Final answer:
In women, the blockage of dopamine transmission can lead to increased secretion of prolactin by the pituitary gland, causing hyperprolactinemia. Symptoms of this condition include amenorrhea, galactorrhea, and breast enlargement as prolactin levels are not properly regulated due to the disruption of the inhibitory effect of dopamine.
Step-by-step explanation:
Blockage of dopamine transmission can lead to increased pituitary secretions of prolactin. In women, this hyperprolactinemia can result in amenorrhea (the absence of menstruation), galactorrhea (unnecessary discharge of milk), and enlargement of the breasts. Typically, prolactin secretion is inhibited by prolactin-inhibiting hormone (PIH), which is actually the neurotransmitter dopamine, released from neurons in the hypothalamus. This hormonal regulation becomes disrupted when dopamine transmission is blocked, leading to the symptoms associated with hyperprolactinemia.
During pregnancy, prolactin levels naturally increase under the stimulation of prolactin-releasing hormone (PRH) from the hypothalamus to prepare for milk production. Post-pregnancy, prolactin-mediated milk production is regulated by a positive feedback loop involving the nipples, hypothalamus, and mammary glands. However, when dopamine transmission is blocked, prolactin levels can become excessively high, causing symptoms unrelated to pregnancy or breastfeeding.