Bromocriptine (CAS 25614-03-3)

Bromocriptine is a semisynthetic ergot alkaloid.. This compound exhibits selective binding to and activation of postsynaptic dopamine D2-like receptors. These D2-like receptors are linked to inhibitory G-proteins, which consequently hinder adenylyl cyclase activity. By impeding the signal transduction mediated through cyclic adenosine monophosphate (cAMP), neurotransmission experiences an inhibitory effect. The dopamine D2 receptor, a 7-transmembrane G-protein coupled receptor connected to Gi proteins, plays a role in this process. Within lactotrophs, activation of the dopamine D2 receptor brings about a decline in intracellular cAMP levels through adenylyl cyclase inhibition. Consequently, this inhibits IP3-dependent release of calcium ions (Ca2+) from intracellular stores. Notably, the reduction in intracellular calcium levels can also occur via the inhibition of calcium influx through voltage-gated calcium channels, distinct from adenylyl cyclase inhibition. Moreover, dopamine receptor activation thwarts the phosphorylation of p42/p44 MAPK and diminishes phosphorylation of MAPK/ERK kinase. Inhibition of MAPK is believed to be facilitated by c-Raf and B-Raf-dependent suppression of MAPK/ERK kinase.