Rat Cingulate Cortex Research Articles

Tandospirone prevents stress-induced anxiety-like behavior and visceral hypersensitivity by suppressing theta oscillation enhancement via 5-HT1A receptors in the anterior cingulate cortex in rats.

Tandospirone, a third-generation of antianxiety agent with fewer side effects, has been widely used in the treatment of anxiety. Moreover, it is interesting that tandospirone has been found to relieve gastrointestinal symptoms in patients with refractory irritable bowel syndrome who also have psychological dysfunctions. However, the underlying mechanism remains unclear. In this study, using a visceral hypersensitivity rat model induced by chronic water avoidance stress to mimic the symptoms of irritable bowel syndrome, we found that tandospirone relieved anxiety-like behavior and visceral hypersensitivity induced by stress. Meanwhile, stressed rats had increased 5-HT concentration, less 5-HT1A receptor expression, and enhanced theta oscillations in the anterior cingulate cortex (ACC). Furthermore, the power of the theta band in ACC is positively correlated with the level of visceral sensitivity. Activation of 5-HT1A receptors by its agonist, 8-OH-DPAT, to compensate for their effect in ACC reduced the enhancement of theta oscillations in ACC slices in stressed rats, whereas 5-HT1A receptor antagonist, WAY100135, facilitates theta oscillations in slices of normal rats. Tandospirone reduced the enhancement of theta band power in ACC in vitro and in vivo, thus alleviating anxiety-like behavior and visceral hypersensitivity through 5-HT1A receptors in stressed rats. These results suggest a novel mechanism by which tandospirone activates 5-HT1A receptors to relieve stress-induced anxiety and visceral hypersensitivity by suppressing theta oscillation enhancement in ACC.

Pro-cognitive effect of acute imipramine administration correlates with direct interaction of BDNF with its receptor, Trkβ

Given the important role of brain-derived neurotrophic factor (BDNF)-mediated Trkβ signalling in the mechanism of action of antidepressants (ADs), we examined ligand–receptor interactions in the rat cingulate cortex using a proximity ligation assay (PLA) in response to acute and repeated administration of imipramine (IMI), followed by various drug-free periods. Both the acute and chronic administration of IMI increased the BDNF-Trkβ interaction observed 3 h after drug administration. Withdrawal of IMI for 72 h or 7 days did not alter BDNF-Trkβ interaction. A significant reduction in this interaction after chronic IMI administration followed by 21 drug-free days was observed, but it returned to the control value when a new dose of IMI was given after this time. The level of mRNA encoding BDNF or Trkβ did not change in the experimental groups of animals, so one can conclude that alterations in the BDNF-Trkβ interaction depend not on acute vs. repeated treatment with IMI but on the presence of the drug in the body. This effect correlates well with the strong pro-cognitive effect of acute IMI, assessed by the novel object recognition (NOR) test.

The Increased Channel Activity of N-Methyl-D-Aspartate Receptors at Extrasynaptic Sites in the Anterior Cingulate Cortex of Neonatal Rats Following Prolonged Ketamine Exposure.

BackgroundKetamine is a dissociative anesthetic, commonly used for analgesia and anesthesia in a variety of pediatric procedures. It acts as a non-competitive antagonist to block ion channels of the N-methyl-D-aspartate receptors (NMDARs). Our previous study showed that repeated ketamine exposure developed a compensatory increase in NMDAR-mediated currents in neurons of the anterior cingulate cortex (ACC) of neonatal rats, and this increase was largely mediated by the GluN2B subunit-containing receptors, a predominant type of NMDARs during embryonic and early development of the brain. These data provide the molecular evidence to support that immature neurons are highly vulnerable to the development of apoptotic cell death after prolonged ketamine exposure.MethodsUsing whole-cell patch-clamp electrophysiology in an in vitro preparation of rat forebrain slices containing the ACC, the present study aimed at further determining whether GluN2B-containing NMDARs at extrasynaptic sites of immature neurons were the major target of ketamine for developing a compensatory increase in NMDAR-mediated synaptic transmission.ResultsOur major findings were that GluN2B subunits played a significant role in mediating ketamine-induced blockade of NMDAR-mediated currents in neonatal neurons and GluN2B-containing NMDARs expressed at extrasynaptic sites in neonatal neurons were the major player in compensatory enhancement of NMDAR-mediated currents after repeated ketamine exposure.ConclusionThese results provide new evidence to strongly indicate that GluN2B-containing NMDARs at extrasynaptic sites are the key molecule contributing to the high vulnerability of the neonatal brain to ketamine-induced neurotoxic effects.

Effects of chronic exposure to haloperidol, olanzapine or lithium on SV2A and NLGN synaptic puncta in the rat frontal cortex

Positron emission tomography studies using the synaptic vesicle glycoprotein 2A (SV2A) radioligand [11C]-UCB-J provide in vivo evidence for synaptic dysfunction and/or loss in the cingulate and frontal cortex of patients with schizophrenia. In exploring potential confounding effects of antipsychotic medication, we previously demonstrated that chronic (28-day) exposure to clinically relevant doses of haloperidol does not affect [3H]-UCB-J radioligand binding in the cingulate and frontal cortex of male rats. Furthermore, neither chronic haloperidol nor olanzapine exposure had any effect on SV2A protein levels in these brain regions. These data do not exclude the possibility, however, that more subtle changes in SV2A may occur at pre-synaptic terminals, or the post-synaptic density, following chronic antipsychotic drug exposure. Moreover, relatively little is known about the potential effects of psychotropic drugs other than antipsychotics on SV2A. To address these questions directly, we herein used immunostaining and confocal microscopy to explore the effect of chronic (28-day) exposure to clinically relevant doses of haloperidol, olanzapine or the mood stabilizer lithium on presynaptic SV2A, postsynaptic Neuroligin (NLGN) puncta and their overlap as a measure of total synaptic density in the rat prefrontal and anterior cingulate cortex. We found that, under the conditions tested here, exposure to antipsychotics had no effect on SV2A, NLGN, or overall synaptic puncta count. In contrast, chronic lithium exposure significantly increased NLGN puncta density relative to vehicle, with no effect on either SV2A or total synaptic puncta. Future studies are required to understand the functional consequences of these changes.

Chewing augments stress-induced increase of pERK-immunoreactive cells in the rat cingulate cortex

The eff ;ects of chewing during restraint stress on the anterior, mid- and posterior cingulate cortices were investigated in rats using immunohistochemistry to detect the expression of phosphorylated extracellular signal-regulated kinase 1 and 2 (pERK1/2), a marker of responding cells. The rats were divided into three groups: control (no immobilization), stress-only (immobilized), and stress-with-chewing (immobilized and allowed to chew a wooden stick). Significant increases in the number of pERK1/2-immunoreactive cells in the anterior, mid- and posterior cingulate cortices were noted in the stress-only group when compared with the control group (p < 0.05). Furthermore, the number of pERK1/2-immunoreactive cells in the anterior, mid- and posterior cingulate cortices in the stress-with-chewing group was also significantly higher than that in the stress-only group (p < 0.05).These findings indicate that the cingulate cortex plays a role in the negative-feedback effect and might be an essential part of the brain where the ameliorating effects of chewing against stress are produced.

Sex Differences in the Effect of Alcohol Drinking on Myelinated Axons in the Anterior Cingulate Cortex of Adolescent Rats.

Cognitive deficits associated with teenage drinking may be due to disrupted myelination of prefrontal circuits. To better understand how alcohol affects myelination, male and female Wistar rats (n = 7–9/sex/treatment) underwent two weeks of intermittent operant self-administration of sweetened alcohol or sweetened water early in adolescence (postnatal days 28–42) and we tested for macro- and microstructural changes to myelin. We previously reported data from the males of this study showing that alcohol drinking reduced myelinated fiber density in layers II–V of the anterior cingulate division of the medial prefrontal cortex (Cg1); herein, we show that myelinated fiber density was not significantly altered by alcohol in females. Alcohol drinking patterns were similar in both sexes, but males were in a pre-pubertal state for a larger proportion of the alcohol exposure period, which may have contributed to the differential effects on myelinated fiber density. To gain more insight into how alcohol impacts myelinated axons, brain sections from a subset of these animals (n = 6/sex/treatment) were used for microstructural analyses of the nodes of Ranvier. Confocal analysis of nodal domains, flanked by immunofluorescent-labeled contactin-associated protein (Caspr) clusters, indicated that alcohol drinking reduced nodal length-to-width ratios in layers II/III of the Cg1 in both sexes. Despite sex differences in the underlying cause (larger diameter axons after alcohol in males vs. shorter nodal lengths after alcohol in females), reduced nodal ratios could have important implications for the speed and integrity of neural transmission along these axons in both males and females. Alcohol-induced changes to myelinated axonal populations in the Cg1 may contribute to long-lasting changes in prefrontal function associated with early onset drinking.

Involvement of rat posterior prelimbic and cingulate area 2 in vocalization control.

Microstimulation mapping identified vocalization areas in primate anterior cingulate cortex. Rat anterior cingulate and medial prefrontal areas have also been intensely investigated, but we do not know, how these cortical areas contribute to vocalizations and no systematic mapping of stimulation‐evoked vocalizations has been performed. To address this question, we mapped microstimulation‐evoked (ultrasonic) vocalizations in rat cingulate and medial prefrontal cortex. The incidence of evoked vocalizations differed markedly between frontal cortical areas. Vocalizations were most often evoked in posterior prelimbic cortex and cingulate area 2, whereas vocalizations were rarely evoked in dorsal areas (vibrissa motor cortex, secondary motor cortex and cingulate area 1) and anterior areas (anterior prelimbic, medial‐/ventral‐orbital cortex). Vocalizations were observed at intermediate frequencies in ventro‐medial areas (infralimbic and dorsopeduncular cortex). Various complete, naturally occurring calls could be elicited. In prelimbic cortex superficial layer microstimulation evoked mainly fear calls with low efficacy, whereas deep layer microstimulation evoked mainly 50 kHz calls with high efficacy. Vocalization stimulation thresholds were substantial (70–500 μA, the maximum tested; on average ~400 μA) and latencies were long (median 175 ms). Posterior prelimbic cortex projected to numerous targets and innervated brainstem vocalization centers such as the intermediate reticular formation and the nucleus retroambiguus disynaptically via the periaqueductal gray. Anatomical position, stimulation effects and projection targets of posterior prelimbic cortex were similar to that of monkey anterior cingulate vocalization cortex. Our data suggest that posterior prelimbic cortex is more closely involved in control of vocalization initiation than in specifying acoustic details of vocalizations.

Role of Mu-Opioid Receptor in Nociceptive Modulation in the Anterior Cingulate Cortex of Rats with Inflammatory Pain

Objective: The present study was performed to explore the role of mu opioid receptor (MOR) in nociceptive modulation in anterior cingulate cortex (ACC) of rats with inflammatory pain. Methods: To set up an inflammatory pain model, rats received a subcutaneous injection of 0.1 ml of 2% carrageenan into the left hindpaw. The hindpaw withdrawal latency (HWL) to thermal and mechanical stimulation, by hot plate and Randall Selitto Test respectively, was used to evaluate the rat's responses to noxious stimulation. The effects induced by intra-ACC administration of morphine and opioid receptor antagonists were observed. The influence of inflammatory pain on MOR mRNA level and MOR expression in ACC were assayed by Reverse Transcription Polymerase Chain Reaction (RT-PCR) and western blot. Results: We found that intra-ACC administration of morphine induced significant antinociceptive effects in a dose-dependent manner in rats with inflammatory pain. Furthermore, the antinociceptive effects induced by morphine were attenuated by intra-ACC injection of the opioid receptor antagonist naloxone, indicating an involvement of opioid receptor in nociceptive modulation in ACC in rats with inflammatory pain. Moreover, intra-ACC administration of the MOR antagonist β-funaltrexamine (β-FNA) attenuated the morphine-induced antinociception significantly in rats with inflammatory pain. The results demonstrated that blockade MOR by β-FNA inhibited the morphine-induced antinociception, indicating that MOR plays an important role in nociceptive modulation in ACC in rats with inflammatory pain. We further found that the morphine-induced antinociception was lower in rats with inflammatory pain than that in normal rats. Interestingly, we found that there were significant decreases in MOR mRNA level and MOR expression in ACC in rats with inflammatory pain compared with intact rats tested by RT-PCR and western blot, indicating that there is a down regulation in MOR expression in rats with inflammatory pain, which support our above results that morphine-induced antinociception was lower in rats with inflammatory pain than that in normal rats. Conclusion: These findings suggest that MOR plays an important role in nociceptive modulation in ACC in rats with inflammatory pain and there is a down-regulation in MOR expression in rats with inflammatory pain.

Role of Mu-Opioid Receptor in Nociceptive Modulation in the Anterior Cingulate Cortex of Rats with Inflammatory Pain

Role of Mu-Opioid Receptor in Nociceptive Modulation in the Anterior Cingulate Cortex of Rats with Inflammatory Pain

In Vivo Multimodal Magnetic Resonance Imaging Changes After N-Methyl-d-Aspartate-Triggered Spasms in Infant Rats.

Despite the serious neurodevelopmental sequelae of epileptic encephalopathy during infancy, the pathomechanisms involved remain unclear. To find potential biomarkers that can reflect the pathogenesis of epileptic encephalopathy, we explored the neurometabolic and microstructural sequelae after infantile spasms using a rat model of infantile spasms and in vivo magnetic resonance imaging techniques. Rats prenatally exposed to betamethasone were subjected to three rounds of intraperitoneal N-methyl-d-aspartate (NMDA) triggering of spasms or received saline injections (controls) on postnatal days (P) 12, 13, and 15. Chemical exchange saturation transfer imaging of glutamate (GluCEST) were performed at P15 and 22 and diffusion tensor imaging and additional spectroscopy (1H-MRI/MRS) of the cingulate cortex were serially done at P16, 23, and 30 and analyzed. Pathological analysis and western blotting were performed with rats sacrificed on P35. Within 24 h of the three rounds of NMDA-induced spasms, there was an acute increase in the GluCEST (%) in the cortex, hippocampus, and striatum. When focused on the cingulate cortex, mean diffusivity (MD) was significantly decreased during the acute period after multiple spasms with an increase in γ-aminobutyric acid (GABA), glutamate, and glutamine N-acetylaspartate-plus-N-acetylaspartylglutamate (tNAA), total choline, and total creatine. The juvenile rats also showed decreased MD on diffusion tensor imaging and significant decreases in taurine, tNAA, and macromolecules-plus-lipids in the cingulate cortex. Pathologically, there was a significant reduction in glial fibrillary acidic protein, myelin basic protein, and neuronal nuclei expression in the cingulate cortex of rats with NMDA-induced spasms. These neurometabolic and microstructural alterations after NMDA-triggered spasms might be potential imaging biomarkers of epileptic encephalopathy.

Changes of Doublecortin-Immunoreactive Cells from the Acute Phase to Chronic Phase After Transient Global Brain Ischemia in Rat Cingulate Cortex.

Doublecortin (DCX)-immunoreactive (-ir) cells play important roles in adult cortical remodeling. We previously reported that DCX-ir cells decrease after transient global brain ischemia (GBI) in the cingulate cortex (Cg) of rats. In the present study, we examined the changes of DCX-ir cells from the acute to the chronic phase after GBI in rats. Transient GBI was induced by a four-vessel occlusion model as described previously. Thirty-six rats were divided into six groups: day 7 after sham operation (Group Sham+A), day 7 after 3 min GBI (Group GBI3+A), day 7 after 10 min GBI (Group GBI10+A), day 90 after sham operation (Group Sham+C), day 90 after 3 min GBI (Group GBI3+C), and day 90 after 10 min GBI (Group GBI10+C). The numbers of DCX-ir cells per unit area (mm2) were investigated in the anterior cingulate cortex (ACC) and retrosplenial cortex (RS). A two-way factorial analysis of variance regarding the time of GBI (sham, GBI3, GBI10) or the period after GBI (day 7, day 90) was employed in each area. Regarding the time of GBI, there were significant differences in both the ACC and the RS (p<0.001, respectively). Regarding the period after GBI, there was no significant difference in the ACC, whereas a significant difference was found in the RS (p=0.005). In each area and in each phase, the numbers did not change in GBI3 (one-way ANOVA followed by a Tukey test) and decreased in GBI10 (p<0.005). The numbers in the RS from the acute phase to chronic phase did not change in the sham and GBI3, and decreased in GBI10 (independent t-test, p<0.001). However, histochemical staining with Fluoro-Jade B suggested that neuronal cell death did not occur in both the ACC and the RS in all groups. The present findings indicate that the cortical remodeling potential in the Cg decreases in the acute phase after GBI, and continues to decrease until the chronic phase.

Effect of Nutmeg Administration on the Anterior Cingulate Cortex (Area 24a) of Adult Male Albino Rats and the Protective Role of Vitamin C: A Histological and Immunohistochemical Study

Effect of Nutmeg Administration on the Anterior Cingulate Cortex (Area 24a) of Adult Male Albino Rats and the Protective Role of Vitamin C: A Histological and Immunohistochemical Study

Effect of Nutmeg Administration on the Anterior Cingulate Cortex (Area 24a) of Adult Male Albino Rats and the Protective Role of Vitamin C: A Histological and Immunohistochemical Study

Effect of Nutmeg Administration on the Anterior Cingulate Cortex (Area 24a) of Adult Male Albino Rats and the Protective Role of Vitamin C: A Histological and Immunohistochemical Study

Mechanical Stimulus-Induced Wthdrawal Behavior Increases Subsequent Pre-Stimulus Local Field Potential Power in the Rostral Anterior Cingulate Cortex in Unanesthetized Rats.

BackgroundThe rostral anterior cingulate cortex (rACC) is important in pain expectation. Previous studies demonstrated that mechanical stimulus-induced withdrawal behaviors are spinally-mediated nocifensive reflexes in rats, but it is not known whether pain expectation is influenced by withdrawal behaviors.Material/MethodsWe reanalyzed previous mechanosensitivity measurements of 244 rats measured 5 times in succession. To study neural oscillation in the rACC, 1 recording microwire array was surgically implanted. Then, we simultaneously recorded the local field potential (LFP) of the rACC over the course of multiple withdrawal behaviors in unanesthetized rats.ResultsFrom our previous withdrawal behavioral data in 244 rats, we observed that the distributions of paw withdrawal thresholds (PWTs) were denser and more concentrated after the first withdrawal behavior. Compared to the first mechanical stimulus, increased neuronal synchrony and a stronger delta band component existed in each pre-stimulus LFP in the rACC during subsequent stimuli.ConclusionsPain expectation could be involved in withdrawal behaviors, which is related to increased total power and delta band power of the subsequent pre-stimulus LFPs in the rACC.

Antinociception induced by galanin in anterior cingulate cortex in rats with acute inflammation

The present study was performed to explore the role of galanin in nociceptive modulation in anterior cingulate cortex (ACC) of rats with acute inflammation, and the changes in galanin and galanin receptor 2 (Gal R2) expressions in rats with acute inflammation. Intra-ACC injection of galanin induced antinociception in rats with acute inflammation, the antinociceptive effects induced by galanin were attenuated significantly by intra-ACC injection of the Gal R2 antagonist M871, indicating an involvement of Gal R2 in nociceptive modulation in ACC in rats with acute inflammation. Furthermore, we found that both the galanin mRNA expression and galanin content increased significantly in ACC in rats with acute inflammation than that in normal rats. Moreover, both the mRNA levels of Gal R2 and the content of Gal R2 in ACC increased significantly in rats with acute inflammation than that in normal rats. These results demonstrated that galanin induced antinociception in ACC in rats with acute inflammation. And there were changes in the expression of galanin and Gal R2 in rats with acute inflammation.

Effects of Neto1-siRNA on conditioned avoidance behavior and expression of NMDA receptor subunits in anterior cingulate cortex in rats with pain

Objective To evaluate the effects of Neto1-siRNA on pain-related negative affection and expression of Neto1 (Neuropilin and tolloid-like 1) and NMDA (N-methyl-D-aspartate) receptor NR2A and NR2B subunits in anterior cingulate cortex (ACC) in neuropathic pain (NP) model rats. Methods 40 healthy male Wistar rats were randomly divided into sham operated group (SO group, n=10) and chronic constriction injury of the sciatic nerve group(CCI group, n=10). Twenty-four days after injury LV-Neto1-RNAi (30160-1) was injected in ACC in rats of SO group and CCI group by stereotaxic apparatus to prepare siRNA SO group(n=10) and siRNA CCI group(n=10). The CCI model was established by the chronic constriction injury of the sciatic nerve. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of each groups were measured on 7th, 14th, 21th and 28th day after operation. The expression of Neto1, NR2A and NR2B subunit mRNA and protein in ACC by RT-PCR and Western Blotting respectively. Results Compared with SO group, TWL and MWT in CCI group were both decreased (P 0.05). In RT-PCR, expression of Neto1, NR2A and NR2B in CCI group was increased compared with SO group (P<0.05), and expression of Neto1 and NR2A was both decreased by Neto1-siRNA (P<0.05), while there was no difference of NR2B. In Western Blotting, expression of Neto1, NR2A and NR2B in CCI group was increased compared with SO group (P<0.05), and expression of Neto1 and NR2A was both decreased by Neto1-siRNA (P<0.05), while there was no difference of NR2B. Conclusion Decreased-expression of Neto1 in ACC may down-regulate NMDA receptor NR2A subunit in NP rats and does not affect pain-related negative affection. Key words: Pain; Anterior cingulate cortex; Conditioned avoidance behavior; Neuropilin and tolloid-like1 Protein; N-methyl-D-aspartate receptor

Electroacupuncture alleviates retrieval of pain memory and its effect on phosphorylation of cAMP response element-binding protein in anterior cingulate cortex in rats.

BackgroundRecent evidence suggests that persistent pain and recurrent pain are due to the pain memory which is related to the phosphorylation of cAMP response element-binding protein (p-CREB) in anterior cingulate cortex (ACC). Eletroacupuncture (EA), as a complementary Chinese medical procedure, has a significant impact on the treatment of pain and is now considered as a mind-body therapy.MethodsThe rat model of pain memory was induced by two injections of carrageenan into the paws, which was administered separately by a 14-day interval, and treated with EA therapy. The paw withdrawal thresholds (PWTs) of animals were measured and p-CREB expressions in ACC were detected by using immunofluorescence (IF) and electrophoretic mobility shift assay (EMSA). Statistical comparisons among different groups were made by one-way, repeated-measures analysis of variance (ANOVA).ResultsThe second injection of carrageenan caused the decrease of PWTs in the non-injected hind paw. EA stimulation applied prior to the second injection, increased the values of PWTs. In ACC, the numbers of p-CREB positive cells were significantly increased in pain memory model rats, which were significantly reduced by EA. EMSA results showed EA also down-regulated the combining capacity of p-CREB with its DNA. Furthermore, the co-expression of p-CREB with GFAP, OX-42, or NeuN in ACC was strengthened in the pain memory model rats. EA inhibited the co-expression of p-CREB with GFAP or OX-42, but not NeuN in ACC.ConclusionsThe present results suggest the retrieval of pain memory could be alleviated by the pre-treatment of EA, which is at least partially attributed to the down-regulated expression and combining capacity of p-CREB and the decreased expression of p-CREB in astrocytes and microglia cells.

Decision-making deficits associated with disrupted synchronization between basolateral amygdala and anterior cingulate cortex in rats after tooth loss.

Human studies have shown that multiple teeth loss was significantly associated with cognitive impairment, dementia and Alzheimer's disease. However, the causal relationship between tooth loss and cognitive deficits has not been clarified. Rodents demonstrate human-like cognitive faculties. In this study by performing rat gambling task (RGT), we reported that prolonged tooth loss condition by extracting all left molars in the rats led to an increase in the proportion of poor decision-makers, and decrease in the proportion of good decision-makers compared with controls. No influence was detected on the general activity and motivation after tooth loss. Recent experiments have shown that decision-making performances in the RGT rely on the functional integrity of the amygdala and anterior cingulate cortex (ACC). The theta band brain oscillation has been acknowledged for extensive cognitive functions. Here, we performed multiple-electrode array recordings of local field potential (LFP) in anesthetized rats. The results exhibited an increase in accumulative power of the theta frequency of LFP in the basolateral amygdala (BLA) and decrease of theta power in the ACC in tooth loss rats. Furthermore, cross-correlation analysis displayed that tooth loss suppressed the synchronization of theta frequency of LFP between the BLA and ACC, indicating reduced neuronal communications between these two regions. In conclusion, we demonstrate for the first time that tooth loss leads to higher-order cognitive deficits accompanied by the alteration of theta frequency of LFP in brain circuitries and disruption of neural network integrity.

Peripheral administration of a μ-opioid receptor agonist DAMGO suppresses the anxiolytic and stimulatory effects of caffeine.

We studied the possibility of modulation of the stimulatory and anxiolytic effects of caffeine by activation of μ-opioid receptors in the gastrointestinal tract. Caffeine in a dose of 10 mg/kg (but not in a dose of 100 mg/kg) had a strong anxiolytic and psychostimulant effect. This effect was manifested in a significant increase in the time spent in the open arms of the elevated plus-maze, elevation of locomotor activity, and stimulation of metabolism. Administration of DAMGO to animals receiving caffeine in a dose of 10 mg/kg abolished the anxiolytic and psychostimulant effects of caffeine. By contrast, administration of DAMGO to rats receiving caffeine in a dose of 100 mg/kg had the anxiolytic effect. Activation of peripheral μ-opioid receptors is followed by the inhibition of the central μ-opioid system. We observed a decrease in the number of μ-opioid receptors in the midbrain and cerebral cortex and inhibition of β-endorphin release from nerve ending of the cingulate cortex in rats. These changes are probably followed by activation of the adenosine system in the brain. Caffeine dose should be increased to achieve the effect. Therefore, the anxiolytic and stimulatory effects of caffeine in a dose of 10 mg/kg are abolished under these conditions. By contrast, the anxiolytic effect of caffeine in a dose of 100 mg/kg (not observed under normal conditions) develops after this treatment.

Transgenerational sex-specific impact of preconception stress on the development of dendritic spines and dendritic length in the medial prefrontal cortex.

Perinatal adverse experience programs social and emotional behavioral traits and is a major risk factor for the development of behavioral and psychiatric disorders. Little information is available on how adversity to the mother prior to her first pregnancy (preconception stress, PCS) may affect brain structural development, which may underlie behavioral dysfunction in the offspring. Moreover, little is known about possible sex-dependent consequences of PCS in the offspring. This study examined spine number/densityand dendritic length/complexity of layer II/III pyramidal neurons in the anterior cingulate (ACd), prelimbic/infralimbic (PL/IL) and orbitofrontal cortex (OFC) of male and female rats born to mothers exposed to unpredictable variable stress at different time points prior to reproduction. Our main findings are that in line with our hypothesis adversity to the mother before her pregnancy results in highly complex changes in neuronal morphology in the medial prefrontal, but not in the orbitofrontal cortical regions of her future offspring that persist into adulthood. Moreover, our study revealed that (1) in the PCS2 group (offspring of dams mated two weeks after stress) spine numbers and dendritic length and complexity were increased in response to PCS in the ACd and PL/IL, (2) these regional effects depended on the temporal proximity of adversity and conception, (3) in the ACd of the PCS2 group only males and the left hemispheres were affected. We speculate that these transgenerational brain structural changes are mediated by stress-induced epigenetic (re)programming of future gene activity in the oocyte.