BLOOD PRESSURE, PLASMA AND PITUITARY PROLACTIN RESPONSES TO BROMOCRIPTINE IN NEW ZEALAND GENETICALLY HYPERTENSIVE AND NORMOTENSIVE RATS

1. The effects on blood pressure (BP), plasma and pituitary prolactin (PRL) of a 13 day intraperitoneal infusion of bromocriptine (BRC) delivered by osmotic minipump were investigated in genetically hypertensive rats (GHR) and their normotensive (NT) controls. 2. In the GHR, the mean BP in the BRC-treated group over the 13 day period of study was significantly lower than in the vehicle-treated group. In the NT rats, the mean BP in the BRC-treated group over the 13 day period was also significantly lower than in the vehicle-treated group. 3. Mean plasma PRL concentration in the GHR and NT rats were comparable. In the GHR, the mean plasma PRL concentration taken on day 13 was significantly lower in the BRC-treated group than in the vehicle-treated group. In the NT rats, the mean plasma PRL concentration taken on day 13 in the BRC-treated group was, however, not significantly different from that in the vehicle-treated group. 4. The mean pituitary PRL content was not significantly different in the GH and NT rats. There was a greater suppression of pituitary PRL content in the BRC-treated GHR than in the BRC-treated NT rats compared with their respective vehicle-treated groups. 5. The results raise the possibility that PRL may have an indirect role in the pathogenesis of the hypertension of the GHR.