Central adrenergic activity in the mediobasal hypothalamus is temporally related to surge outputs of gonadotrophins in oestrogen-stimulated infant female rats.
In the mediobasal hypothalamus (MBH) of pro-oestrous rats or acutely ovariectomized oestrogen-treated adults a marked but short-lived increase in adrenergic activity occurs at 16.00 h, 2 h before the oestrogen-dependent surge of gonadotrophins at 18.00 h. In this study oestrogen-stimulated (noon on day 1) 22-day-old female rats were used which are known to produce surge levels of prolactin at 18.00 h on day 2 and surges of both prolactin and LH at 18.00 h on day 3; although similar treatment of 18-day-old animals or oil-treated 22-day-old rats failed to produce these effects. Radioenzymatic assays of adrenaline concentrations and of the activity of its synthesizing enzyme (phenylethanolamine-N-methyl transferase; PNMT, EC 2.1.1.28) in the MBH of oestrogen-treated 22-day-old rats showed significant (P less than 0.05-0.01) increases in both parameters at 16.00 h (i.e. 2 h before surge levels of gonadotrophins) on days 2 and 3 when compared with other times of day. Such effects were not seen in oil-treated 22-day-old animals or in oestrogen-treated 16-day-old rats. Noradrenaline and dopamine concentrations in the MBH of oestrogen-treated 22-day-old rats remained at baseline levels on days 2 and 3 with the exception of noradrenaline at 17.00 h on day 3 when levels appeared higher (P less than 0.05) than at either 15.00 or 16.00 h.(ABSTRACT TRUNCATED AT 250 WORDS)
E M
EM
Clement
P C
PC
MacKinnon
R
R
Sheaves
D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D004837:Epinephrine / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism; D010052:Ovariectomy; D010625:Phenylethanolamine N-Methyltransferase / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D002395:Catecholamines; D006065:Gonadotropins, Pituitary; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone; D010625:Phenylethanolamine N-Methyltransferase; D004837:Epinephrine