Berta Lasheras

Cognitive impairment associated to HPA axis hyperactivity after maternal separation in rats

Exposure to early stressful adverse life events may increase vulnerability to psychopathology in adult life. There are important memory disturbances in stress-related psychiatric disorders. Therefore, there is much interest in understanding the mechanisms responsible for interactions between stress and cognition. Male Wistar rats that experienced 3-h daily separations from the dam during the first 3 weeks of life (maternal separation, MS) showed in adulthood a depressive-like behaviour in the forced swimming test, increased hypothalamic-pituitary-adrenal (HPA) axis responsiveness to stressors and elevated CRF mRNA in the paraventricular nucleus of the hypothalamus (PVN). In the hippocampus of MS rats, there was a lower glucocorticoid receptor density. MS produced significant learning impairments both in the Morris water maze and in the novel object recognition test (NORT). The glucocorticoid receptor antagonist mifepristone and the beta-adrenoceptor antagonist propranolol were able to completely reverse the increased immobility time in the forced swimming test and the memory deficits in the NORT observed in MS rats. Our data support the hypothesis that elevated secretion of glucocorticoids may be associated to behavioural and cognitive deficits in MS rats. The stress hyperresponsiveness observed in MS rats could be attributed, at least in part, to an impaired feedback sensitivity mediated by hippocampal glucocorticoid receptors. It can also be suggested the possible involvement of the noradrenergic system in cognitive impairments mediated by glucocorticoids in the MS model.

Effects of neonatal stress on markers of synaptic plasticity in the hippocampus: implications for spatial memory.

Early stressful adverse situations may increase the vulnerability to cognitive deficits and psychiatric disorders, such as depression. Maternal separation (MS) has been used as an animal model to study changes in neurochemistry and behavior associated with exposure to early‐life stress. This study investigated the effects of neonatal stress (MS) on the expression of synaptic plasticity markers in the hippocampus and a purported relationship to cognitive processes. Spatial learning (Morris water maze) significantly increased the expression of total levels of the neural cell adhesion molecule (NCAM), as well as its three major isoforms (NCAM‐120, ‐140, and ‐180) both in the control and MS groups. Interestingly, these increases in NCAM expression after learning were lower in MS animals when compared with control rats. MS induced a significant decrease in total levels of NCAM, and specifically, in the NCAM‐140 isoform expression. In the hippocampus of MS rats there was a significant decrease in brain‐derived neurotrophic factor and synaptophysin mRNA densities. Cell proliferation, measured as BrdU‐positive cells, was also decreased in the dentate gyrus of MS rats. Altogether these results suggest that MS can alter normal brain development, providing a potential mechanism by which early environmental stressors may influence vulnerability to show cognitive impairments later in life.

Cholinergic-serotonergic imbalance contributes to cognitive and behavioral symptoms in Alzheimer's disease

Neuropsychiatric symptoms seen in Alzheimers disease (AD) are not simply a consequence of neurodegeneration, but probably result from differential neurotransmitter alterations, which some patients are more at risk of than others. Therefore, the hypothesis of this study is that an imbalance between the cholinergic and serotonergic systems is related to cognitive symptoms and psychological syndromes of dementia (BPSD) in patients with AD. Cholinergic and serotonergic functions were assessed in post-mortem frontal and temporal cortex from 22 AD patients who had been prospectively assessed with the Mini-Mental State examination (MMSE) for cognitive impairment and with the Present Behavioral Examination (PBE) for BPSD including aggressive behavior, overactivity, depression and psychosis. Not only cholinergic deficits, but also the cholinacetyltransferase/serotonin ratio significantly correlated with final MMSE score both in frontal and temporal cortex. In addition, decreases in cholinergic function correlated with the aggressive behavior factor, supporting a dual role for the cholinergic system in cognitive and non-cognitive disturbances associated to AD. The serotonergic system showed a significant correlation with overactivity and psychosis. The ratio of serotonin to acetylcholinesterase levels was also correlated with the psychotic factor at least in women. It is concluded that an imbalance between cholinergic-serotonergic systems may be responsible for the cognitive impairment associated to AD. Moreover, the major findings of this study are the relationships between neurochemical markers of both cholinergic and serotonergic systems and non-cognitive behavioral disturbances in patients with dementia.

Effects of maternal separation on hypothalamic–pituitary–adrenal responses, cognition and vulnerability to stress in adult female rats

We studied the long term effects of neonatal stress in female rats and subsequent responses to stress when adults. Female rats that experienced maternal separation (MS) showed in adulthood depressive-like behavior in the forced swimming test and cognitive impairments in the novel object recognition test, which were reverted by the glucocorticoid receptor antagonist mifepristone or the beta-adrenoceptor antagonist propranolol. Markers of HPA axis (corticosterone levels, CRF mRNA levels in the paraventricular nucleus and glucocorticoid receptor density in the hippocampus) were altered by MS, suggesting that an altered HPA axis function may be associated to behavioral and cognitive deficits in MS female rats. In addition, MS rats were found to be more vulnerable to chronic stress than controls as shown by decreases in open field activity, increases in immobility time in the forced swim test, and changes in markers of HPA axis (decreases in the density of glucocorticoid receptors). These present findings are discussed in terms of gender differences in adulthood.

Enhanced anxiety, depressive-like behaviour and impaired recognition memory in mice with reduced expression of the vesicular glutamate transporter 1 (VGLUT1)

Three isoforms of a vesicular glutamate transporter (VGLUT1–3) have been identified. Of these, VGLUT1 is the major isoform in the cerebral cortex and hippocampus where it is selectively located on synaptic vesicles of excitatory glutamatergic terminals. Variations in VGLUT1 expression levels have a major impact on the efficacy of glutamate synaptic transmission. Given evidence linking alterations in glutamate neurotransmission to various neuropsychiatric disorders, we investigated the possible influence of a down‐regulation of VGLUT1 transporter on anxiety, depressive‐like behaviour and learning. The behavioural phenotype of VGLUT1‐heterozygous mice (C57BL/6) was compared to wild‐type (WT) littermates. Moreover, VGLUT1–3 expression, hippocampal excitatory terminal ultrastructure and neurochemical phenotype were analysed. VGLUT1‐heterozygous mice displayed normal spontaneous locomotor activity, increased anxiety in the light–dark exploration test and depressive‐like behaviour in the forced swimming test: no differences were shown in the elevated plus‐maze model of anxiety. In the novel object recognition test, VGLUT1+/– mice showed normal short‐term but impaired long‐term memory. Spatial memory in the Morris water maze was unaffected. Western blot analysis confirmed that VGLUT1 heterozygotes expressed half the amount of transporter compared to WT. In addition, a reduction in the reserve pool of synaptic vesicles of hippocampal excitatory terminals and a 35–45% reduction in GABA in the frontal cortex and the hippocampus were observed in the mutant mice. These observations suggest that a VGLUT1‐mediated presynaptic alteration of the glutamatergic synapses, in specific brain regions, leads to a behavioural phenotype resembling certain aspects of psychiatric and cognitive disorders.

Differential involvement of 5-HT1B/1D and 5-HT6 receptors in cognitive and non-cognitive symptoms in Alzheimer's disease

Growing evidence suggests that a compromised serotonergic system plays an important role in the pathophysiology of Alzheimers disease (AD). We assessed the expression of 5-HT1B/1D and 5-HT6 receptors and cholinacetyltransferase (ChAT) activity in post-mortem frontal and temporal cortex from AD patients who had been prospectively assessed for cognitive function using the Mini-Mental State Examination (MMSE) and behavioral changes using the Present Behavioral Examination (PBE). 5-HT1B/1D and 5-HT6 receptor densities were significantly reduced in both cortical areas. 5-HT1B/1D receptor density was correlated to MMSE decline in the frontal cortex, supporting its implication in memory impairment. The best predictor for lowered 5-HT6 receptor density in the temporal cortex was the PBE measure of overactivity. The 5-HT6/ChAT ratio was related to aggression both in the frontal and temporal cortex. Therefore, antagonists acting at 5-HT6 receptors could be useful in the treatment of non-cognitive symptoms associated to AD.

Factors that Influence Under-Reporting of Suspected Adverse Drug Reactions among Community Pharmacists in a Spanish Region

Background: The spontaneous reporting system is the most efficient warning system of adverse drug reactions (ADRs). Pharmacists can play an important role in the detection and reporting of ADRs. The factors that affect under-reporting among these professionals are unknown in Spain.Objective: To identify the factors that influence community pharmacists’ ADR under-reporting in Navarra, a Northern Spanish region.Methods: A case-control study was conducted on a population of 802 community pharmacists working in Navarra. Cases were pharmacists who had reported at least two ADRs to the region’s drug surveillance unit between 2003 and 2005 and who agreed to participate in the study (18/20; 90%). A random sample of 60 controls was selected from the 762 pharmacists who had not reported any ADR during the same period of time.Results: Factors positively associated with ADR reporting were age, years of work experience as a pharmacist, participation in educational activities related to the detection and resolution of drug-related problems, the habit of detecting ADRs as part of pharmacists’ duties, having the basic knowledge needed to report ADRs, and disagreement with the common belief among healthcare professionals that ’to report an ADR it is necessary to be sure that the reaction is related to the use of a particular drug’. The most frequently mentioned reasons for not reporting ADRs were the ADR is not serious, the ADR is already known, uncertainty concerning the causal relationship between the ADR and the drug, forgetting to report the ADR and a lack of time.Conclusions: Pharmacists’ knowledge, beliefs, behaviour and motivation play an important role in ADR reporting. Under-reporting might be improved through activities focused on modifying such factors.

MDMA ('Ecstasy') enhances 5-HT1A receptor density and 8-OH-DPAT-induced hypothermia: blockade by drugs preventing 5-hydroxytryptamine depletion.

One week after a single administration of 3,4-methylenedioxymethamphetamine (MDMA HCI, 30 mg/kg i.p.), 5-HT1A receptor density was significantly increased by approximately 25-30% in the frontal cortex and hypothalamus of rats. The increased density correlated with the potentiation of the hypothermic response to the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 1 mg/kg s.c.). Hypothalamic 5-HT7 receptors, which also bind 8-OH-DPAT, were not changed, however, by MDMA. Fluoxetine (5 mg/kg s.c.), ketanserin (5 mg/kg s.c.) or haloperidol (2 mg/kg i.p.), given 15 min prior to MDMA, prevented the depletion of 5-hydroxytryptamine (5-HT) induced by MDMA and also blocked the effects of this neurotoxin on 5-HT1A receptor density and on 8-OH-DPAT-induced hypothermia. The protection afforded by drugs against 5-HT loss did not correlate, however, with the antagonism of the acute hyperthermic effect of MDMA. The present results indicate that drugs able to prevent or to attenuate MDMA-induced 5-HT loss also prevent the changes in 5-HT1A receptor density as well as the enhanced hypothermic response to the 5-HT1A receptor agonist 8-OH-DPAT in MDMA-treated rats.

Differential regulation by methylenedioxymethamphetamine of 5-hydroxytryptamine1A receptor density and mRNA expression in rat hippocampus, frontal cortex, and brainstem: the role of corticosteroids.

Abstract: The present study examined the effects of repeated administration to rats of 3,4‐methylenedioxymethamphetamine (MDMA, “Ecstasy”) on 5‐hydroxytryptamine1A (5‐HT1A) receptor density and mRNA expression in the hippocampus, frontal cortex, and brainstem. As expected, 7 days after subacute MDMA administration (20 mg/kg i.p. twice daily for 4 consecutive days) 5‐HT content was markedly reduced (−70%) in the hippocampus and the frontal cortex. 5‐HT1A receptor density was increased in the frontal cortex by 23% and decreased in the hippocampus and the brainstem by 25%. These changes correlated with an enhanced or diminished 5‐HT1A receptor mRNA expression in the three regions studied. To examine the influence of corticosteroids on these changes, adrenalectomized (ADX) rats received the same dosage regimen as above. Adrenalectomy by itself did not modify 5‐HT content in the brain regions examined and increased 5‐HT1A receptor density in the hippocampus (+20%) but produced no change in the frontal cortex and brainstem. Adrenalectomy also prevented MDMA‐induced changes in receptor number in the hippocampus and brainstem but not in the frontal cortex. Dexamethasone (1 mg/kg/day i.p.) administered for 7 consecutive days reversed the effects of adrenalectomy in the hippocampus but not in the frontal cortex. In the brainstem, MDMA no longer reduced 5‐HT1A receptor number in ADX rats, but a significant reduction was restored when ADX animals received the glucocorticoid treatment. The present data show that MDMA may affect 5‐HT1A receptors in a regionally dependent manner, notably through a drug effect on corticosterone release, which attenuates 5‐HT1A receptor gene transcription selectively in the hippocampus.

Neonatal stress affects vulnerability of cholinergic neurons and cognition in the rat: Involvement of the HPA axis

Adverse experiences early in life may sensitize specific neurocircuits to subsequent stressors. We have evaluated in maternal separation (MS) rats, an animal paradigm of early-life stress, the effects of a selective cholinergic lesion on cognitive function as well as susceptibility of cholinergic neurons to the lesion. MS rats subjected to a cholinergic lesion by administration of the immunotoxin 192 IgG-saporin, showed significant decreases in both choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity compared to control lesioned rats. Morris water maze results revealed a significant impairment in learning and memory function in MS adult rats and further cognitive deficits after the lesion. The lesion of cholinergic neurons induced a significant decrease in glucocorticoid receptor density in MS rats, accompanied by increases in CRF mRNA expression. Decreases in NGF and increases in NGF-p75NTR expression have also been found in MS rats. Our results suggest that vulnerability of basal forebrain cholinergic nerve cells might be affected by the HPA axis. The present data are discussed not only in terms of conditions that occur during ageing or Alzheimer disease, but also regarding a purported involvement of the cholinergic system in the regulation of HPA axis activity.