Changes In Spine Density Research Articles

Loss of Prestin Does Not Alter the Development of Auditory Cortical Dendritic Spines

Disturbance of sensory input during development can have disastrous effects on the development of sensory cortical areas. To examine how moderate perturbations of hearing can impact the development of primary auditory cortex, we examined markers of excitatory synapses in mice who lacked prestin, a protein responsible for somatic electromotility of cochlear outer hair cells. While auditory brain stem responses of these mice show an approximately 40 dB increase in threshold, we found that loss of prestin produced no changes in spine density or morphological characteristics on apical dendrites of cortical layer 5 pyramidal neurons. PSD-95 immunostaining also showed no changes in overall excitatory synapse density. Surprisingly, behavioral assessments of auditory function using the acoustic startle response showed only modest changes in prestin KO animals. These results suggest that moderate developmental hearing deficits produce minor changes in the excitatory connectivity of layer 5 neurons of primary auditory cortex and surprisingly mild auditory behavioral deficits in the startle response.

DGKι regulates presynaptic release during mGluR-dependent LTD

Diacylglycerol (DAG) is an important lipid second messenger. DAG signalling is terminated by conversion of DAG to phosphatidic acid (PA) by diacylglycerol kinases (DGKs). The neuronal synapse is a major site of DAG production and action; however, how DGKs are targeted to subcellular sites of DAG generation is largely unknown. We report here that postsynaptic density (PSD)-95 family proteins interact with and promote synaptic localization of DGKι. In addition, we establish that DGKι acts presynaptically, a function that contrasts with the known postsynaptic function of DGKζ, a close relative of DGKι. Deficiency of DGKι in mice does not affect dendritic spines, but leads to a small increase in presynaptic release probability. In addition, DGKι-/- synapses show a reduction in metabotropic glutamate receptor-dependent long-term depression (mGluR-LTD) at neonatal (∼2 weeks) stages that involve suppression of a decrease in presynaptic release probability. Inhibition of protein kinase C normalizes presynaptic release probability and mGluR-LTD at DGKι-/- synapses. These results suggest that DGKι requires PSD-95 family proteins for synaptic localization and regulates presynaptic DAG signalling and neurotransmitter release during mGluR-LTD.

Estradiol reduces dendritic spine density in the ventral striatum of female Syrian hamsters

Estradiol affects a variety of brain regions by modulating physiological and cellular functions as well as neuronal morphology. Within the striatum, estradiol is known to induce physiological and molecular changes, yet estradiol's effects on striatal dendritic morphology have not yet been evaluated. Using ballistic delivery of the lipophilic dye DiI to tissue sections, we were able to evaluate estradiol's effects on striatal morphology in female Syrian hamsters. We found that estradiol significantly decreased spine density within the nucleus accumbens core, with no effect in the nucleus accumbens shell or caudate. Interestingly, estradiol treatment caused a significant deconstruction of spines from more to less mature spine subtypes in both the nucleus accumbens core and shell regardless of changes in spine density. These results are significant in that they offer a novel mechanism for estradiol actions on a wide variety of nucleus accumbens functions such as motivation or reward as well as their pathological consequences (e.g. drug addiction).

Phosphate and carbonate salts of calcium support robust bone building in osteoporosis

Calcium is an essential cotherapy in osteoporosis treatment. The relative effectiveness of various calcium salts for this purpose is uncertain. Many older women with osteoporosis have phosphorus intakes of <70% of the Recommended Dietary Allowance. Our objective was to test the hypothesis that calcium phosphate would better support anabolic bone building than would calcium carbonate. This study was a 12-mo, randomized, positive-comparator, 2-arm, single-blind clinical trial in 211 patients treated with teriparatide who consumed <1000 mg phosphorus/d. Participants were randomly assigned to receive, in addition to teriparatide and 1000 IU cholecalciferol, 1800 mg calcium/d as either tricalcium phosphate or calcium carbonate. The primary endpoints were changes in lumbar spine and total hip bone mineral densities (BMDs); secondary endpoints were changes in bone resorption biomarkers and serum and urine calcium and phosphorus concentrations. In the combined group, the lumbar spine BMD increased by 7.2%, and total hip BMD increased by 2.1% (P < 0.01 for both). However, there was no significant difference between calcium-treatment groups, and there were no significant between-group differences in serum calcium and phosphorus concentrations or in urine calcium concentrations. Bone resorption biomarkers increased in both groups, as expected with teriparatide, but the increases in the 2 calcium groups did not differ significantly. Tricalcium phosphate and calcium carbonate appear to be approximately equally effective in supporting bone building with a potent anabolic agent; phosphate salt may be preferable in patients with restricted phosphorus intakes. This trial was registered at clinicaltrials.gov as NCT00074711.

Selective changes in thin spine density and morphology in monkey prefrontal cortex correlate with aging-related cognitive impairment.

Age-associated memory impairment (AAMI) occurs in many mammalian species, including humans. In contrast to Alzheimer's disease (AD), in which circuit disruption occurs through neuron death, AAMI is due to circuit and synapse disruption in the absence of significant neuron loss and thus may be more amenable to prevention or treatment. We have investigated the effects of aging on pyramidal neurons and synapse density in layer III of area 46 in dorsolateral prefrontal cortex of young and aged, male and female rhesus monkeys (Macaca mulatta) that were tested for cognitive status through the delayed non-matching-to-sample (DNMS) and delayed response tasks. Cognitive tests revealed an age-related decrement in both acquisition and performance on DNMS. Our morphometric analyses revealed both an age-related loss of spines (33%, p < 0.05) on pyramidal cells and decreased density of axospinous synapses (32%, p < 0.01) in layer III of area 46. In addition, there was an age-related shift in the distribution of spine types reflecting a selective vulnerability of small, thin spines, thought to be particularly plastic and linked to learning. While both synapse density and the overall spine size average of an animal were predictive of number of trials required for acquisition of DNMS (i.e., learning the task), the strongest correlate of behavior was found to be the head volume of thin spines, with no correlation between behavior and mushroom spine size or density. No synaptic index correlated with memory performance once the task was learned.

Changes in dendritic morphology and spine density in motor cortex of the adult rat after stroke during infancy

Cognitive and motor deficits are pervasive in children that suffer early brain injury. The aim of this study was to determine the impact that early damage has on dendritic spine density and other aspects of dendritic morphology of neurons in the motor cortex. Also of interest was how changes in dendritic structure evolved across the lifespan. Ischemia was induced in 10-day-old Long Evans rats by injection of Rose Bengal dye and a laser positioned over right motor cortex. Animals were sacrificed at two and six months of age, and brains were processed for Golgi-Cox staining. Animals exposed to early damage exhibited increases in length of basilar dendrites at two months of age, however no differences in spine density were found across groups at this age. At six months of age, injured animals demonstrated an overall decrease in apical and basilar spine density. Our results suggest that the changes in dendritic length and spine density observed after early damage are unable to be maintained as the animal ages. The observation that increases in spine density do not necessarily coincide with increases in dendritic length suggests that the two processes may not be dependent on one another and suggest two independent plasticity processes responding to damage.

Dopamine D1 and N-methyl-d-aspartate receptors and extracellular signal-regulated kinase mediate neuronal morphological changes induced by repeated cocaine administration

The development of drug addiction involves persistent cellular and molecular changes in the CNS. The brain dopamine and glutamate systems play key roles in mediating drug-induced neuroadaptation. Changes in dendritic morphology in medium spiny neurons (MSNs) in the nucleus accumbens (NAc) and caudate putamen (CPu) accompany drug-induced enduring behavioral and molecular changes. We have investigated the potential involvement of dopamine D1 and D2 receptors, the N-methyl-d-aspartate (NMDA) receptor, and the extracellular signal-regulated kinase (ERK) in dendritic morphological changes induced by repeated cocaine administration. We show that either a genetic mutation or pharmacological blockade of dopamine D1 receptors attenuated cocaine-induced changes in both dendritic branching and spine density of MSNs in the shell of the NAc and CPu. In contrast, antagonism of dopamine D2 receptors had no obvious effect on changes in dendritic branching but had a partial effect on changes in spine density of MSNs in these brain regions following repeated cocaine injections. Pharmacological inhibition of either NMDA receptors or ERK attenuated cocaine-induced changes in both dendritic branching and spine density of MSNs in the shell of the NAc and CPu. These results suggest that dopamine D1 and NMDA receptors and ERK contribute significantly to neuronal morphological changes induced by repeated exposure to cocaine.

Effect of oral clodronate on bone mass, bone turnover and subsequent metastases in women with primary breast cancer

Breast cancer treatments have been associated with accelerated bone loss and increased osteoporosis risk. In a subgroup analysis of a randomised, double-blind, placebo-controlled study, we compared the changes in spine and total hip bone mineral density (BMD) and biochemical markers of bone turnover in women with primary breast cancer who had received standard therapy plus either oral clodronate 1600 mg/d ( n = 419) or placebo ( n = 432) for 2 years. After 2 years, spine BMD was 1.92% higher in patients who received clodronate instead of placebo ( P < 0.0001) and total hip BMD was 1.29% higher ( P = 0.002 versus placebo). Patients who received clodronate had a median 26% reduction in levels of serum N-terminal pro-peptide of type I procollagen (PINP) – a marker of bone turnover – after 2 years of therapy. This compares with a median 5% increase in patients who received placebo ( P < 0.0001). Effects on BMD, but not biochemical markers, persisted for up to 3 years post-treatment. Early changes in PINP were associated with changes in BMD and the likelihood of developing bone metastases. This study shows the use of oral clodronate during primary breast cancer treatment is associated with reduced bone turnover and protection against bone metastases.

Effects of teriparatide versus alendronate for treating glucocorticoid‐induced osteoporosis: Thirty‐six–month results of a randomized, double‐blind, controlled trial

To compare the bone anabolic drug teriparatide (20 microg/day) with the antiresorptive drug alendronate (10 mg/day) for treating glucocorticoid-induced osteoporosis (OP). This was a 36-month, randomized, double-blind, controlled trial in 428 subjects with OP (ages 22-89 years) who had received > or =5 mg/day of prednisone equivalent for > or =3 months preceding screening. Measures included changes in lumbar spine and hip bone mineral density (BMD), changes in bone biomarkers, fracture incidence, and safety. Increases in BMD from baseline were significantly greater in the teriparatide group than in the alendronate group, and at 36 months were 11.0% versus 5.3% for lumbar spine, 5.2% versus 2.7% for total hip, and 6.3% versus 3.4% for femoral neck (P < 0.001 for all). In the teriparatide group, median percent increases from baseline in N-terminal type I procollagen propeptide (PINP) and osteocalcin (OC) levels were significant from 1 to 36 months (P < 0.01), and increases in levels of C-terminal telopeptide of type I collagen (CTX) were significant from 1 to 6 months (P < 0.01). In the alendronate group, median percent decreases in PINP, OC, and CTX were significant by 6 months and remained below baseline through 36 months (P < 0.001). Fewer subjects had vertebral fractures in the teriparatide group than in the alendronate group (3 [1.7%] of 173 versus 13 [7.7%] of 169; P = 0.007), with most occurring during the first 18 months. There was no significant difference between groups in the incidence of nonvertebral fractures (16 [7.5%] of 214 subjects taking teriparatide versus 15 [7.0%] of 214 subjects taking alendronate; P = 0.843). More subjects in the teriparatide group (21%) versus the alendronate group (7%) had elevated predose serum calcium concentrations (P < 0.001). Our findings indicate that subjects with glucocorticoid-induced OP treated with teriparatide for 36 months had greater increases in BMD and fewer new vertebral fractures than subjects treated with alendronate.

Prenatal exposure to moderate levels of ethanol alters social behavior in adult rats: Relationship to structural plasticity and immediate early gene expression in frontal cortex

The goals of the present study were to characterize the effects of prenatal exposure to moderate levels of ethanol on adult social behavior, and to evaluate fetal-ethanol-related effects on dendritic morphology, structural plasticity and activity-related immediate early gene (IEG) expression in the agranular insular (AID) and prelimbic (Cg3) regions of frontal cortex. Baseline fetal-ethanol-related alterations in social behavior were limited to reductions in social investigation in males. Repeated experience with novel cage-mates resulted in comparable increases in wrestling and social investigation among saccharin- and ethanol-exposed females, whereas social behavioral effects among males were more evident in ethanol-exposed animals. Male ethanol-exposed rats also displayed profound increases in wrestling when social interaction was motivated by 24 h of isolation. Baseline decreases in dendritic length and spine density in AID were observed in ethanol-exposed rats that were always housed with the same cage-mate. Modest experience-related decreases in dendritic length and spine density in AID were observed in saccharin-exposed rats housed with various cage-mates. In contrast, fetal-ethanol-exposed rats displayed experience-related increases in dendritic length in AID, and no experience-related changes in spine density. The only effect observed in Cg3 was a baseline increase in basilar dendritic length among male ethanol-exposed rats. Robust increases in activity-related IEG expression in AID (c- fos and Arc) and Cg3 (c- fos) were observed following social interaction in saccharin-exposed rats, however, activity-related increases in IEG expression were not observed in fetal-ethanol-exposed rats in either region. The results indicate that deficits in social behavior are among the long-lasting behavioral consequences of moderate ethanol exposure during brain development, and implicate AID, and to a lesser degree Cg3, in fetal-ethanol-related social behavior abnormalities.

EphB Maintains Dendritic Spine Morphology through Focal Adhesion Kinase: Figure 1.

The postsynaptic components of excitatory synapses are located at specialized structures called dendritic spines, small protrusions along neuronal dendrites. Dendritic spines are not static, and changes in spine size, shape, and density are believed to be associated with synaptic plasticity and

Effect of the environment on the dendritic morphology of the rat auditory cortex

The present study aimed to identify morphological correlates of environment-induced changes at excitatory synapses of the primary auditory cortex (A1). We used the Golgi-Cox stain technique to compare pyramidal cells dendritic properties of Sprague-Dawley rats exposed to different environmental manipulations. Sholl analysis, dendritic length measures, and spine density counts were used to monitor the effects of sensory deafness and an auditory version of environmental enrichment (EE). We found that deafness decreased apical dendritic length leaving basal dendritic length unchanged, whereas EE selectively increased basal dendritic length without changing apical dendritic length. On the contrary, deafness decreased while EE increased spine density in both basal and apical dendrites of A1 Layer 2/3 (LII/III) neurons. To determine whether stress contributed to the observed morphological changes in A1, we studied neural morphology in a restraint-induced model that lacked behaviorally relevant acoustic cues. We found that stress selectively decreased apical dendritic length in the auditory but not in the visual primary cortex. Similar to the acoustic manipulation, stress-induced changes in dendritic length possessed a layer-specific pattern displaying LII/III neurons from stressed animals with normal apical dendrites but shorter basal dendrites, while infragranular neurons (Layers V and VI) displayed shorter apical dendrites but normal basal dendrites. The same treatment did not induce similar changes in the visual cortex, demonstrating that the auditory cortex is an exquisitely sensitive target of neocortical plasticity, and that prolonged exposure to different acoustic as well as emotional environmental manipulation may produce specific changes in dendritic shape and spine density.

Dendritic Spine Remodeling After Spinal Cord Injury Alters Neuronal Signal Processing

Central sensitization, a prolonged hyperexcitability of dorsal horn nociceptive neurons, is a major contributor to abnormal pain processing after spinal cord injury (SCI). Dendritic spines are micron-sized dendrite protrusions that can regulate the efficacy of synaptic transmission. Here we used a computational approach to study whether changes in dendritic spine shape, density, and distribution can individually, or in combination, adversely modify the input-output function of a postsynaptic neuron to create a hyperexcitable neuronal state. The results demonstrate that a conversion from thin-shaped to more mature, mushroom-shaped spine structures results in enhanced synaptic transmission and fidelity, improved frequency-following ability, and reduced inhibitory gating effectiveness. Increasing the density and redistributing spines toward the soma results in a greater probability of action potential activation. Our results demonstrate that changes in dendritic spine morphology, documented in previous studies on spinal cord injury, contribute to the generation of pain following SCI.

Age-Dependent Impairment of Spine Morphology and Synaptic Plasticity in Hippocampal CA1 Neurons of a Presenilin 1 Transgenic Mouse Model of Alzheimer's Disease

Presenilin 1 (PS1) mutations are responsible for a majority of early onset familial Alzheimer's disease (FAD) cases, in part by increasing the production of Abeta peptides. However, emerging evidence suggests other possible effects of PS1 on synaptic dysfunction where PS1 might contribute to the pathology independent of Abeta. We chose to study the L286V mutation, an aggressive FAD mutation which has never been analyzed at the electrophysiological and morphological levels. In addition, we analyzed for the first time the long term effects of wild-type human PS1 overexpression. We investigated the consequences of the overexpression of either wild-type human PS1 (hPS1) or the L286V mutated PS1 variant (mutPS1) on synaptic functions by analyzing synaptic plasticity and associated spine density changes from 3 to 15 months of age. We found that mutPS1 induces a transient increase observed only in 4- to 5-month-old mutPS1 animals in NMDA receptor (NMDA-R)-mediated responses and LTP compared with hPS1 mice and nontransgenic littermates. The increase in synaptic functions is concomitant with an increase in spine density. With increasing age, however, we found that the overexpression of human wild-type PS1 progressively decreased NMDA-R-mediated synaptic transmission and LTP, without neurodegeneration. These results identify for the first time a transient increase in synaptic function associated with L286V mutated PS1 variant in an age-dependent manner. In addition, they support the view that the PS1 overexpression promotes synaptic dysfunction in an Abeta-independent manner and underline the crucial role of PS1 during both normal and pathological aging.

Estrogen receptor alpha and beta specific agonists regulate expression of synaptic proteins in rat hippocampus

Changes in hippocampal CA1 dendritic spine density and synaptic number across the estrous cycle in female rats correlate with increased hippocampal-dependent cognitive performance in a manner that is dependent on estrogen receptors (ERs). Two isoforms of the estrogen receptor, α and β are present in the rat hippocampus and distinct effects on cognitive behavior have been described for each receptor. The present study generated a profile of synaptic proteins altered by administration of estradiol benzoate, the ERα selective agonist PPT (1,3,5-tris (4-hydroxyphenyl)-4-propyl-1H-pyrazole) and the ERβ selective agonist DPN (2,3-bis (4-hydroxyphenyl) propionitrile) alone and in combination in comparison to vehicle in the CA1 region of the dorsal hippocampus. In the stratum radiatum, estradiol, DPN, and PPT increased PSD-95 and AMPA-type glutamate receptor subunit GluR1. Only DPN administration regulated expression of AMPA receptor subunits GluR2 and GluR3, increasing and decreasing levels respectively. DPN also increased GluR2 expression in the other lamina of the CA1. These results support previous reports that estradiol and isoform specific agonists differentially activate ERα and ERβ to regulate protein expression. The distinct effects of DPN and PPT administration on synaptic proteins suggest that the desired therapeutic outcome of estrogen may be accomplished by using specific estrogen receptor agonists. Moreover, the effects of estradiol treatment on PSD-95 expression are consistent with a growing body of evidence that this postsynaptic protein is a key marker of estrogen action related to spine synapse formation.

The Formation of Recent and Remote Memory Is Associated with Time-Dependent Formation of Dendritic Spines in the Hippocampus and Anterior Cingulate Cortex

Although hippocampal-cortical interactions are crucial for the formation of enduring declarative memories, synaptic events that govern long-term memory storage remain mostly unclear. We present evidence that neuronal structural changes, i.e., dendritic spine growth, develop sequentially in the hippocampus and anterior cingulate cortex (aCC) during the formation of recent and remote contextual fear memory. We found that mice placed in a conditioning chamber for one 7 min conditioning session and exposed to five footshocks (duration, 2 s; intensity, 0.7 mA; interstimulus interval, 60 s) delivered through the grid floor exhibited robust fear response when returned to the experimental context 24 h or 36 d after the conditioning. We then observed that their fear response at the recent, but not the remote, time point was associated with an increase in spine density on hippocampal neurons, whereas an inverse temporal pattern of spine density changes occurred on aCC neurons. At each time point, hippocampal or aCC structural alterations were achieved even in the absence of recent or remote memory tests, thus suggesting that they were not driven by retrieval processes. Furthermore, ibotenic lesions of the hippocampus impaired remote memory and prevented dendritic spine growth on aCC neurons when they were performed immediately after the conditioning, whereas they were ineffective when performed 24 d later. These findings reveal that gradual structural changes modifying connectivity in hippocampal-cortical networks underlie the formation and expression of remote memory, and that the hippocampus plays a crucial but time-limited role in driving structural plasticity in the cortex.

Autometallographic enhancement of the Golgi-Cox staining enables high resolution visualization of dendrites and spines

We present a method for autometallographic (AMG) enhancement of the Golgi-Cox staining enabling high resolution visualization of dendrites and spines. The method is cheaper and more flexible than conventional enhancement procedures performed with commercial photographic developers. The staining procedure is thoroughly described and we demonstrate with qualitative and quantitative data, how histological tissue sectioning, Golgi-Cox immersion time and different AMG enhancement length may influence the staining of dendrites and spines in the rat hippocampus. The described method will be of value for future behavioural-anatomical studies, examining changes in dendrite branching and spine density caused by brain diseases and their subsequent treatment.

Subchronic treatment with 17alpha‐ethynil estradiol partially recovers the ability of ovariectomized rats to learn an autoshaped task

Estrogen induces cyclic changes in synapse formation and spine density of the hippocampus and increases the synthesis of acetylcholine in basal forebrain. This information leads one to consider that estrogen could have effect on hippocampus‐dependent cognitive functions such as memory and learning. In contrast, ovariectomy‐induced (OVX) long‐term absence of estrogens seems to be responsible for deterioration in cognitive processes.Removal of ovaries in rats was early used as a model for post‐menopausal osteoporosis. Recently, this surgery has been proposed to study the human post‐menopause. Since cognitive abilities decrease during this non reproductive condition of human females, it is likely that rats display a similar decrease of cognitive capabilities after long‐term OVX. This study was designed to analyze the performance of rats in an autoshaped task at different times after OVX. Under these experimental circumstances, the role of the synthetic estrogen 17alpha‐ethynil estradiol was tested. Results show a loss of the capacity of learning in the aforementioned task 12 weeks after OVX. At the same time, ethynilestradiol partially reduced these actions. These long‐term effects of OVX support the idea that this surgical manipulation could be a useful model for understanding some alterations associated to human post‐menopause. Support; COFAA and SIP‐IPN.

Altered Dendritic Spine Plasticity in Cocaine-Withdrawn Rats

Chronic cocaine treatment is associated with changes in dendritic spines in the nucleus accumbens, but it is unknown whether this neuroplasticity alters the effect of a subsequent cocaine injection on spine morphology and protein content. Three weeks after daily cocaine or saline administration, neurons in the accumbens were filled with the lipophilic dye, DiI. Although daily cocaine pretreatment did not alter spine density compared with daily saline, there was a shift from smaller to larger diameter spines. During the first 2 h after an acute cocaine challenge, a bidirectional change in spine head diameter and increase in spine density was measured in daily cocaine-pretreated animals. In contrast, no change in spine diameter or density was elicited by a cocaine challenge in daily saline animals during the first 2 h after injection. However, spine density was elevated at 6 h after a cocaine challenge in daily saline-pretreated animals. The time-dependent profile of proteins in the postsynaptic density subfraction elicited by a cocaine challenge in daily cocaine-pretreated subjects indicated that the changes in spine diameter and density were associated with a deteriorating actin cytoskeleton and a reduction in glutamate signaling-related proteins. Correspondingly, the amplitude of field potentials in accumbens evoked by stimulating prefrontal cortex was reduced for up to 6 h after acute cocaine in daily cocaine-withdrawn animals. These data indicate that daily cocaine pretreatment dysregulates dendritic spine plasticity elicited by a subsequent cocaine injection.

Stress-induced dendritic remodeling in the prefrontal cortex is circuit specific.

Chronic stress exposure has been reported to induce dendritic remodeling in several brain regions, but it is not known whether individual neural circuits show distinct patterns of remodeling. The current study tested the hypothesis that the projections from the infralimbic (IL) area of the medial prefrontal cortex (mPFC) to the basolateral nucleus of the amygdala (BLA), a pathway relevant to stress-related mental illnesses like depression and post-traumatic stress disorder, would have a unique pattern of remodeling in response to chronic stress. The retrograde tracer FastBlue was injected into male rats' BLA or entorhinal cortex (EC) 1 week prior to 10 days of immobilization stress. After cessation of stress, FastBlue-labeled and unlabeled IL pyaramidal neurons were loaded with fluorescent dye Lucifer Yellow to visualize dendritic arborization and spine density. As has been previously reported, randomly selected (non-FastBlue-labeled) neurons showed stress-induced dendritic retraction in apical dendrites, an effect also seen in EC-projecting neurons. In contrast, BLA-projecting neurons showed no remodeling with stress, suggesting that this pathway may be particularly resilient against the effects of stress. No neurons showed stress-related changes in spine density, contrasting with reports that more dorsal areas of the mPFC show stress-induced decreases in spine density. Such region- and circuit-specificity in response to stress could contribute to the development of stress-related mental illnesses.