Rhythmic pineal-hypophyseal-adrenal intermodulations ex vivo.

To assess circadian and circaseptan rhythmic intermodulation, female mice, kept on regimens of 12 hr light (L) alternating with 12 hr of darkness (D) (LD 12:12) were sampled for 1-13 days at six circadian stages. Pineals were removed and homogenized with 0.9% NaCl. Adenohypophyses were bisected and incubated in Krebs-Ringer buffer (KRb) and/or with 10(-7) M melatonin (Mt). Adrenals were bisected and incubated with KRb, with 10(-7) M Mt, with 0.05 IU of ACTH 1-17 (Sy; Hoechst, Italy), or with Sy + 0.025 ml of the aqueous pineal homogenate (APH). ACTH and prolactin (PRL) in adenohypophysis incubation fluid were determined by radioimmunoassay (RIA), and corticosterone in adrenal incubation fluid was determined by RIA or by a fluorometric method. By this chronobiologic approach, time series were collected systematically in the search for predictable variability. Once these series reveal an algorithmically formulatable pattern, with a waveform validated by inferential statistical means, they are graded in terms of complexity as alpha, beta, gamma, and delta rhythms. Spontaneously (alpha-) rhythmic along the 24-h scale is the corticosterone produced by bisected adrenal glands incubated with KRb only, and the Mt content of the APH, in keeping with earlier work. Reactively (beta-) rhythmic is the response, again along the 24-hr scale, of the adrenal to Sy or Mt and the response of the anterior pituitary to Mt at different circadian times. Modulatory (gamma and delta) rhythms characterize the Mt effect on the (beta-rhythmic) adrenal stimulation by Sy. Chronomodulations thus emerge as more or less complete sequences of a decrease, no effect and/or increase; or, rather, as an attenuation, no effect and/or amplification by the pineal, of the pituitary effect upon the adrenal. Linear least-squares rhythmometry, mostly single cosinors, describes and quantifies circadian (alpha, beta, and gamma) and infradian (delta) rhythms in the original series and in the differences in responses [beta - alpha] and [gamma - beta] (P less than 0.001 in each case). These spontaneous alpha, response beta, modulatory gamma, and frequency-divided delta rhythms reveal a collateral neuroendocrine hierarchy, characterized by the pineal feedsideward phenomenon, as a feature of interactions recurring with circadian and infradian frequencies.