Biology of Reproduction, Vol 19, 439-446, Copyright © 1978 by Society for the Study of Reproduction

Dissociation Between Release of Luteinizing Hormone and Prolactin and Induction of Female Sexual Behavior in Normal and Androgenized Rats

¹ Neuroscience and Anatomy Departments and Brain Research institute University of California, Los Angeles, California 90024

In order to study the relationship between luteinizing hormone (LH) and prolactin (PRL) release and female sexual behavior, rats received an i.v. catheter on the day of estrus and were injected with oil or estradiol benzoate (EB; 2.5 µg/100 g) on the morning of diestrus I at 1000 h and with progesterone (P; 2 mg) on the next morning (1000 h of diestrus II). In experiment 1, blood samples for radioimmunoassay of LH and PRL were taken at 0900 h at at 1700 h of both days of diestrus. Lordosis behavior was tested at 2200 h of diestrus II. P facilitated LH and PRL release and lordosis behavior in EB-primed, but not oil-primed rats. In experiment 2, rats which received this same steroid regimen were bled every 30 min from 1000-1530 h or from 1430-1830 h of diestrus II. Additional unstressed rats given the same steroid treatment were tested for lordosis behavior at 1200, 1300, 1400 or 1500 h on diestrus II. Lordosis behavior was elevated by 1200 h, while augmented LH release did not occur until later in the afternoon (1430-1830 h). In order to document further this separation of LH and lordosis behavior, a third experiment was conducted using androgenized rats. Females were given either oil, 10 µg testosterone propionate (TP) on Day 5 of life to induce the delayed anovulation syndrome (DAS), or 30 µg TP on Day 2 to induce the full anovulation syndrome (FAS). These rats were cannulated and given the same steroid regimen as above and bled 4 times as in the first experiment. P facilitated LH release in both normal and cycling DAS rats, but not in persistent estrous DAS or FAS rats. However, P facilitated PRL secretion to the same level in all rats and augmented lordosis behavior in all groups except the FAS rats. These data indicate that in the normal animal, PRL and LH release and sexual behavior can all be advanced by steroid injections given during diestrus, but that LH release and lordosis behavior are dissociated temporally. Furthermore, in lightly androgenized rats exhibiting the DAS, lordosis behavior occurs even in the complete absence of facilitated LH release. It is clear that LH release and lordosis behavior are easily dissociated, suggesting that they are regulated at least in part by difference mechanisms.

Note:
ACKNOWLEDGMENTS The authors would like to express their gratitude for the invaluable technical assistance of James Shryne and David Whitmoyer and for the manuscript preparation by Loretta Kelley. We are also indebted to the NIAMDD Rat Pituitary Hormone Distribution Program for supplying the materials for the radioimmunoassay. Computing assistance was obtained from the Health Sciences Computing Facility, UCLA, supported by NIH Special Research Resources Grant RR-3.