Presence of a Distinct 24‐Hour Melatonin Rhythm in the Ventricular Cerebrospinal Fluid of the Goat

Abstract

Melatonin profiles in the cerebrospinal fluid (CSF) of conscious goats were examined under long-day (16L:8D) and short-day (8L:16D) environments. CSF melatonin, collected from the lateral ventricle, showed distinct 24 h rhythms with high concentrations being restricted to the dark phase, which averaged 1,320.6 pg/ml under 16L:8D and 660.6 pg/ml under 8L:16D. On the contrary, the nocturnal rise in CSF melatonin was totally absent in the pineal sympathetically denervated animals. Night interruption by 1 h lighting (about 400 lux at the height of goat's head) resulted in an abrupt decline of CSF melatonin to the basal level within 30 min and immediate recovery to the previous high level after reestablishment of the dark phase. The CSF/plasma ratio was 10.8-18.4 during the dark phase and 1.7-1.8 during the light phase. CSF and plasma melatonin levels were also examined after exogenous melatonin given either peripherally or intraventricularly. Continuous subcutaneous infusion of melatonin (5 micrograms/h) maintained melatonin levels in the plasma about 3 times higher than that in the CSF during its application. On the other hand, an intraventricular injection of 2 micrograms melatonin elevated plasma melatonin by 100 pg/ml within 1 min. These results indicate that turnover of CSF melatonin is fairly rapid and favor a hypothesis for direct access of pineal melatonin to the brain ventricular system in the goat.

Effect of Melatonin Injected into the Third Ventricle on Growth Hormone Secretion in Holstein Steers

“…The endogenous MEL, secreted from the pineal gland, is detected not only in the blood but also in the CSF in several species, such as non-human primates [22], sheep [25], goats [11] and cattle [9]. The existence of MEL in the CSF is very important, because MEL from the pineal gland is supposed to enter the CSF through the pineal recess [28], and would reach the peri-3V area, especially the hypothalamus, the presumable target site of MEL controlling the reproductive axis in sheep [16,18].…”

“…The MEL secretion has a distinct nocturnal rise in cattle [5,9] likewise in other species [11,13,22]. It is well known that GH secretion also has a nocturnal increment in humans [7].…”

Fibre growth of cashmere-bearing goats given melatonin in late autumn and winter

“…The role of the pineal gland in controlling seasonal physiological changes in mammals is well recognised. This gland produces the indoleamine melatonin in a rhythmic manner (Kanematsu et al 1989) such that plasma melatonin concentrations are greatest during hours of darkness and lowest during the day (Rollag & Niswender 1976;Kennaway et al 1977;Almeida & Lincoln 1984;Maeda etal. 1984;.…”

Melatonin: reducing the toxicity and increasing the efficacy of drugs

“…In the bile, for example, levels range up to 4000 pg mL 1 (Tan et al 1999a) compared with maximal blood levels of around 250 pg mL 1 (Reiter 1991 ;Arendt 1988Arendt , 1993a. Likewise, within the cerebrospinal¯uid, recent studies have shown that melatonin concentrations can be very high, up to roughly 90 nm (Kanematsu et al 1989 ;Skinner & Malpaux 2000 ;Tricoice et al 2001). Within some cells and subcellular compartments also, melatonin levels exceed those in the blood many fold (MenendezPelaez & Reiter 1993 ; Menendez-Pelaez et al 1993 ; Martin et al 2000b).…”