuropeptides roles in hippocampal-dependent memory formation.

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Orexin neuropeptides activate the neural circuits of the basolateral amygdala.

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The power of memorization is modulated by the level of orexin neuropeptides.

Orexin neuropeptides have functional roles in hippocampal-dependent memory formation via the consolidation and retrieval of passive avoidance and spatial memories. The effects of these neuropeptides have been confirmed on the induction of long-term potentiation (LTP). The orexinergic system seems to have modulatory effects by sending projection fibers to several brain parts, such as the hippocampus and amygdala. Orexin neuropeptides activate the neural circuits of the basolateral amygdala during different arousal events with various emotional loads. Therefore, this system plays a vital role in creating appropriate behavioral reactions and responses particular to the situation. This review aimed to report new progression and advances in the hippocampus function in memory by focusing on its relationship with the amygdala through the orexinergic system.