Effect of photoperiodic alterations on depression-like behavior and the brain serotonin system in mice genetically different in tryptophan hydroxylase 2 activity

Effect of Short Photoperiod on Behavior and Brain Plasticity in Mice Differing in Predisposition to Catalepsy: The Role of BDNF and Serotonin System

“…On the other hand, a short photoperiod did not affect the 5-HT metabolism in all of the studied brain structures of BL/6 mice. Our results are inconsistent with data that showed that C57BL/6 mice exposed to short-day conditions demonstrated a decreased 5-HT level in the amygdala [ 23 , 25 ] and midbrain [ 24 , 25 ], but not in the hypothalamus [ 23 ] and hippocampus [ 24 ]. These discrepancies may be caused by differences in the experimental designs and conditions.…”

“…It has been shown that C57BL/6J mice under short-day exposure demonstrated higher [ 33 ] or lower body weights [ 34 ], lower glucose tolerance, and altered plasma metabolomic profiles compared to the mice under long-day conditions [ 23 , 33 , 34 , 35 ]. In addition, C57BL/6J mice exposed for a month to short-day conditions showed increased sucrose intake and depressive-like immobility in the forced swim test (FST) [ 23 , 24 , 35 , 36 ]. The results of the present work are consistent with these data.…”

“…Discrepancies with other studies on FST results in BL/6 mice may be due to differences in the experimental design or conditions. For example, the experiments [ 24 , 36 ] were carried out on specific pathogen-free (SPF) conditions, which could significantly affect the behavioral results, since a short photoperiod may exert changes in immune processes [ 39 ].…”

“…Because mice are nocturnal, it was believed that these animals are not photoperiod sensitive and would not be suitable models for SAD. However, mice of the C57BL/6 strain exposed for 4 weeks to short-day conditions showed an increased sucrose intake, increased depressive-like immobility in the forced swim test, and a decreased 5-HT level in some brain structures [ 23 , 24 , 25 ]. These changes are consistent with the current understanding of the symptoms and mechanism of SAD.…”

Gut microbiota is associated with the effect of photoperiod on seasonal breeding in male Brandt’s voles (Lasiopodomys brandtii)

“…Many previous studies indicate that gut microbiota is closely associated with behavioral disorders in humans [ 77 ], but the effects photoperiod-exposed microbiota on aggressive behavior and daily rhythms in animals remain unclear. Serotonin (5-hydroxytryptamine; 5-HT), a precursor of melatonin (MT), is regulated by photoperiod and negatively correlated with aggressive behavior in rodents [ 78 , 79 ]. Intestinal enterochromaffin cells produce intestinal serotonin, which is stored and obtained by circulating platelets, participates in regulation of the membrane permeability in the brain, intestine, and other organs [ 80 ].…”