Bromocriptine has the advantage of having a long duration of action, which can be demonstrated using an in vitro system. Anterior pituitary cells of a prolactinoma from a female patient were dispersed, placed in a perfusion apparatus, and perfused continuously. When the cells were exposed to dopamine, prolactin secretion was inhibited, but within ten minutes after the withdrawal of dopamine, prolactin secretion increased, becoming maximal after approximately fifteen minutes. Prolactin secretion was inhibited on exposure of the cells to bromocriptine. When the bromocriptine was withdrawn, however, prolactin secretion remained suppressed for over three hours. On re-exposure to dopamine, prolactin secretion was once more inhibited, recovering again on withdrawal of dopamine. These results are summarised graphically in Fig. 4.11.
