EFFECT OF CORTICOTROPIN-RELEASING FACTOR (CRF) INJECTED INTO THE MEDIAN-EMINENCE ON LH-SECRETION IN MALE-RATS

We determined the dose-response relationship and examined the time-rel ated effect of CRF (corticotropin releasing factor) injected directly into the Median Eminence (ME) on LH secretion in conscious intact and castrated male rats. Doses of 0.25, 0.75, 1, and 1.5 nmol CRF dissolve d in 1 mu l of saline (or saline only in the controls) were injected i nto the ME and blood samples collected 30, 60, 90, and 120 min postinj ection to determine by RIA serum LH. CRF at doses of 0.75, 1 and 1.5 n mol significantly decreased serum LH in castrated and intact animals. The lower dose of CRF did not decrease LH in the two groups studied. T he results suggest that in males as in females, CRF inhibits by itself LH secretion, at least in part, by a central action in the ME; the in hibitory effect of CRF on LH is similar in castrated and intact males; the dose of 0.25 nmoles of CRF was ineffective in decreasing LH and f inally that CRF at ME levels may participate in a variety of stress-re lated responses, including reproduction inhibition, through LH suppres sion.