Metabotropic receptors are G protein-coupled receptors (GPCRs) that undergo a conformational change upon ligand binding, activating G proteins and initiating downstream signaling cascades.

G proteins act as signal transducers, relaying signals from activated receptors to downstream effectors, such as enzymes, ion channels, or other signaling molecules.

Gs, Gi, and Gq are all common types of G proteins involved in signal transduction. Gs stimulates adenylyl cyclase, Gi inhibits adenylyl cyclase, and Gq activates phospholipase C.

Second messengers, such as cAMP, IP3, and DAG, amplify and diversify cellular responses by activating downstream effectors and initiating various signaling pathways.

Cyclic adenosine monophosphate (cAMP) is a common second messenger that mediates the effects of many hormones and neurotransmitters.

Protein kinases are enzymes that phosphorylate other proteins, altering their activity and function, and thereby regulating various cellular processes.

Protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein kinase (MAPK) are all examples of protein kinases involved in signal transduction.

Transcription factors are proteins that regulate gene expression by binding to specific DNA sequences and promoting or inhibiting transcription.

Nuclear factor kappa-B (NF-κB), signal transducer and activator of transcription (STAT), and activator protein-1 (AP-1) are all examples of transcription factors involved in signal transduction.

Nuclear receptors are transcription factors that bind to specific DNA sequences and directly activate transcription of target genes.

Estrogen receptor, glucocorticoid receptor, and thyroid hormone receptor are all examples of nuclear receptors.

Ion channels are membrane proteins that regulate the flow of ions across cell membranes, influencing membrane potential and cellular excitability.

Voltage-gated sodium channels, ligand-gated ion channels, and mechanosensitive ion channels are all examples of ion channels involved in signal transduction.

Drugs primarily exert their effects by binding to receptors and altering their activity, leading to changes in cellular signaling and physiological responses.

Morphine exerts its effects by binding to opioid receptors, altering their activity and reducing pain perception.