Dronedarone Modulates M1 and M3 Muscarinic Receptors with Subtype Selectivity, Functional Selectivity, and Probe Dependence

Hybrid Allosteric Modulators of M1 Muscarinic Receptors Enhance Acetylcholine Efficacy and Decrease Locomotor Activity and Turning Behaviors in Zebrafish

Allosteric modulation of muscarinic acetylcholine receptors (mAChR) has been identified as a potential strategy for regulating cholinergic signaling in the treatment of various neurological disorders. Most positive allosteric modulators (PAMs) of mAChR enhance agonist affinity and potency, while very few PAMs selectively enhance G-protein coupling efficacy (e.g., amiodarone). The key structural features of amiodarone responsible for enhancement of mAChR efficacy were examined in CHO cells expressing M1 receptors. Subsequent incorporation of these structural features into previously identified allosteric modulators of potency (i.e., n-benzyl isatins) generated hybrid ligands that demonstrated similar or better enhancement of mAChR efficacy, lower in vivo toxicity, and higher allosteric binding affinity relative to amiodarone. Notable hybrid ligands include 8a and 8b which respectively demonstrated the strongest binding affinity and the most robust enhancement of mAChR efficacy as calculated from an allosteric operational model. Amiodarone derivatives and hybrid ligands were additionally screened in wildtype zebrafish (Danio rerio) to provide preliminary in vivo toxicity data as well as to observe effects on locomotor and turning behaviors relative to other mAChR PAMs. Several compounds, including 8a and 8c, reduced locomotor activity and increased measures of turning behaviors in zebrafish, suggesting that allosteric modulation of muscarinic receptor efficacy might be useful in the treatment of repetitive behaviors associated with autism spectrum disorder (ASD) and other neuropsychiatric disorders.

Is Low Heart Rate Variability Associated with Emotional Dysregulation, Psychopathological Dimensions, and Prefrontal Dysfunctions? An Integrative View

Several studies have suggested a correlation between heart rate variability (HRV), emotion regulation (ER), psychopathological conditions, and cognitive functions in the past two decades. Specifically, recent data seem to support the hypothesis that low-frequency heart rate variability (LF-HRV), an index of sympathetic cardiac control, correlates with worse executive performances, worse ER, and specific psychopathological dimensions. The present work aims to review the previous findings on these topics and integrate them from two main cornerstones of this perspective: Porges' Polyvagal Theory and Thayer and Lane's Neurovisceral Integration Model, which are necessary to understand these associations better. For this reason, based on these two approaches, we point out that low HRV is associated with emotional dysregulation, worse cognitive performance, and transversal psychopathological conditions. We report studies that underline the importance of considering the heart-brain relation in order to shed light on the necessity to implement psychophysiology into a broader perspective on emotions, mental health, and good cognitive functioning. This integration is beneficial not only as a theoretical ground from which to start for further research studies but as a starting point for new theoretical perspectives useful in clinical practice.

Cholinergic System and Its Therapeutic Importance in Inflammation and Autoimmunity

Neurological and immunological signals constitute an extensive regulatory network in our body that maintains physiology and homeostasis. The cholinergic system plays a significant role in neuroimmune communication, transmitting information regarding the peripheral immune status to the central nervous system (CNS) and vice versa. The cholinergic system includes the neurotransmitter\ molecule, acetylcholine (ACh), cholinergic receptors (AChRs), choline acetyltransferase (ChAT) enzyme, and acetylcholinesterase (AChE) enzyme. These molecules are involved in regulating immune response and playing a crucial role in maintaining homeostasis. Most innate and adaptive immune cells respond to neuronal inputs by releasing or expressing these molecules on their surfaces. Dysregulation of this neuroimmune communication may lead to several inflammatory and autoimmune diseases. Several agonists, antagonists, and inhibitors have been developed to target the cholinergic system to control inflammation in different tissues. This review discusses how various molecules of the neuronal and non-neuronal cholinergic system (NNCS) interact with the immune cells. What are the agonists and antagonists that alter the cholinergic system, and how are these molecules modulate inflammation and immunity. Understanding the various functions of pharmacological molecules could help in designing better strategies to control inflammation and autoimmunity.