Day/night serotonin levels in the pineal gland of male BALB/c mice with melatonin deficiency

Abstract

Studies from another laboratory have shown that several strains of laboratory mice have a genetic defect for melatonin synthesis. In non-deficient species, melatonin synthesis undergoes a typical, \g=b\-adrenergically regulated day/night rhythm with low melatonin levels during daytime and high levels at night, the precursor serotonin showing an inverse behaviour. This study examines whether a day/night rhythm of pineal serotonin levels exists in melatonin-deficient male BALB/c mice. Mice kept under a lighting schedule of 12 h light (lights on at 07.00 h) and 12 h dark were killed at 13.00 and 01.00 h, respectively. Serotonin amounted to 12-15 ng/pineal and did not show regular day/night differences. Administration of the \g=b\-adrenergic agonist, isoproterenol, which is known to affect melatonin synthesis in a number of species, was without effect on pineal serotonin levels. Melatonin and two of the melatonin-forming enzymes, serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) were below the detection limit in the pineal. It is concluded that in melatonin-deficient BALB/c mice, pineal serotonin synthesis is apparently intact. In BALB/c mice, serotonin synthesis and release do not appear to be directly or indirectly regulated by \g=b\-adrenergic mechanisms.

Immunocytochemical demonstration of day/night changes of clock gene protein levels in the murine adrenal gland: differences between melatonin‐proficient (C3H) and melatonin‐deficient (C57BL) mice

“…In the the adrenal cortex of C57BL mice the levels of PER1, CRY2 and BMAL1 did not change significantly between the time points investigated and overall, they were lower than in the adrenal medulla. These observations are in accord with the results of Bittman et al [12] who showed that Per1 mRNA levels were lower in the adrenal cortex than in the adrenal medulla of BALB/c mice, another melatonin-deficient strain [36]. Clock gene protein levels displayed significant changes over time in the adrenal medulla of C57BL which, in principle, resembled the changes in the adrenal medulla of C3H mice.…”

Circadian rhythm of melatonin, corticosterone and phagocytosis: effect of stress

“…For this strain, there are apparent major contradictions in experimental results concerning the pineal production of melatonin due to the possible absence of genetic factors essential for melatonin synthesis in inbred mice. Thus, while a number of authors report no detectable melatonin in the pineal gland of these animals [Ebihara et al, 1986[Ebihara et al, , 1987Vollrath et al, 1988;Goto et al, 1989], Conti and Maestroni [1996] and Vivien-Roels et al [1998] have recently demonstrated the presence of a short-term peak of melatonin in the middle of the dark period. For this reason, we performed a detailed study with short time intervals during the night, to obtain values for serum melatonin levels in inbred BALB/c mice.…”

Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism

“…When the possible causes of the impaired melatonin production in mice were examined, it was found that C57Bl, AKR/J, and BALB/c mice had neither NAT nor HIOMT activity in the pineal gland, whereas another strain (NZB/BLNJ) had NAT but no HIOMT activity (7). The lack of NAT activity in the pineal gland was later confirmed in BALB/c mice (34). In the case of C57Bl/6J mice, it was found that a point mutation in the NAT gene results in a truncated protein that has little or no enzyme activity (30), whereas different mutations are present in BALB/c and 129/Sv strains (30).…”