Stimulatory role of prolactin on the development of tuberoinfundibular dopaminergic neurones in prepubertal female rats: studies with cysteamine and somatostatin.
Cysteamine, a potent depletor of prolactin and somatostatin, was used to determine the role of prolactin and somatostatin in the control of central dopamine neurones in prepubertal rats. Cysteamine (100 mg/kg, i.p., twice daily) was injected for 7, 14 or 21 days in 28-day-old Sprague-Dawley female rats in one study and for 3 days in 35-day-old rats in another. In control rats, the 3, 4-dihydroxyphenylacetic acid (DOPAC) levels in the median eminence increased threefold from day 35 to day 49, and serum prolactin concentration increased about 50%. Cysteamine lowered serum prolactin concentrations to 20%, and median eminence DOPAC and dopamine levels to 32-50% of control levels in both studies. The DOPAC levels in the nucleus accumbens and striatum were also lowered, while both DOPAC and dopamine in the paraventricular nucleus and periventricular nucleus (A14) were increased by cysteamine. A single injection of rat prolactin (0.01, 0.1 or 1 mg/kg) significantly increased DOPAC or DOPA levels in the median eminence, nucleus accumbens and striatum, but not in the paraventricular nucleus or A14 at 14 h later in 28-day old female rats or in 40-day-old rats pretreated with cysteamine. In contrast, central injection of somatostatin dose (0.001-1 microg/rat) and time (30-90 min) dependently decreased the DOPAC levels in the median eminence, paraventricular nucleus and A14 and increased those in the nucleus accumbens and striatum of adult female rats. These results indicate that serum prolactin is important for the maturation and maintenance of dopamine systems in the median eminence, nucleus accumbens and striatum, while somatostatin exhibits inhibitory and stimulatory effects on hypothalamic and midbrain dopamine systems, respectively.
Shieh
K R
KR
Department of Physiology, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan.
Pan
J T
JT
D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D000367:Age Factors; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D003342:Corpus Striatum / Q000737:chemistry / Q000166:cytology; D003543:Cysteamine / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006728:Hormones / Q000494:pharmacology*; D007031:Hypothalamus / Q000737:chemistry / Q000166:cytology; D008473:Median Eminence / Q000737:chemistry / Q000166:cytology; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000737:chemistry / Q000166:cytology; D010052:Ovariectomy; D010286:Paraventricular Hypothalamic Nucleus / Q000737:chemistry / Q000166:cytology; D010902:Pituitary Gland / Q000737:chemistry / Q000166:cytology; D011388:Prolactin / Q000502:physiology*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012741:Sexual Maturation / Q000502:physiology*; D013004:Somatostatin / Q000494:pharmacology*; D013268:Stimulation, Chemical
D004967:Estrogens; D006728:Hormones; D011837:Radiation-Protective Agents; D015102:3,4-Dihydroxyphenylacetic Acid; D013004:Somatostatin; D003543:Cysteamine; D011388:Prolactin; D004298:Dopamine