The Role of the Hippocampus in Avoidance Learning and Anxiety Vulnerability

Abstract

The hippocampus has been implicated in anxiety disorders and post-traumatic stress disorder (PTSD); human studies suggest that a dysfunctional hippocampus may be a vulnerability factor for the development of PTSD. In the current study, we examined the effect of hippocampal damage in avoidance learning, as avoidance is a core symptom of all anxiety disorders. First, the effect of hippocampal damage on avoidance learning was investigated in outbred Sprague Dawley (SD) rats. Second, the function of the hippocampus in Wistar-Kyoto (WKY) rats was compared to SD rats. The WKY rat is an animal model of behavioral inhibition, a risk factor for anxiety, and demonstrates abnormal avoidance learning, marked by facilitated avoidance acquisition and resistance to extinction. The results of the current study indicate that hippocampal damage in SD rats leads to impaired extinction of avoidance learning similar to WKY rats. Furthermore, WKY rats have reduced hippocampal volume and impaired hippocampal synaptic plasticity as compared to SD rats. These results suggest that hippocampal dysfunction enhances the development of persistent avoidance responding and, thus, may confer vulnerability to the development of anxiety disorders and PTSD.

Avoidance symptoms and delayed verbal memory are associated with post-traumatic stress symptoms in female victims of sexual violence

“…The hippocampus has been known to be especially sensitive to the effects of stress (Diamond et al, 1996;Luine et al, 1994). A recent animal experimental study suggesting that hippocampal dysfunction enhances the development of persistent avoidance responding, and thus may confer vulnerability to the development of PTSD (Cominski et al, 2014). Our result is in line with studies mentioned above that suggest the involvement of the hippocampus in PTSD development.…”

Dysfunction in amygdala–prefrontal plasticity and extinction-resistant avoidance: A model for anxiety disorder vulnerability

“…Electrophysiology protocol was as previously described Cominski et al (2014) with minor adaptations. Naïve rats were anesthetized with urethane (1.5g/kg, i.p.)…”

Behavior and the cholinergic parameters in olfactory bulbectomized female rodents: Difference between rats and mice

“…Thus, we can conclude that the OBX rats showed more rapid acquisition and efficient recall of two-way active avoidance. Taking into account that a damage to the hippocampus may substantially improve active avoidance learning [59][60][61], enhance the development of persistent avoidance responding, and trouble its extinction [63], we can suppose that the development and maintenance of two-way active avoidance in our experiment may be related to hippocampal lesion induced by OBX. Additionally, data on the impairment of long-term potentiation [18], cellular morphology (present study, [32,33]), and dendritic atrophy [10] in the hippocampus after OBX also support our hypothesis.…”

“…This may also indicate the compromised hippocampal function in the animals with OBX because lesion to the hippocampus or their main inputs is known to facilitate the acquisition of the active-avoidance response [59][60][61][62][63].…”