PC12 Mutagenized cell variants reveal striking differences in the expression of Sodium channels and Nicotinic receptors when compared to wild-type PC12 cells. Even in the absence of nerve growth factor (NGF), the mutant cells express functional Na channels and Na channel mRNA at levels exceeding those in wild-type PC12 cells differentiated with NGF. In contrast, acetylcholine-induced currents were evident in only a small proportion of cells, presumably due to the altered pattern of expression of mRNAs encoding individual nAChR subunits. The altered ion channel expression in these variants provides an avenue for analyzing Na channel and nAChR channel function, as well as for identifying mechanisms governing their expression. https://link.springer.com/article/10.1007/BF00238418

Interactions in Dynamic reciprocity of sodium and potassium channel expression in a macromolecular complex involve Sigma-1 receptors. Such as Sigma-1 mediated regulation of ion currents interacting with various channels, like Kv1.2 channels, increasing their surface expression. Sigma-1 also inhibit Kv1.3, Kv1.4, and Kv1.5 channels. While regulating Kv2.1 channels, and inhibiting L-type voltage-gated calcium channels. Also inhibiting N-type Ca2+ channels currents. And inhibit voltage-gated sodium ion channels: Nav1.2/1.4 and Nav1.5. Sigma-1 regulate hERG channels while inhibiting acid-sensing ion channels (ASIC1a). https://www.sciencedirect.com/science/article/pii/S0149763421004796

NGF-dependent increase in phosphoinositide hydrolysis in PC12 cells is due to selective phosphorylation of PLC-gamma by serine and tyrosine protein kinases associated with the NGF receptor. https://www.sciencedirect.com/science/article/pii/S0021925818522997

Dose-Response Curve Stimulation by ATP gamma S of phospholipase C(PLC) was shifted to the right by the presence of UTP, indicating that both compounds act on the same receptors. Neuronal “nucleotide” receptor linked to phospholipase C and phospholipase D.

The lipase activity of PLCβ is not required for C3PO inhibition, and C3PO does not inhibit PLCβ. C3 Protein reduces neurite outgrowth and neuronal viability in vitro and restricts axon regeneration in vivo, and demonstrate a novel, non-traditional role for this inflammatory protein in the central nervous system.

PLCβ1 is strongly activated by Gαq. NGF added to PC12 cells remarkably increased PLCβ1 (i.e. 2.5–2.7-fold) in first 24 h. This increase peaks to 4-fold at 48 h (Fig. 1A) and decreases thereafter. Although Gαq also showed a large increase in expression with differentiation (1.6-fold), the onset of this increase was delayed 24 h relative to PLCβ

Alpha-7 Nicotinic Agonists or PAM both increased RhoA activity and inhibited neurite outgrowth. G-Protein Coupling is necessary for Alpha-7 Nicotinic mediated activated of RhoA. https://onlinelibrary.wiley.com/doi/epdf/10.1111/jnc.13660

Sigma-1 receptor agonist induces RhoA/ROCK activation. https://www.atherosclerosis-journal.com/article/S0021-9150(16)31056-5/abstract

Sigma-1 agonist significantly increased both β-catenin and ZO-1 levels. https://pmc.ncbi.nlm.nih.gov/articles/PMC7821090/

Wnt/β-catenin signaling plays an essential role in α7 nicotinic receptor-mediated neuroprotection. https://www.sciencedirect.com/science/article/abs/pii/S0006295217302848

Nicotinic ACh receptor activation decreases IL-1β secretion. stimulation of the evolutionarily ancient CHRNA7, CHRNA9, and/or CHRNA10 efficiently inhibit ATP-mediated secretion of IL-1β. The ATP-induced signaling cascade is regulated by nicotinic receptor stimulation. Phosphocholine and Phosphocholine-Modified Macromolecules modify many proteins and carbohydrates and reduce IL-1β. https://www.semanticscholar.org/paper/Phosphocholine-Modified-Macromolecules-and-Agonists-Hecker-Küllmar/e36c016ccf998540e4061f31581a91eae6feb780

Bromocytisine (3-BrCy) and 3-iodocytisine (3-ICy) exhibited increased binding affinity (especially at alpha7 nicotinic receptors; Ki approximately 0.1 microM) and functional potency. In addition, 3BrCy and 3-ICy increases intracellular Ca2+ in PC12 cells and inward currents in Xenopus oocytes expressing human alpha3beta4 nicotinic receptor (EC50 approximately 2 microM).

To examine the functional interaction between the sigma binding sites and nicotinic acetylcholine receptors, we investigated the effects of various sigma receptor ligands on nicotine-evoked Ca2+ uptake in differentiated PC12 cells. This study showed that PC12 cells express sigma 1-like sites and the inhibitory effect of sigma receptor ligands on the nicotine-evoked Ca2+ uptake was not directly coupled with either the sigma 1 or sigma 2 sites. https://www.sciencedirect.com/science/article/abs/pii/001429999600115X

https://www.nature.com/articles/35077000

Because nicotine can activate AKT via PI3K, we examined the protein levels of Bcl-2 and Bcl-x. We found that treatment with nicotine for 24 h increased the levels of Bcl-2 and Bcl-x, and this was inhibited by LY294002, which indicates the involvement of the PI3K pathway in nicotine-induced Bcl-2 and Bcl-x upregulation.

overexpression of Sig-1Rs significantly up-regulated Bcl-2. Overexpression of Bcl-2 member Mcl-1 in neurons enhanced surface expression of endogenous α7 nAChRs. Furthermore, the activity of several other neuronal nAChR subtypes is also enhanced by NACHO17. Biochemical studies show that NACHO mediates α7 pentamer formation, as NACHO is required for receptor labeling by α-bungarotoxin (α-Bgt)16, which binds at the interface between assembled α7 subunits4,18. Interestingly, resistance to inhibitors of cholinesterase-3 (Ric-3) protein, which is required for nAChR function in Caenorhabditis elegans19, synergizes with NACHO to promote receptor assembly and function16. https://www.nature.com/articles/s41467-019-10723-x

In this manuscript, we demonstrate that S1R is required for biosynthesis of the Atg8 family proteins LC3B, GABARAP, and GABARAPL2. Cells lacking SIGMAR1 show reduced levels of many Atg8-family proteins and impaired autophagic flux.

The intra-α subunit ECD-TMD interface is important to channel function in both human adult and Torpedo nAChR. The transmembrane domain (TMD) of α7nAChR has been identified as a target for positive allosteric modulators (PAMs). https://www.nature.com/articles/s41467-024-46028-x

demonstrating that Nkcc1 overexpression in adult mice restored plasticity to a similar level as observed in the juvenile brain. Activation of TRPV1 by exogenous agonists can increase the expression and function of NKCC1 protein in DRG, which is mediated by activation of PKC/p-ERK signaling pathway. Sigma-1 σ-1 receptor activation inhibits glutamate release from rat cortical nerve terminals. This effect is linked to a decrease in Ca²⁺ caused by Ca²⁺ entry through presynaptic voltage-dependent Ca²⁺ channels and the suppression of the PKC signaling cascade. Furthermore,results suggest that DRG NKCC1 may participate in the inflammatory pain induced by TRPV1. Pursuant to its local anesthetic properties we have shown, for the first time, that nicotine inhibits TTX-resistant sodium channels. In addition, we have also shown, for the first time, that nicotine sensitizes responses to TRPV1 receptors. https://journals.physiology.org/doi/full/10.1152/jn.00922.2003

In all types of nAChRs, agonists such as ACh itself or nicotine-induced ion channel opening and evoke influx of Na+ and Ca2. Sodium-Channel literature results are consistent with the idea of a sigma-1 protein behaving like either a "chaperone" or a regulatory subunit associated with nNav1.5. Increasing sigma-1 expression to the cells reduced the surface expression of nNav1.5 protein. https://pubmed.ncbi.nlm.nih.gov/23139844/

It is unlikely that nicotine-induced protection against glutamate neurotoxicity is due to its direct action on NMDA receptors though there are some reports indicating that nicotine partially inhibits NMDA receptors. The sigma-1 receptor modulates NMDA receptor synaptic transmission and plasticity via SK channels in rat hippocampus. Overall, results indicate that Ca2+influx through post-synaptic NMDARs is required for the σR-1 activation to exert the enhancement of the NMDAR currents.

nAChRs, especially α7 nAChRs, generate specific and complex Ca2+ signals that include adenylyl cyclase, protein kinase A, protein kinase C, Ca2+-calmodulin-dependent kinase, and phosphatidylinositol 3-kinase (PI3K). Sigma-1, residing mainly at the mitochondria-associated Endoplasmic-Reticulum (ER) membrane (MAM), where it chaperones IP3R3 to ensure proper Ca2+ signaling from the endoplasmic reticulum into mitochondria.

The nuclear pore complex (NPC) has been coined “The gate to neurodegenerative diseases”58. Here we report the existence of the first molecular chaperone at the NPC and show that this chaperone, the Sig-1R(Sigma-1 Receptor), being therapeutic for ALS patients. Firstly, we used a human cell line here in the present study. Secondly, we have shown in the past that results from cell lines perfectly mimic the results from rodent brain39,59. https://www.nature.com/articles/s41467-020-19396-3

Immunohistochemistry showed marked loss of nuclear TDP-43, was accompanied by reduction of choline acetyltransferase (ChAT). Choline O-acetyltransferase) is an important enzyme catalyzing the transfer of acetyl group from Acetyl-CoA to choline for synthesis of acetylcholine (ACh), which is a major neurotransmitter in the brain. SIGMAR1 was consistently shown to be co-localized with neuronal nuclear inclusions in TDP-43 proteinopathy, five polyglutamine diseases and INIBD, as well as in intranuclear Marinesco bodies in aged normal controls.

Young hippocampal neurons in α7 nicotinic KO mice have a prolonged period of GABAergic excitation because of delayed appearance of the mature chloride transporter KCC2 and extended presence of the immature chloride transporter NKCC1.

These results suggest that antinociceptive effects of α7 nAChR PAM are associated with downregulation of hippocampal BDNF and p-NKCC1 and upregulation of KCC2 in a mouse model of inflammatory pain. Respectively, nicotine and neurotrophins show similar properties in terms of time-course and signal pathways of neuroprotection. https://www.ncbi.nlm.nih.gov/books/NBK543551/

Results suggest that activation of cholinergic pathway(both muscarinic and nicotinic) restores GABAergic driving force and temporal order recognition deficits in Ngfr−/− (NERVE GROWTH FACTOR KNOCKOUT) mice. Stimulation at sigma-1 receptors by sigma-1 receptor agonists and subsequent interaction with IP3 receptors are involved in the mechanism underlying the potentiation of NGF-induced neurite outgrowth by sigma-1 receptor agonists. https://pmc.ncbi.nlm.nih.gov/articles/PMC2435603/

Hello everyone,

I'm researching the neurochemical dynamics between the monoamine oxidase inhibiting harmala alkaloids present in Banisteriopsis caapi (the MAOI component in ayahuasca) and gabapentinoids, specifically pregabalin (Lyrica) and gabapentin (Neurontin). My interest is in understanding any potential pharmacological interactions or contraindications, particularly from a safety perspective.

According to Dr Benjamin Malcolm's 2023 UConn School of Pharmacy presentation on ayahuasca drug interactions, gabapentinoids such as pregabalin and gabapentin are generally considered low-risk when combined with ayahuasca. This categorisation is based on their lack of binding to monoamine reuptake pumps or release of monoamines (such as 5HT, NE, and DA), which are crucial factors in the risk profile for serotonergic drugs combined with MAOIs. However, given pregabalin's mechanism as an α2δ subunit ligand of voltage-gated calcium channels and its sedative properties that share some similarities with benzodiazepines, I wonder if there might still be nuanced interactions worth exploring, even in the absence of direct serotonergic activity.

Specifically, I'm interested in theoretical safety risks regarding potential CNS depressant effects or subtle alterations in neurochemical stability during the ayahuasca experience. While Dr. Malcolm's presentation suggests a lack of life-threatening interactions, the question remains whether pregabalin might modulate the subjective or physiological response to ayahuasca or present secondary risks in any capacity.

I would greatly appreciate your insights if anyone has encountered additional research, pharmacological theories, or public case studies exploring this interaction. I'd also welcome any perspectives on the pharmacodynamic implications of combining these substances.

Thanks in advance for your input!

Source: Ayahuasca Drug Interactions (Malcolm, 2023) - University of Connecticut School of Pharmacy

Hey!

I just found this paper from a couple days ago.

https://molpharm.aspetjournals.org/content/early/2024/08/26/molpharm.124.000947.long

The scientists postulate that ketamine, norketamine and 6-hydroxynorketamine act as a positive allosteric modulator (PAM) of all opioid receptors at nanomolar concentrations. At micromolar concentrations it acts as a full agonist.

As a PAM ketamine (and metabolites) enhance endogenous opioid signalling through endorphins, in contrast to morphine - which activates all opioid receptors, regardless of endogenous peptide signalling. This, according to the authors, might be one reason for it's differential efficacies in MDD.

This, to them, seems to unify some conflicting data as to whether the opioid system takes part in the antidepressant actions. Moreover, they go a step closer to elucidating the rapid but short-lasting antidepressant effect of ketamine -> half-lives of major metabolites.

I'm really not deep into ketamine pharmacology, but I've heard about conflicts in the past regarding whether naltrexone/naloxone inhibit antidepressant actions and to which extent the opioid system takes part in therapeutic efficacy.

Would be great to hear what you guys think, especially those of you that are deeper in the topic!

Hey!

I haven't seen much on the reversible MAO-B inhibitor (and anticonvulsant) safinamide here. Why is that?

In this letter to the editor (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10983021/) they mention the following:

"Despite the promise of MAO‐B inhibitors in treating brain diseases, a limitation of drugs like selegiline (L‐deprenyl) is their effects are not long‐lasting. In APP/PS1 mice, selegiline showed a therapeutic effect lasting approximately one week, but this effect diminished with long‐term administration of about four weeks. Notably, prolonged use of selegiline triggered a compensatory mechanism involving diamine oxidase (DAO)‐dependent GABA synthesis, a pathway alternative to MAO‐B that degrades putrescine into GABA. As an irreversible MAO‐B inhibitor, selegiline forms a covalent bond with MAO‐B, eventually destroying it and subsequently activating the compensatory mechanism (i.e. DAO‐dependent GABA synthesis). On the other hand, reversible MAO‐B inhibitors such as safinamide (Xadago) and the newly developed KDS2010 (Tisolagiline) have less compensatory effects because they compete with the substrate and consequently leave MAO‐B intact. This contrast strongly suggests the use of reversible, but not irreversible, MAO‐B inhibitors as a long‐term treatment to reduce MAO‐B‐dependent GABA synthesis in pathological conditions."

I had found this info in a proper paper as well, but I can't seem to find it anymore - PubMed really has a bad search function imho.

While not fully elucidated in humans, I believe, tonic GABA increase (through astrocytes) seems to be related with MDD as well (in mice afaik):

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7408154/

https://www.mdpi.com/2073-4409/13/4/318

So there might be merit to avoiding compensatory DAO activation in MDD?

From what I could see "Safinamide is vastly more selective for MAO-B than MAO-A (1,000 times more selective in humans), when compared with rasagiline (203 times) or selegiline (127 times)." (https://www.dovepress.com/safinamide-in-the-management-of-patients-with-parkinsonrsquos-disease--peer-reviewed-fulltext-article-TCRM).

And "Single oral administration of safinamide at 600 μg/kg (36 mg for a 60-kg subject) inhibited 91% of platelet MAO-B activity in a few hours, and a steady-state plasma concentration of safinamide could be achieved with only five days of repeated daily administration" (https://www.sciencedirect.com/science/article/pii/S0022510X2030349X).

From what I could see, safinamide has low to mid nanomolar affinity to MAO-B and sigma 1, while having mid micromolar affinities to voltage gated calcium and sodium channels (like lamotrigine/lamictal) and tendentially NDRI properties. At 100 mg/day it seems to affect the ion channels, while at 50 mg/day it does not, though inhibiting MAO-B to a similar extent. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10479837/)

This sounds to me like a very interesting combination of properties and I'm wondering why it's not discussed more - as augmentation of existing AD drugs or as a standalone therapy.

I believe I read it on here somewhere, but there's data suggesting high doses of moclobemide (900-1200 mg) being more efficacious than common doses (300-600 mg). This could be explained by that one PET trial (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4772270/) showing only around 75% occupancy at common doses and 85% at high doses (comparable to occupancy of irreversibles) or maybe even of moclobemide losing its selectivity at those doses and also partially inhibiting MAO-B (analogous to selegiline losing its selectivity at high doses used for MDD)?

Wouldn't a common dose of moclobemide + 50 mg (or lower even?) of safinamide then have a similar effect? Has anybody looked into this? To me this sounds like a safer (regarding dietary restrictions) alternative to common unselective irreversible MAOIs.

Looking forward to your thoughts!