Sex differences in diazepam effects and parvalbumin-positive GABA neurons in trait anxiety Long Evans rats

Abstract

In clinical populations, prevalence rates for a number of anxiety disorders differ between males and females and gonadal hormones are thought to contribute to these differences. While these hormones have been shown to modulate the anxiolytic effects of the benzodiazepine agonist diazepam in some models, findings are inconsistent. Here, we tested for sex differences in response to anxiogenic stimuli following a 30-min diazepam (1.0 mg/kg) pre-treatment in male and female rats showing high (HAn) and low (LAn) anxiety-like behavior on the elevated plus maze. Acute diazepam administration resulted in decreased anxiety-like behavior only in HAn males as demonstrated by a significant increase in percent open arm time in the elevated plus maze (EPM). Immunohistochemical analysis for parvalbumin (PV; a calcium-binding protein that selectively stains GABAergic neurons) in central amygdala (CeA), caudate putamen (CPu) and the hippocampus indicated the number of GABAergic interneurons in these areas differed across sex and anxiety trait. In the CPu, females had significantly more PV-immunoreactive (IR) cells than males, and LAn females had greater PV-IR neurons than HAn females. In the CeA, males displayed an increased number of PV-IR neurons compared to females, with no differences found between LAn and HAn. Further, trait differences were evident in the CA2 region of the hippocampus, regardless of sex. Taken together, these data suggest that gonadal hormones and trait anxiety may influence the sensitivity to the anti-anxiety effects of diazepam and these differences may be due in part to the distribution of GABA-containing interneurons.

The densities of calbindin and parvalbumin, but not calretinin neurons, are sexually dimorphic in the amygdala of the guinea pig

“…The present results demonstrate that the densities of PVþ neurons are also sexually dimorphic in the amygdala of the guinea pig as they are also in several other brain regions of the rat (Stefanova et al, 1997b;Ravenelle et al, 2014). The pattern of sexual dimorphism in the case of PVþ neurons was in the amygdala quite similar to that found for CBþ cells.…”

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

“…This study was designed to extend our previous findings showing greater diazepam effects on EPM in males displaying high anxiety‐like behavior compared to females, and GABA neuron density positively correlating with low anxiety‐like behavior. While we did not show similar diazepam effects on females in that work, we did not isolate the stage of estrous (Ravenelle et al ., ). It is probable that given the variable stages of estrous for the females, there is greater variability in the female group.…”

“…Anti-anxiety drugs work, at least in part, by acting on PV-expressing GABA interneurons in the basolateral amygdala (Hale et al, 2010). Increases in PV-positive neurons have been demonstrated in the basolateral amygdala of rats reared in an enriched environment, and these changes are associated with reduced anxietylike behavior (Urakawa et al, 2013;Ravenelle et al, 2014).…”

Parvalbumin Interneurons of Central Amygdala Regulate the Negative Affective States and the Expression of Corticotrophin-Releasing Hormone During Morphine Withdrawal

“…It has been reported that few PV + interneurons are shown in the CeA by immunoreactive methods in rats (Zahm et al, 2003; Ravenelle et al, 2014). The immunohistochemical images of Zahm et al (2003) show a small quantity cell body of PV + interneurons in the CeA, which is consistent with our immunofluorescence results using PV antibody.…”

“…Although PV + interneurons are not the biggest interneuron population in the CeA, their function in the CeA has been indicated to be significantly related to anxiety-like behavior (Ravenelle et al, 2014). However, whether the plasticity of PV + interneurons of CeA can be modulated during drug withdrawal, and their function and neurophysiological mechanism in regulating negative affective symptoms during withdrawal, are largely unknown.…”