(-)-Scopolamine Hydrobromide Trihydrate: Properties & Uses

(-)-Scopolamine hydrobromide trihydrate is a water-soluble hydrobromide salt of the naturally occurring tropane alkaloid scopolamine, isolated from Solanaceae family plants, and widely used in research as a competitive muscarinic acetylcholine receptor antagonist with notable selectivity for the M1 subtype.

Chemical Form

Hydrobromide salt trihydrate of (-)-Scopolamine

Natural Source

Isolated from plants of the Solanaceae family

Primary Mechanism

Competitive inhibition of acetylcholine muscarinic receptors

Receptor Selectivity

Selective for muscarinic acetylcholine receptor subtype M1 (mAChR M1)

Pharmacological Class

Anticholinergic / Parasympatholytic agent

Key Research Application

Studies of parasympathetic nervous system functioning and cholinergic signaling

Chemical Identity and Origin

(-)-Scopolamine hydrobromide trihydrate is the hydrobromide salt form of scopolamine, a tropane alkaloid naturally occurring in plants belonging to the Solanaceae family, which includes genera such as Datura, Hyoscyamus, and Scopolia. The trihydrate designation indicates that three molecules of water are incorporated into the crystal lattice, which influences the compound's physical handling characteristics and molecular weight calculations relevant to solution preparation.

The salt form confers improved water solubility compared to the free base, making (-)-Scopolamine hydrobromide trihydrate particularly amenable to preparation of aqueous stock solutions for in vitro and in vivo research applications. Researchers should account for the trihydrate water content when calculating molar concentrations.

Mechanism of Action: Anticholinergic Activity

Scopolamine exerts its pharmacological effects through competitive inhibition of muscarinic acetylcholine receptors (mAChRs). By competing with the endogenous neurotransmitter acetylcholine at these receptors, scopolamine prevents cholinergic signal transduction without activating the receptor itself, classifying it as a competitive antagonist.

Among the five known muscarinic receptor subtypes (M1–M5), scopolamine demonstrates selectivity for the M1 subtype (mAChR M1), which is predominantly expressed in the central nervous system, including the cerebral cortex and hippocampus, as well as in autonomic ganglia. This M1 selectivity is particularly relevant to studies investigating cognitive function, memory, and learning, where cholinergic neurotransmission plays a well-established role.

Suppression of the cholinergic response downstream of mAChR inhibition results in decreased activity of the parasympathetic nervous system, producing characteristic anticholinergic effects that are leveraged in experimental models of parasympathetic dysfunction.

Research Applications

(-)-Scopolamine hydrobromide trihydrate is widely exploited as a pharmacological tool in neuroscience and pharmacology research. Its primary utility lies in the experimental induction of cholinergic deficits, allowing researchers to model conditions associated with impaired muscarinic signaling.

Cognitive and Memory Research: Systemic or central administration of scopolamine is a well-established method for producing transient amnesia and cognitive impairment in animal models, facilitating the study of cholinergic contributions to learning and memory processes. This scopolamine-induced amnesia model is frequently used to evaluate the efficacy of potential procognitive or nootropic compounds.

Parasympathetic Nervous System Studies: Because inhibition of mAChRs broadly suppresses parasympathetic tone, scopolamine is employed to investigate the role of the parasympathetic branch of the autonomic nervous system in various physiological processes, including gastrointestinal motility, cardiovascular regulation, and glandular secretion.

Motion Sickness and Nausea Models: Scopolamine's antiemetic properties, mediated through central muscarinic receptor blockade, make it relevant to research on vestibular function and motion sickness models.

Handling, Solubility, and Storage Guidance

Solubility: The hydrobromide trihydrate salt form of scopolamine is freely soluble in water and soluble in ethanol, facilitating straightforward preparation of stock solutions. Researchers should prepare solutions using the molecular weight of the trihydrate form to ensure accurate molar concentrations.

Storage: As with most alkaloid salts, (-)-Scopolamine hydrobromide trihydrate should be stored in a cool, dry place, protected from light and moisture. Specific storage temperature recommendations should be confirmed from the product certificate of analysis (CoA) provided with each lot.

Safety: Standard laboratory precautions should be observed when handling this compound. As an anticholinergic agent, it may cause physiological effects upon exposure via skin absorption, inhalation, or ingestion. Appropriate personal protective equipment (PPE) including gloves and eye protection should be worn. Researchers should consult the Safety Data Sheet (SDS) for full hazard information prior to use.

Frequently asked questions

What is the difference between scopolamine free base and (-)-Scopolamine hydrobromide trihydrate?

The free base form of scopolamine has limited water solubility, whereas the hydrobromide salt trihydrate is freely water-soluble, making it significantly easier to prepare aqueous solutions for biological assays. The trihydrate designation indicates the presence of three water molecules in the crystal structure, which must be accounted for in molecular weight calculations when preparing molar stock solutions.

Why is mAChR M1 selectivity important for research applications of scopolamine?

mAChR M1 receptors are highly expressed in brain regions associated with cognition and memory, including the hippocampus and cortex. Scopolamine's relative selectivity for M1 makes it a valuable tool for dissecting the contribution of this specific receptor subtype to cholinergic-dependent cognitive processes, and for constructing pharmacological amnesia models used in drug discovery research.

How should (-)-Scopolamine hydrobromide trihydrate stock solutions be prepared and stored?

Stock solutions are best prepared by dissolving the compound in water or aqueous buffer, using the molecular weight of the trihydrate form for accurate concentration calculations. Aliquots should be stored at the temperature specified on the product CoA, protected from light, and freeze-thaw cycles should be minimized to maintain stability. Consult the SDS and CoA provided with the specific lot for authoritative guidance.

What experimental models commonly use scopolamine as a pharmacological tool?

Scopolamine is most commonly used in rodent behavioral models to induce transient cognitive impairment and amnesia, serving as a benchmark model for evaluating nootropic or anti-dementia drug candidates. It is also used in autonomic pharmacology studies to suppress parasympathetic tone, and in vestibular and antiemetic research.

References

1. Broadbent, N.J., et al. The role of the hippocampus in recognition memory. Behavioural Brain Research. Review article discussing cholinergic contributions to memory; scopolamine models referenced.
2. Caulfield, M.P. Muscarinic receptors — characterization, coupling and function. Pharmacology & Therapeutics. General reference for mAChR subtype pharmacology including M1 selectivity profiles.
3. Anagnostaras, S.G., et al. Selective cognitive dysfunction in acetylcholine M1 muscarinic receptor mutant mice. Nature Neuroscience. Supports the role of mAChR M1 in cognitive function.

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