Steroid modulation of hippocampal plasticity: switching between cognitive and emotional memories

Abstract

Several new observations have shifted the view of the hippocampus from a structure in charge of cognitive processes to a brain area that participates in the formation of emotional memories, in addition to its role in cognition. Specifically, while the dorsal hippocampus is involved in the processing of cognitive memories; the ventral sector is mainly associated with the control of behavioral inhibition, stress, and emotional memory. Stress is likely to cause this switch in control of hippocampal functions by modulating synaptic plasticity in the dorsal and ventral sectors of the hippocampus through the differential activation of mineralocorticosteroid or glucocorticosteroid receptors. Herein, we will review the effects of stress hormones on synaptic plasticity in the hippocampus and outline the outcomes on stress-related global functions of this structure. We propose that steroid hormones act as molecular switches: by changing the strength of synaptic connectivity in the hippocampus following stress, they regulate the routes by which the hippocampus is functionally linked to the rest of the brain. This hypothesis has profound implications for the pathophysiology of psychiatric disorders.

Preferential loss of dorsal-hippocampus synapses underlies memory impairments provoked by short, multi-modal stress

“…This differential loss of dorsal CA1 synapses may lead to disrupted function of the memory networks associated with dorsal hippocampus. 9,15 The current findings are congruent with previous studies showing that stress can influence the number of synapses already within hours 40,55 in brain regions including the hippocampus. 26,34,42 Neurotransmitters, including norepinephrine, [76][77][78] serotonin [79][80][81] and glutamate, 82,83 as well as stress-induced release of neuropeptides 26,34,84,85 and steroids, [86][87][88] can influence synapse number and function.…”

“…9,11,13 In addition, stress and glucocorticoids affect synaptic plasticity differentially along the hippocampal dorsoventral axis, impairing long-term potentiation in dorsal hippocampus, but enhancing this process in ventral hippocampus. 15,49,118 The current results further support the distinct roles of dorsal and ventral hippocampus and indicate that multimodal stress may influence them selectively in a manner unique from that of restraint stress.…”

“…9,14 Stress and stress hormones influence dorsal and ventral hippocampus differentially: chronic stress attenuates long-term potentiation in dorsal, but not ventral CA1, suggesting that discrete mechanisms exist for the effects of stress mediators on dorsoventral components of the hippocampal formation. 15 The effects of stress on memory have received intense investigation, showing that the duration of stress, for example, acute vs chronic, crucially influences its effect on memory function. [16][17][18][19][20][21] However, the potential importance of the complexity of stress has not been clarified.…”

Stress In Utero: Prenatal Programming of Brain Plasticity and Cognition

“…Subsequent studies proposed that corticosterone affects glutamate receptor distribution and kinetics (62,63). Corticosterone and stress affect other neurotransmitter systems, including GABA, as well as the expression of several peptides and growth factors (64,65). Early studies on the effects of PS on LTP did not present a coherent picture.…”

Stress and Steroid regulation of synaptic transmission: from physiology to pathophysiology

“…The main section of the Frontier Topic involves novel views on postsynaptic effects of steroid hormones, CRH, and noradrenaline on synaptic functions in the brain. These include a section on amygdala-hippocampus interaction (Li and Richter-Levin, 2012), cellular, and molecular studies on CRH effects in the hippocampus (Chen et al, 2012), effects of early life stress on metabolic functions in the brain (Bock et al, 2012), interactions between noradrenaline and corticosterone on brain function (Krugers et al, 2012), region selective effects of corticosterone in the hippocampus (Maggio and Segal, 2012), and finally, effects of corticosterone on NMDA receptor function in the hippocampus (Tse et al, 2012). Finally, a behavioral study on the interaction between gestational and adult stress (Walf and Frye, 2012) concludes the list.…”