Co-localization of midbrain projections, progestin receptors, and mating-induced fos in the hypothalamic ventromedial nucleus of the female rat

ABSTRACT By using the synthetic progestin promegestone (R5020), the location and characteristics of progestin receptors in the thymic cytosols from immature ovariectomized oestrogen-treated rats were determined. Tritiated promegestone bound to the cytosol with high affinity (dissociation constant (Kd) = 2·0± 0·3 nmol/l; promegestone > progesterone > oestradiol > corticosterone ≃testosterone) and low capacity (number of binding sites (Bmax) = 143·0 ±13·5fmol/mg protein). These values were appropriate for progestin receptors. However, an extremely high dose of dexamethasone (10 μmol/l; 1000-fold excess over [3H]promegestone) slightly inhibited the specific binding. Progestin receptors were predominantly located in the reticuloepithelial (RE)-cell fraction, with few in the thymocyte T-cell fraction. The receptor level was raised (24·9 ± 11·3 (s.e.m.) to 143·0 ± 13·5 fmol/mg protein) with increased doses of oestrogen (0–30 μg) administered in vivo. Using sucrose density gradient ultra-centrifugation it was found that the thymic progestin receptor had a sedimentation coefficient of 9 S under low-salt conditions. These results clearly suggest that the thymus of the immature female rat contains a specific progestin receptor which is mainly located in the RE cells. J. Endocr. (1985) 107, 223–229

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The hypothalamic ventromedial nucleus sends a met-enkephalin projection to the preoptic area's periventricular zone in the female rat

Molecular Brain Research ◽

10.1016/0169-328x(95)00222-e ◽

1996 ◽

Vol 36 (2) ◽

pp. 201-210 ◽

Cited By ~ 14

Author(s):

G.E. Hoffman ◽

J. Dohanics ◽

R.E. Watson ◽

S.J. Wiegand

Keyword(s):

Ventromedial Nucleus ◽

Female Rat

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Ligand-independent activation of progestin receptors: relevance for female sexual behaviour

Reproduction ◽

10.1530/rep.0.1220847 ◽

2001 ◽

pp. 847-855 ◽

Cited By ~ 25

Author(s):

AP Auger

Keyword(s):

Ligand Binding ◽

Rat Brain ◽

Sexual Behaviour ◽

Steroid Receptors ◽

Neuronal Response ◽

Female Rat ◽

Progestin Receptors ◽

Dependent Processes

Traditionally, steroid receptors were believed to be activated only by ligand binding; however, recent studies indicate that steroid receptors can also be activated by mechanisms that do not require ligand, referred to as ligand-independent activation. Specifically, progestin receptors can be activated in vitro and in vivo after treatment with neurotransmitters, such as dopamine, in the absence of progesterone. Furthermore, mating-related stimuli can also lead to ligand-independent activation of progestin receptors in female rat brain. This finding indicates that environmental stimuli can influence steroid receptor-dependent processes in the absence of circulating hormone. This review focuses on studies indicating that progestin receptors can be activated in the absence of progesterone to influence neuronal response and sexual behaviour in rodents.

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