Maturation of the oestrogen-dependent LH-stimulating activity of the mediocortical amygdala in female rats.

Immature female Wistar rats were unilaterally implanted with oestradiol benzoate (OB) into the anterior (AMAN) or posterior part (PMAN) of the medial amygdaloid nucleus, or into the central part of the cortical amygdaloid nucleus (CCAN) at different ages. Autopsy was performed 56h after implantation, and the LH concentration in the plasma was estimated by radioimmunoassay. A significant rise of the LH level resulted from implantation of OB: into the PMAN at 21, 26 and 32 days of age, into the AMAN at 32 and into the CCAN at 26 and 36, but not at 32 days of age. The conclusion was drawn that the medial amygdaloid nucleus may be involved in the maturation of the positive oestrogen feedback mechanism. The prepuberal change in the oestrogen-dependent LH-controlling activity of the cortical amygdaloid nucleus indicates that this nucleus may participate in the control of the onset of puberty.