Circadian rhythm in rat pineal serotonin and its modifications by estrous cycle and photoperiod

The influence of some pterins on the circadian rhythmicity of hydroxyindole-O-methyl transferase in the pineal gland of 42-day old male Wistar rats

“…It may therefore be expected that reduced neopterin is involved in this way in indole metabolism. The present results show that the effect of reduced neopterin seems to be important for all HIOMT activities and is not limited to the methylated product of 5-HTP, as was expected according to Lovenberg and Victor (1974 Quay (1963), was present at night.…”

Circadian rhythms of tonic immobility in the rat: Evidence of an endogenous mechanism

“…If these neurochemieals are indeed involved with the mechanism responsible for tonic immobility, then the daily changes in their concentration levels would be expected to correspond to the circadian cycle of TI in the present study. Serotonin levels in the rat pineal gland (Axelrod, 1974;Quay, 1963;Snyder , Zweig, Axelrod, & Fischer, 1965) and in the hypothalamus, frontal cortex, and brainstem (Quay, 1968) have cycles that are opposite in phase to the cycle of immobility duration in the present study. Pineal melatonin (Quay, 1964;Ralph, Mull, Lynch, & Hedlund, 1971), on the other hand, showed a circadian cycle that corresponds rather closely to the TI cycle in rats.…”

DIFFERENTIAL EFFECT OF BENSERAZIDE (Ro4‐4602) ON THE CONCENTRATION OF INDOLEAMINES IN RAT PINEAL AND HYPOTHALAMUS

“…(controls). Five or 6 animals from each group were injected and killed at different times after lights on as follows: injected at 3.0 h, killed at 4.0 h; injected at 3.0 and 5.5 h, killed at 6.0 h; injected at 3.0, 5.5 and 8.5 h, killed at 9.0 h; injected at 3.0, 5.5, 8.5 and 11.5 h, killed at 12.0 h; injected at 3.0,5.5, 8.5, 11.5 and 16.5 h, killed at 17.0 h; injected at 3.0, 5.5, 8.5, 11.5, 16.5 and 19.5 (Quay, 1963a;Wilkinson, Arendt, Bradtke & de Ziegler, 1977). During the dark phase animals were maintained and killed in dim red light.…”