Sex matters: females in proestrus show greater diazepam anxiolysis and brain‐derived neurotrophin factor‐ and parvalbumin‐positive neurons than males

Abstract

In humans and animal models, sex differences are reported for anxiety-like behavior and response to anxiogenic stimuli. In the current work, we studied anxiety-like behavior and response to the prototypical anti-anxiety drug, diazepam. We used 6th generation outbred lines of adult Long Evans rats with high and low anxiety-like behavior phenotypes to investigate the impact of proestrus on the baseline and diazepam-induced behavior. At three doses of diazepam (0, 0.1, and 1.0 mg/kg, i.p.), we measured anxiogenic responses on the elevated plus maze of adult male and female rats. We assessed parvalbumin and brain-derived neurotrophin protein levels in forebrain and limbic structures implicated in anxiety/stress using immunohistochemistry. At baseline, we saw significant differences between anxiety lines, with high anxiety lines displaying less time on the open arms of the elevated plus maze, and less open arm entries, regardless of sex. During proestrus, high anxiety females showed less anxiety-like behavior at 0.1 mg/kg, while low anxiety females displayed less anxiety-like behavior at 0.1 and 1.0 doses, relative to males. Brain-derived neurotrophin protein was elevated in females in the medial prefrontal cortex and central amygdala, while parvalbumin-immunoreactive cells were greater in males in the medial prefrontal cortex. Parvalbumin-positive cells in high anxiety females were higher in CA2 and dentate gyrus relative to males from the same line. In sum, when tested in proestrus, females showed greater anxiolytic effects of diazepam relative to males, and this correlated with increases in neurotrophin and parvalbumin neuron density in corticolimbic structures.

Crybb2 Mutations Consistently Affect Schizophrenia Endophenotypes in Mice

“…At least for the dorsal hippocampus, this seems to be in line with a previous report that demonstrates higher levels of parvalbumin protein expression in male than in female C57BL/6 mice in the dorsal, but not in the ventral hippocampus [57]. However, in Long Evans rats recently, a higher parvalbumin protein level was reported in the dentate gyrus of females during proestrus compared to males [58]. The discrepancies might be due to species or methodological differences between the studies.…”

GABAA/Benzodiazepine Receptor Complex in the Dorsal Hippocampus Mediates the Effects of Chrysin on Anxiety-Like Behaviour in Female Rats

“…Increases in the number of entries into the open arms and time spent on the open arms were brought about by the microinjection of 0.5 μg of chrysin and allopregnanolone in the dorsal hippocampus in dioestrus rats. This behavioural change suggests an anxiolytic-like effect that is similar to that of anxiolytic drugs such as benzodiazepines and their derivatives ( Rezvanfard et al, 2009 ; Ravenelle et al, 2018 ; Rombolà et al, 2019 , 2020 ).…”

“…At the preclinical level, anxiety-like behaviour is higher during metoestrus-dioestrus, characterised by low concentrations of steroid hormones than proestrus-oestrus which, in contrast, presents high hormonal concentrations ( Marcondes et al, 2001 ). This naturally occurring anxiety-like behaviour prompted the evaluation of substances that relieve anxiety associated with metestrus-dioestrus ( Ravenelle et al, 2018 ; García-Ríos et al, 2019 ; Rodríguez-Landa et al, 2021 ), which is a physiological state similar to the premenstrual period in women ( Lovick, 2008 ). In this way, some flavonoids exert anxiolytic-like effects in rodents.…”