Final answer:
Beta adrenergic blockers and anticholinergics can be used to treat decreased salivary flow before surgery by blocking β-receptors and acetylcholine receptors respectively.
Step-by-step explanation:
Beta adrenergic blockers and anticholinergics can be used to treat decreased salivary flow before surgery. Beta adrenergic blockers, such as propanolol and metoprolol, block the β-receptors associated with vasoconstriction and cardioacceleration. By preventing these effects, they can help reduce salivary flow. Anticholinergic drugs, like atropine, act as antagonists to muscarinic acetylcholine receptors, blocking the effects of excess acetylcholine and reducing salivary gland secretions.