Hypothalamic Control of the Testis in the Ram

Adult Soay rams were maintained under an artificial lighting schedule which induced a seasonal cycle in testicular activity every 8 months. At 3 stages of the testis cycle (regressed, developing and active) the episodic nature of LH secretion was assessed from blood samples collected at frequent intervals. At the same time the LH release in response to 3 doses of LH‐RH (50, 250 and 1000 ng) was measured. The endogenous release of LH‐RH was then deduced from the episodic pattern of LH secretion using the dose response to synthetic LH‐RH as a standard. The result showed that in the ram LH‐RH secretion is episodic, and the hypothalamus regulates release by changing both the frequency and magnitude of the episodes of secretion.