The effects of estradiol on avoidance learning in ovariectomized adult rats

Abstract

The present study examined the effects of ovariectomy and subsequent estradiol replacement on learning in young adult rats using a set of instrumental avoidance paradigms differing in the nature and extent of prior experience in the learning context. Thus, one group of animals was placed directly into avoidance learning (AV). A second group was trained on an appetitive task first, and then transferred into the aversive context (AP-AV). The third group was exposed to the training context without any specific appetitive response requirement, and then required to learn an active avoidance response (Context-AV). We found that estradiol (OVX+E) impaired avoidance acquisition in all cases relative ovariectomized controls (OVX). In contrast, while avoidance learning is improved following appetitive training or context exposure in both OVX+E and OVX animals, the OVX+E animals profit to a greater extent from the appetitive or context experience than do the OVX controls. We suggest that this difference may be due to enhanced attentional processes or improved hippocampal processing of contextual factors. Thus, estradiol negatively influences simple associative avoidance learning in ovariectomized rats, but appears to promote positive transfer.

The cortical response to sensory deprivation in adult rats is affected by gonadectomy

“…Adult female Long-Evans Hooded rats ( n = 12) were ovariectomized (OVX) using methods previously employed in our laboratory (Goodman et al 2004). Briefly, female rats were anesthetized with isoflurane gas, and 2 cm incisions were made bilaterally at the dorsal/ventral midsection just posterior to the ribcage, extending through the muscle wall.…”

Estradiol shifts interactions between the infralimbic cortex and central amygdala to enhance fear extinction memory in female rats

“…Estradiol influences many types of learning and memory processes (Luine et al, 1998; Goodman et al, 2004; Leuner et al, 2004; Inagaki et al, 2010; Cover et al, 2014), and studies examining estradiol’s effects on neurogenesis, dendritic branching, and long-term potentiation have demonstrated that it can alter brain structure and function as well (Galvin and Ninan, 2014; Mahmoud et al, 2016; Srivastava et al, 2013). Given the higher prevalence of fear and anxiety disorders in women compared to men, a better understanding of how estradiol can affect the neural substrates and mechanisms that control fear responses is necessary.…”

Reproductive experience modifies the effects of estrogen receptor alpha activity on anxiety-like behavior and corticotropin releasing hormone mRNA expression

“…These dramatic fluctuations in circulating estrogens likely affect neural processing. Indeed, numerous effects of estrogens on neuronal function as well as synaptic remodeling have been documented (Flanagan-Cato, 2000; Goodman et al, 2004; King and Seiler, 1988; Kurunczi et al, 2009; Luine et al, 1998; Parducz et al, 2006; Spencer et al, 2008; Zurkovsky et al, 2006; Zurkovsky et al, 2007). Moreover, effects on neural processes induced by the profound loss of circulating estrogens following ovariectomy have also been reported (Beltran-Campos et al, 2011; Das et al, 2002; King and Seiler, 1988; Vaucher et al, 2001).…”