Peripubertal development of noradrenergic stimulation of luteinizing hormone-releasing hormone neurosecretion in vitro.
The effect of age on norepinephrine (NE) stimulation of luteinizing hormone-releasing hormone (LH-RH) secretion from preoptic area-mediobasal hypothalamic (POA-MBH) explants was examined in the present study. Explants were obtained from juvenile (9-day-old), prepubertal (29-day-old) and adult female rats. Following decapitation and surgical isolation, POA-MBH explants were individually perifused with culture medium which was collected for radioimmunoassay of LH-RH. Explants were exposed to two pulses of medium containing NE (5 x 10(-4) M, peak concentration) and a terminal pulse of medium containing KCl (45 mM, peak concentration) for assessment of viability. POA-MBH explants obtained from prepubertal female rats exhibited increased LH-RH release in response to the two pulses of NE and subsequent KCl pulse (P less than 0.05). NE was without effect in stimulating LH-RH neurosecretion from POA-MBH explants obtained from 9-day-old female rats although these explants were responsive to KCl (P less than 0.01). Two-day pretreatment of 9-day-old, and prepubertal rats with estradiol benzoate (EB) did not alter the LH-RH response to this dose of NE or KCl (no group or interaction effects) in prepubertal female rat explants and did not render the explants from 9-day-old rats responsive to NE. Furthermore, NE was equally effective in stimulating LH-RH release from explants obtained from estradiol-treated or control ovariectomized adult rats. These observations demonstrate a peripubertal activation of the stimulatory effect of NE on LH-RH release from POA-MBH explants in vitro. Although these data also suggest that estrogen is not obligatory for NE stimulation of LH-RH release from POA-MBH explants, further investigation is required to determine the developmental time course and estrogen dependency of the noradrenergic stimulation of LH-RH neurosecretion and to evaluate whether estrogen alters the sensitivity of POA-MBH explants to lower concentrations of NE as has been previously reported for median eminence fragments.
Clough
R W
RW
Department of Neurobiology, University of Rochester School of Medicine and Dentistry, NY 14642.
Hoffman
G E
GE
Sladek
C D
CD
D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000187:drug effects / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D007700:Kinetics; D009638:Norepinephrine / Q000494:pharmacology*; D009924:Organ Culture Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D011301:Preoptic Area / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation
D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D011189:Potassium Chloride; D009638:Norepinephrine