Which receptors are known to increase intracellular Ca2+? (Choose 2)

Alpha 1 and muscarinic receptors are known to increase intracellular calcium levels. Alpha 1 receptors, which are a type of adrenergic receptor, primarily act through a G protein-coupled mechanism that activates phospholipase C. This leads to the production of inositol triphosphate (IP3) and diacylglycerol (DAG), ultimately resulting in the release of calcium from the endoplasmic reticulum and an increase in intracellular calcium concentration.

Muscarinic receptors, particularly M1, M3, and M5 subtypes, also utilize a similar pathway by activating phospholipase C upon binding to acetylcholine. The subsequent increase in IP3 facilitates calcium release from the endoplasmic reticulum, further contributing to the rise in intracellular calcium levels.

In summary, both alpha 1 and muscarinic receptors are effective in stimulating pathways that lead to increased calcium influx or release, making the response associated with these receptors key in various physiological processes.