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FUKUKO KIMURA, MASAZUMI KAWAKAMI, HIDEKI NAKANO, SAMUEL M. McCANN, Changes in Adenosine 3′,5′-Monophosphate and Guanosine 3′,5′-Monophosphate Concentrations in the Anterior Pituitary and Hypothalamus during the Rat Estrous Cycle and Effects of Administration of Sodium Pentobarbital in Proestrus, Endocrinology, Volume 106, Issue 2, 1 February 1980, Pages 631–635, https://doi.org/10.1210/endo-106-2-631
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Concentrations of cAMP and cGMP in the anterior pituitary and medial basal hypothalamus from female rats sacrificed by microwave irradiation at various stages of the estrous cycle were measured by RIA. Pituitary cAMP levels were the lowest at 1000 h on diestrous day 1, followed by higher levels that continued until 1600 h on proestrus. The level increased thereafter to reach a peak at 2200 h on proestrus. The levels on estrus were similar to those on diestrous day 1. Pituitary cGMP levels were low and almost steady from the diestrous days to the morning of proestrus, but in the afternoon of proestrus the level rose dramatically and peaked at 2200 h. The level returned to the proestrous morning level at 1000 h on estrus but increased again in the afternoon. The concentrations of both cAMP and cGMP in the hypothalamus started to rise in the late afternoon of diestrous day 2 and remained high through the day of proestrus. The levels were lower on the day of estrus. At 2200 h on proestrus, the cGMP level was elevated further to reach the maximum found during the cycle, while cAMP did not change. It was suggested that the concentrations of pituitary cyclic nucleotides increase in parallel with the increase of pituitary hormone output which takes place during proestrus, and that concentrations of hypothalamic cyclic nucleotides increase concomitant with the increase in the estrogen level in the blood which occurs from diestrous day 2 to proestrus. (Endocrinology106: 631, 1980)
