The ROCK Inhibitor Fasudil Prevents Chronic Restraint Stress-Induced Depressive-Like Behaviors and Dendritic Spine Loss in Rat Hippocampus

Abstract

Background:Dendritic arbor simplification and dendritic spine loss in the hippocampus, a limbic structure implicated in mood disorders, are assumed to contribute to symptoms of depression. These morphological changes imply modifications in dendritic cytoskeleton. Rho GTPases are regulators of actin dynamics through their effector Rho kinase. We have reported that chronic stress promotes depressive-like behaviors in rats along with dendritic spine loss in apical dendrites of hippocampal pyramidal neurons, changes associated with Rho kinase activation. The present study proposes that the Rho kinase inhibitor Fasudil may prevent the stress-induced behavior and dendritic spine loss.Methods:Adult male Sprague-Dawley rats were injected with saline or Fasudil (i.p., 10 mg/kg) starting 4 days prior to and maintained during the restraint stress procedure (2.5 h/d for 14 days). Nonstressed control animals were injected with saline or Fasudil for 18 days. At 24 hours after treatment, forced swimming test, Golgi-staining, and immuno-western blot were performed.Results:Fasudil prevented stress-induced immobility observed in the forced swimming test. On the other hand, Fasudil-treated control animals showed behavioral patterns similar to those of saline-treated controls. Furthermore, we observed that stress induced an increase in the phosphorylation of MYPT1 in the hippocampus, an exclusive target of Rho kinase. This change was accompanied by dendritic spine loss of apical dendrites of pyramidal hippocampal neurons. Interestingly, increased pMYPT1 levels and spine loss were both prevented by Fasudil administration.Conclusion:Our findings suggest that Fasudil may prevent the development of abnormal behavior and spine loss induced by chronic stress by blocking Rho kinase activity.

Chronic Stress Triggers Expression of Immediate Early Genes and Differentially Affects the Expression of AMPA and NMDA Subunits in Dorsal and Ventral Hippocampus of Rats

“…Thus, our findings may underlie the reduced LTP reported in DH after chronic stress (Pavlides et al, 2002 ; Alfarez et al, 2003 ). Although we do not know whether subunit stoichiometry of NMDARs changed at synaptic sites, we can suggest that the reduction in PSD-95 may be indicative of the reduction in dendritic spines of CA1 subfield previously observed in our stress model (Fernández-Guasti et al, 2012 ; Castañeda et al, 2015 ; García-Rojo et al, 2017 ).…”

“…Preclinical studies have indicated that chronic stress exerts detrimental effects on excitatory synapses and on brain function in diverse areas related with cognitive and emotional control of reward behaviors, which resemble those observed in depressed individuals. In previous studies, others and we have described structural changes in hippocampus in response to chronic stress exposure (Magariños and McEwen, 1995 ; Castañeda et al, 2015 ; Pinto et al, 2015 ; García-Rojo et al, 2017 ). These include reduction in the number of dendritic spines in CA1 neurons of the DH (Castañeda et al, 2015 ; García-Rojo et al, 2017 ) associated with altered synaptic remodeling, which suggests altered glutamatergic circuitry.…”

“…In previous studies, others and we have described structural changes in hippocampus in response to chronic stress exposure (Magariños and McEwen, 1995 ; Castañeda et al, 2015 ; Pinto et al, 2015 ; García-Rojo et al, 2017 ). These include reduction in the number of dendritic spines in CA1 neurons of the DH (Castañeda et al, 2015 ; García-Rojo et al, 2017 ) associated with altered synaptic remodeling, which suggests altered glutamatergic circuitry. Some studies have highlighted a possible role for glutamate receptor subunits in stress-induced depressive-like behavior susceptibility (Duman, 2014 ).…”

“…All procedures were carried out during the light phase of the light-dark cycle. The restraint stress procedure was carried out between 9:00 and 12:00, as previously described (Bravo et al, 2009 ; Ulloa et al, 2010 ; Castañeda et al, 2015 ; García-Rojo et al, 2017 ). Briefly, rats were placed in a transparent plexiglass tube (25 × 8 cm) during 2.5 h for 14 consecutive days.…”

MicroRNA Profiling and Bioinformatics Target Analysis in Dorsal Hippocampus of Chronically Stressed Rats: Relevance to Depression Pathophysiology

“…Studies conducted in rodents under chronic stress models that recapitulate several symptoms of MDD have revealed changes in several forms of hippocampal neuroplasticity ( Kim et al, 2015 ). Chronically stressed rodents show several cyto-architecture modifications in the hippocampus, including dendritic arbor simplification ( Pinto et al, 2015 ) and dendritic spine loss in CA1 pyramidal neurons ( Castaneda et al, 2015 ; Garcia-Rojo et al, 2017 ), changes that have been linked to reduced expression of the brain derived neurotrophic factor (BDNF) ( Smith et al, 1995 ). Furthermore, chronic stress impairs hippocampus-dependent memory ( Conrad et al, 1996 ), which can be associated with changes in the two forms of synaptic efficacy; i.e., long-term potentiation (LTP) and long-term depression (LTD) ( Kim et al, 2015 ).…”