Destruction of the Dorsal Anterior Hypothalamic Region Suppresses Pulsatile Release of Follicle Stimulating Hormone but Not Luteinizing Hormone

Abstract

The region of the paraventricular nucleus-dorsal anterior hypothalamic area (PVN-DAHA) previously was implicated in the control of tonic FSH secretion. However, the role that this hypothalamic area plays in governing pulsatile FSH release is unknown. To examine this question, radiofrequency (RF) lesions were produced bilaterally in the PVN-DAHA of adult female rats which had been ovariectomized for 4 weeks. Control animals received sham lesions. After a recovery period of 1 week, all rats were fitted with jugular cannulae. The next day sequential blood samples were withdrawn from conscious, undisturbed rats at 10-min intervals for 3 h. Control animals displayed secretory peaks of FSH in plasma with a frequency of 4.0 +/- 0.44/3-hour period (or 1 peak/40-50 min). LH in plasma pulsed at a frequency of 5.8 +/- 0.49 peaks/3 h (or 1 peak/20-30 min). Both of these control values were in agreement with previous studies. RF lesion of the PVN-DAHA reduced FSH peak frequency to 1.2 +/- 0.37 peaks/3 h (p less than 0.001) and also significantly suppressed the mean peak height and trough values for FSH (p less than 0.001). In contrast, none of these parameters for pulsatile LH secretion was altered by the lesion. Immediately after the 3-hour sampling period, synthetic LHRH (50 ng/100 g BW) was infused intravenously into rats and blood samples withdrawn 10 and 40 min later to determine whether the responsiveness of the pituitary gland had changed as a result of the lesion.(ABSTRACT TRUNCATED AT 250 WORDS)