Biological Activity

Bioactivity / Mechanism

Atropine sulfate monohydrate functionally antagonized human M1 muscarinic receptor signaling in CHO-hM1 cells, inhibiting the calcium response to 3 μM carbachol with an IC50 of 48 nM. This cellular endpoint does not establish binding affinity or equivalent potency across M1–M5 receptors. [1]

Literature-reported observations and conditions; not Adooq-tested protocols or general treatment recommendations.

Target & Activity

Target	Activity	Value
mAChR		2.5 nM

In Vitro Studies

In isolated mouse retina, atropine sulfate monohydrate inhibited light-evoked ganglion-cell firing at high concentrations. At 0.5 μM, mean ON/OFF alpha-cell spike frequencies did not change significantly over 1–5 min, while an ON response appeared in two of six OFF cells. The experiment supports endpoint-specific effects rather than a general claim of unchanged retinal signaling. [2]

Functional antagonism of human M1-mediated calcium mobilization

Cell-based study · CHO cells stably expressing human M1 muscarinic acetylcholine receptors (CHO-hM1) [1]

Atropine inhibited carbachol-evoked calcium mobilization. This is a functional cellular IC50, not a binding affinity or an M1–M5 selectivity panel. HBSS did not attenuate the carbachol response; ATP and thapsigargin established assay responsiveness.

Measured endpoints — not treatment concentrations
Endpoint	Reported result	Reference
Inhibition of the calcium response to 3 μM carbachol in CHO-hM1 cells	Functional IC50 48 nM; n = 3 experiments in replicates of 4; curve data mean ± SEM	[1]

Literature-Reported Treatment Conditions

Treatment concentration: Atropine concentration-response series; carbachol challenge 3 μM.
Exposure duration: Antagonist added at recording time 60 s; agonist at 180 s; total recording 400 s.
Method: Fluo-4 calcium fluorescence assay at 25 °C; peak responses normalized to agonist maximum and fitted with a four-parameter logistic equation.
Vehicle: HBSS-based calcium assay buffer.
Co-treatment: Atropine pretreatment followed by carbachol; methylatropine and ethylatropine were separate comparators.
Reported limits: Exact antagonist concentration series is not tabulated in the text; no series is reconstructed from the graph. Lot stereochemical composition was not assayed in this experiment.

Methods and source locations

Compound reported in the paper: Atropine sulfate monohydrate; Compound label in the paper: Atropine sulfate monohydrate (Alfa Aesar)

Evidence applies to the reported atropine sulfate monohydrate material and stated experimental model. No equivalence of supplier lots, salt conversion or stereochemical assay is inferred.

Figure 2A–D and caption; Results human M1 assay; Methods Measurement of [Ca2+]i in CHO-hM1 Cells, Chemicals and Drugs, Data Analysis

Inhibition of the calcium response to 3 μM carbachol in CHO-hM1 cells: Fluo-4 fluorescence; concentration-response fit — Figure 2D and caption; Methods Data Analysis

Dose and time dependence of retinal ganglion-cell responses

Cell-based study · Isolated mouse retinal preparations; ON and OFF alpha retinal ganglion cells [2]

High concentrations inhibited light-evoked firing. At 0.5 μM, mean spike frequencies did not change significantly over 1–5 min, but ON responses appeared in a subset of OFF cells. A null frequency result therefore does not establish unchanged retinal information processing.

Measured endpoints — not treatment concentrations
Endpoint	Reported result	Reference
Normalized light-evoked spike frequency in ON alpha RGCs, relative to baseline 1	Normalized spike frequency 100 μM: 0.94 ± 0.18, p = 0.76; 300 μM: 0.57 ± 0.1, p = 0.048; 500 μM: 0.22 ± 0.08, p = 0.001; mean ± SEM, n = 5	[2]
Normalized light-evoked spike frequency after 5 min at 0.5 μM	Normalized spike frequency ON: 0.81 ± 0.1, n = 7, p = 0.11; OFF: 0.89 ± 0.05, n = 6, p = 0.28; mean ± SEM	[2]
Appearance of an ON response in OFF alpha RGCs after 5 min at 0.5 μM	Responder fraction 33.3% (two of six OFF alpha RGCs)	[2]

Literature-Reported Treatment Conditions

Treatment concentration: Direct retinal superfusion: high-dose series 100, 300 and 500 μM; separate time-course series 100, 10, 0.5 and 0.05 μM.
Exposure duration: Time-course recordings at 1, 3 and 5 min; 5-min wash in the high-dose experiment.
Method: Extracellular recordings under 525-nm full-field light stimulation (131 Rh* per rod/s); spike frequencies normalized within cells.
Vehicle: Mammalian Ringer’s solution.
Reported limits: The dwell time at each high-dose step in Figure 3 is not specified in the retrieved text. Mouse ex vivo exposures do not establish human retinal exposure or clinical safety.

Methods and source locations

Compound reported in the paper: Atropine sulfate monohydrate; Compound label in the paper: Atropine sulfate salt monohydrate (Sigma–Aldrich A-0257; reported MW 694.83)

Evidence applies to the reported atropine sulfate monohydrate material and stated experimental model. No equivalence of supplier lots, salt conversion or stereochemical assay is inferred.

Results dose- and time-dependent light-evoked responses; Figures 3–8 and captions; Methods Electrophysiology, Pharmacological Application of Atropine and GABA, Data Acquisition and Analysis

Normalized light-evoked spike frequency in ON alpha RGCs, relative to baseline 1: Extracellular recording; Student’s t-test — Results dose-dependent responses; Figure 3A–E,K and caption

Normalized light-evoked spike frequency after 5 min at 0.5 μM: Extracellular recording; Student’s t-test — Results time- and concentration-dependent responses, 0.5 μM paragraph; Figure 6I and caption

Appearance of an ON response in OFF alpha RGCs after 5 min at 0.5 μM: Light-evoked response histograms; subset response, not a change in mean OFF spike frequency — Results time- and concentration-dependent responses, 0.5 μM paragraph; Figure 7A–D and caption

In Vivo Studies

In form-deprived guinea pigs, daily peribulbar atropine sulfate monohydrate for two weeks reduced interocular myopia and axial elongation versus saline. Choroidal perfusion/thickness increased and scleral hypoxia-dependent labeling decreased. Residual myopia remained, and the associated vascular changes do not establish a causal pathway or clinical efficacy. [3]

Atropine in form-deprived guinea pigs

Animal study · Three-week-old pigmented guinea pigs; monocular right-eye form-deprivation myopia for two weeks; untreated fellow left eyes [3]

Atropine reduced, but did not eliminate, interocular myopia and axial elongation versus saline. Choroidal perfusion and thickness were higher, and hypoxia-dependent scleral labeling was lower. These associated endpoints do not identify the receptor subtype or prove that perfusion mediates atropine’s effect.

Measured endpoints — not treatment concentrations
Endpoint	Reported result	Reference
Treated-minus-fellow-eye refraction after two weeks	Interocular refraction difference Atropine −2.30 ± 1.31 D; saline −5.86 ± 2.73 D; P < 0.001; mean ± SD	[3]
Treated-minus-fellow-eye axial length after two weeks	Interocular axial length difference Atropine 0.08 ± 0.04 mm; saline 0.19 ± 0.05 mm; P < 0.001; mean ± SD	[3]
Choroidal perfusion/thickness and hypoxia-dependent scleral pimonidazole labeling	Directional responses Atropine-treated FDM eyes had higher choroidal thickness and perfusion than saline-treated FDM eyes (P < 0.001); interocular scleral hypoxia-labeling difference was lower with atropine (P < 0.05).	[3]

Conditions shared by the study groups

Route: Peribulbar injection, right eye
Frequency: Daily
Treatment course: Two weeks
Vehicle: Normal saline solution

Study groups and reported outcomes
Group / dose	Comparator	Observed result	Reference
FDM plus atropine 1 mg atropine in 100 µL solution	Saline-injected FDM right eyes compared between groups; left fellow eyes untreated in both groups.	Refraction and axial length differences remained myopic/positive but were smaller than saline controls.	[3]
FDM plus saline 100 µL solvent	Saline-injected FDM right eyes compared between groups; left fellow eyes untreated in both groups.	Greater myopia and axial elongation than atropine; lower choroidal perfusion and greater scleral hypoxia labeling.	[3]

FDM plus atropine: Model: Pigmented guinea pigs with monocular form deprivation; n = 14; Reported limits: Group totals from Experimental Design; no assumption that every endpoint used every animal. Sex not specified in the acquired Animals section.

FDM plus saline: Model: Pigmented guinea pigs with monocular form deprivation; n = 16; Reported limits: Group totals from Experimental Design; no assumption that every endpoint used every animal. Sex not specified in the acquired Animals section.

Methods and source locations

Compound reported in the paper: Atropine sulfate monohydrate; Compound label in the paper: Atropine sulfate monohydrate (≥97%; Stanford Chemicals)

Evidence applies to the reported atropine sulfate monohydrate material and stated experimental model. No equivalence of supplier lots, salt conversion or stereochemical assay is inferred.

Experiments 1.1.1–1.1.2; Figures 1A–D and 2A–E; Tables 1A–B; shared Material and Methods

Treated-minus-fellow-eye refraction after two weeks: Eccentric infrared photorefraction without cycloplegia; repeated-measures ANOVA with Bonferroni correction — Experiment 1.1.1; Figure 1A; Table 1A; Statistical Analysis

Treated-minus-fellow-eye axial length after two weeks: A-scan ultrasonography; repeated-measures ANOVA with Bonferroni correction — Experiment 1.1.1; Figure 1B; Table 1A; Statistical Analysis

Choroidal perfusion/thickness and hypoxia-dependent scleral pimonidazole labeling: OCTA motion-positive pixels (semiquantitative perfusion); pimonidazole immunofluorescence with antibody-omission and ischemic positive controls — Experiments 1.1.1–1.1.2; Figure 1C–D; Table 1B; Figure 2A–E and caption

FDM plus atropine · Experimental Design, Experiment 1; Pharmaceutical Preparation and Administration; Experiment 1.1.1; Figures 1–2

FDM plus saline · Experimental Design, Experiment 1; Pharmaceutical Preparation and Administration; Experiment 1.1.1; Figures 1–2

Specifications

Manufacturer	Adooq Bioscience
Actions	Antagonist
CAS Number	5908-99-6
Applications	mAChR antagonist
Formula	2(C17H23NO3).H2O.H2SO4
Molecular Weight	694.8
Synonyms	Atropisol; Atropt; Atropini sulfas; Tropine tropate
SMILES	CN1[C@H]2CC[C@@H]1C[C@@H](C2)OC(=O)C(CO)c3ccccc3.CN1[C@H]2CC[C@@H]1C[C@@H](C2)OC(=O)C(CO)c3ccccc3.O.OS(=O)(=O)O

Storage & Solubility

In Vitro Solubility

Reported Solubility

Solvent	Reported Solubility
DMSO	132 mg/mL (189.97 mM)
Water	132 mg/mL (189.97 mM)
Ethanol	132 mg/mL (189.97 mM)

Preparing Stock Solutions

Stock preparation is unavailable for this product molecular weight.

Calculated stock concentrations do not establish solvent solubility. Refer to the reported solubility data for experimental guidance.

Storage

Store powder at -20°C, keep desiccated.
In powder form, the chemical is stable for 36 months.
In solution, store at -20°C and use within 1 month to prevent loss of potency. Aliquot to avoid multiple freeze/thaw cycles.

Research References

[1] Rojas A, Ganesh T, Walker A, et al. Ethylatropine Bromide as a Peripherally Restricted Muscarinic Antagonist ACS chemical neuroscience (2017). PMID: 28044440 DOI: 10.1021/acschemneuro.6b00334 Source material
[2] Wang Q, Banerjee S, So C, et al. The Effect of Low-Dose Atropine on Alpha Ganglion Cell Signaling in the Mouse Retina Frontiers in cellular neuroscience (2021). PMID: 34025362 DOI: 10.3389/fncel.2021.664491 Source material
[3] Zhou X, Zhang S, Zhang G, et al. Increased Choroidal Blood Perfusion Can Inhibit Form Deprivation Myopia in Guinea Pigs Investigative ophthalmology & visual science (2020). PMID: 33211066 DOI: 10.1167/iovs.61.13.25 Source material

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Atropine sulfate monohydrate

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