Studies on the accessibility of prolactin and growth hormone to brain: effect of opiate agonists on hormone levels in serial, simultaneous plasma and cerebrospinal fluid samples in the rhesus monkey.
The accessibility of prolactin and growth hormone to the cerebrospinal fluid (CSF) was investigated in rhesus monkeys fitted with reservoirs connected to catheters placed in the fourth ventricle. Simultaneous blood and CSF samples were collected after opiate agonists. There was a brisk, marked rise in plasma prolactin following i.v. morphine sulphate which was followed by a slower, lesser rise in CSF prolactin. After i.v. D-Ala2,MePhe4,Met-O-(ol)-enkephalin (DAMME, FK 33-824, Sandoz) two animals responded similarly but the third showed a much smaller plasma and absent CSF response. Growth hormone showed inconsistent plasma patterns after morphine but a late rise following DAMME; however, CSF growth hormone did not change. Infusion of exogenous human prolactin produced plasma and CSF prolactin levels of similar magnitude and time-course as following opiate agonists. Infusions of larger amounts of purified human growth hormone greatly elevated plasma levels but only led to modest increases in CSF growth hormone. It is concluded that prolactin has relatively ready access to CSF, especially in comparison to growth hormone. The possible significance and mechanisms are discussed.
D000818:Animals; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000134:cerebrospinal fluid*; D007700:Kinetics; D008253:Macaca mulatta; D009020:Morphine / Q000494:pharmacology; D011388:Prolactin / Q000097:blood / Q000134:cerebrospinal fluid*
D004745:Enkephalins; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D009020:Morphine; D011388:Prolactin; D013006:Growth Hormone