Anna Fodor

Maternal neglect with reduced depressive-like behavior and blunted c-fos activation in Brattleboro mothers, the role of central vasopressin

Early mother-infant relationships exert important long-term effects in offspring and are disturbed by factors such as postpartum depression. We aimed to clarify if lack of vasopressin influences maternal behavior paralleled by the development of a depressive-like phenotype. We compared vasopressin-deficient Brattleboro mothers with heterozygous and homozygous normal ones. The following parameters were measured: maternal behavior (undisturbed and separation-induced); anxiety by the elevated plus maze; sucrose and saccharin preference and forced swim behavior. Underlying brain areas were examined by c-fos immunocytochemistry among rest and after swim-stress. In another group of rats, vasopressin 2 receptor agonist was used peripherally to exclude secondary changes due to diabetes insipidus. Results showed that vasopressin-deficient rats spend less time licking-grooming their pups through a centrally driven mechanism. There was no difference between genotypes during the pup retrieval test. Vasopressin-deficient mothers tended to explore more the open arms of the plus maze, showed more preference for sucrose and saccharin and struggled more in the forced swim test, suggesting that they act as less depressive. Under basal conditions, vasopressin-deficient mothers had more c-fos expression in the medial preoptic area, shell of nucleus accumbens, paraventricular nucleus of the hypothalamus and amygdala, but not in other structures. In these areas the swim-stress-induced activation was smaller. In conclusion, vasopressin-deficiency resulted in maternal neglect due to a central effect and was protective against depressive-like behavior probably as a consequence of reduced activation of some stress-related brain structures. The conflicting behavioral data underscores the need for more sex specific studies.

Behavioral effects of perinatal opioid exposure.

Opioids are among the worlds oldest known drugs used mostly for pain relief, but recreational use is also widespread. A particularly important problem is opioid exposure in females, as their offspring can also be affected. Adverse intrauterine and postnatal environments can affect offspring development and may lead to various disabilities later in life. It is clear that repetitive painful experiences, such as randomly occurring invasive procedures during neonatal intensive care, can permanently alter neuronal and synaptic organization and therefore later behavior. At the same time, analgesic drugs can also be harmful, inducing neuronal apoptosis or withdrawal symptoms in the neonate and behavioral alterations in adulthood. Hence, risk-benefit ratios should be taken into consideration when pain relief is required during pregnancy or in neonates. Recreational use of opioids can also alter many aspects of life. Intrauterine opioid exposure has many toxic effects, inducing poor pregnancy outcomes due to underdevelopment, but it is believed that later negative consequences are more related to environmental factors such as a chaotic lifestyle and inadequate prenatal care. One of the crucial components is maternal care, which changes profoundly in addicted mothers. In substance-dependent mothers, pre- and postnatal care has special importance, and controlled treatment with a synthetic opioid (e.g., methadone) could be beneficial. We aimed to summarize and compare human and rodent data, as it is important to close the gap between scientific knowledge and societal policies. Special emphasis is given to gender differences in the sensitivity of offspring to perinatal opioid exposure.

The effects of vasopressin deficiency on aggression and impulsiveness in male and female rats

The role of vasopressin in aggression received much attention in recent years. However, vasopressin has complex roles on social behavior, which are affected by social experience, motivation and hormonal background, suggesting that its effects depend on the condition of subjects. This hypothesis was tested here by studying the impact of vasopressin deficiency on aggressiveness in reproductively naive and reproductively experienced males, as well as in lactating females, with special reference to the patterns and contexts of attack behavior. We also studied effects on impulsiveness, a behavioral feature strongly related to aggression. Vasopressin deficiency did not affect aggressiveness in reproductively experienced males, decreased the share of violent attacks in reproductively inexperienced males without affecting total attack counts, and suppressed maternal aggression in both early and late phases of lactation; violent forms of attack were decreased in the latter but not the former phase. Changes in aggression appeared unrelated to general changes in maternal behaviors. Impulsivity in the delay discounting task was markedly decreased by vasopressin deficiency in lactating females but not males. Taken together, our findings confirm that vasopressin has an impact on aggressiveness, but show that this impact depends on the condition of subjects, and suggest that the effects of vasopressin on maternal aggression develop in conjunction with impulsivity. Interestingly, overall effects on aggression and specific effects on violent attacks dissociated in both males and females, which hints to the possibility that vasopressin has distinct roles in the development of escalated forms of aggression.

Restoration of peripheral V2 receptor vasopressin signaling fails to correct behavioral changes in Brattleboro rats.

Beside its hormonal function in salt and water homeostasis, vasopressin released into distinct brain areas plays a crucial role in stress-related behavior resulting in the enhancement of an anxious/depressive-like state. We aimed to investigate whether correction of the peripheral symptoms of congenital absence of AVP also corrects the behavioral alterations in AVP-deficient Brattleboro rats. Wild type (WT) and vasopressin-deficient (KO) male Brattleboro rats were tested. Half of the KO animals were treated by desmopressin (V2-receptor agonist) via osmotic minipump (subcutaneous) to eliminate the peripheral symptoms of vasopressin-deficiency. Anxiety was studied by elevated plus maze (EPM), defensive withdrawal (DW) and marble burying (MB) tests, while depressive-like changes were monitored in forced swimming (FS) and anhedonia by sucrose preference test. Cell activity was examined in septum and amygdala by c-Fos immunohistochemistry after 10 min FS. KO rats spent more time in the open arm of the EPM, spent less time at the periphery of DW and showed less burying behavior in MB suggesting a reduced anxiety state. KO animals showed less floating behavior during FS revealing a less depressive phenotype. Desmopressin treatment compensated the peripheral effects of vasopressin-deficiency without a significant influence on the behavior. The FS-induced c-Fos immunoreactivity in the medial amygdala was different in WT and KO rats, with almost identical levels in KO and desmopressin treated animals. There were no differences in central and basolateral amygdala as well as in lateral septum. Our data confirmed the role of vasopressin in the development of affective disorders through central mechanisms. The involvement of the medial amygdala in the behavioral alterations of vasopressin deficient animals deserves further attention.

Depressive- and anxiety-like behaviors and stress-related neuronal activation in vasopressin-deficient female Brattleboro rats.

Vasopressin can contribute to the development of stress-related psychiatric disorders, anxiety and depression. Although these disturbances are more common in females, most of the preclinical studies have been done in males. We compared female vasopressin-deficient and +/+ Brattleboro rats. To test anxiety we used open-field, elevated plus maze (EPM), marble burying, novelty-induced hypophagia, and social avoidance tests. Object and social recognition were used to assess short term memory. To test depression-like behavior consumption of sweet solutions (sucrose and saccharin) and forced swim test (FST) were studied. The stress-hormone levels were followed by radioimmunoassay and underlying brain areas were studied by c-Fos immunohistochemistry. In the EPM the vasopressin-deficient females showed more entries towards the open arms and less stretch attend posture, drank more sweet fluids and struggled more (in FST) than the +/+ rats. The EPM-induced stress-hormone elevations were smaller in vasopressin-deficient females without basal as well as open-field and FST-induced genotype-differences. On most studied brain areas the resting c-Fos levels were higher in vasopressin-deficient rats, but the FST-induced elevations were smaller than in the +/+ ones. Similarly to males, female vasopressin-deficient animals presented diminished depression- and partly anxiety-like behavior with significant contribution of stress-hormones. In contrast to males, vasopressin deficiency in females had no effect on object and social memory, and stressor-induced c-Fos elevations were diminished only in females. Thus, vasopressin has similar effect on anxiety- and depression-like behavior in males and females, while only in females behavioral alterations are associated with reduced neuronal reactivity in several brain areas.

Possible contribution of epigenetic changes in the development of schizophrenia-like behavior in vasopressin-deficient Brattleboro rats.

Schizophrenia-like symptoms were detected in vasopressin-deficient (di/di) Brattleboro rats, and it was also suggested that schizophrenia might have an epigenetic component. We aimed to clarify if epigenetic changes contribute to schizophrenia-like behavior of this strain. Behavioral (locomotion by telemetry, cognition by novel object recognition, social recognition and social avoidance test, attention by pre-pulse inhibition) and epigenetic differences were compared between wild type and di/di animals. DNA methyltransferase1 (DNMT1), DNMT3a, as well as COMT, GAD, VGLUT1, 5HT2A, BDNF mRNA levels in prefrontal brain region and hippocampus were studied by qRT-PCR. Histone3 (H3) and H4 acetylation (Ac) were studied by western-blot followed by region specific examination of H3 lysine9 (K9) acetylation by immunohistochemistry. Impaired cognitive, social and attention behavior of di/di rats confirmed schizophrenia-like symptoms in our local colony. The pan-AcH3 immunoreactivity was lower in prefrontal region and elevated in the hippocampus of di/di animals. We found lower immunopositive cell number in the dorsal peduncular prefrontal cortex and the ventral lateral septum and increased AcH3K9 immunoreactivity in CA1 region of di/di animals. There were no major significant alterations in the studied mRNA levels. We confirmed that Brattleboro rat is a good preclinical model of schizophrenia. Its schizophrenia-like behavioral alteration was accompanied by changes in H3 acetylation in the prefrontal region and hippocampus. This may contribute to disturbances of many schizophrenia-related substances leading to development of schizophrenia-like symptoms. Our studies confirmed that not a single gene, rather fine changes in an array of molecules are responsible for the majority of schizophrenia cases.

Blunted HPA axis response in lactating, vasopressin-deficient Brattleboro rats.

Adaptation to stress is a basic phenomenon in mammalian life that is mandatorily associated with the activity of the hypothalamic-pituitary-adrenal (HPA) axis. An increased resting activity of the HPA axis can be measured during pregnancy and lactation, suggesting that these reproductive states lead to chronic load in females. In this study, we examined the consequences of the congenital lack of vasopressin on the activity of the HPA axis during lactation using vasopressin-deficient Brattleboro rats. Virgin and lactating, homozygous vasopressin-deficient rats were compared with control, heterozygous rats. In control dams compared with virgins, physiological changes similar to those observed in a chronic stress state (thymus involution, adrenal gland hyperplasia, elevation of proopiomelanocortin mRNA levels in the adenohypophysis, and resting plasma corticosterone levels) were observed. In vasopressin-deficient dams, adrenal gland hyperplasia and resting corticosterone level elevations were not observed. Corticotropin-releasing hormone (Crh) mRNA levels in the hypothalamic paraventricular nucleus were elevated in only the control dams, while oxytocin (OT) mRNA levels were higher in vasopressin-deficient virgins and lactation induced a further increase in both the genotypes. Suckling-induced ACTH and corticosterone level elevations were blunted in vasopressin-deficient dams. Anaphylactoid reaction (i.v. egg white) and insulin-induced hypoglycemia stimulated the HPA axis, which were blunted in lactating rats compared with the virgins and in vasopressin-deficient rats compared with the controls without interaction of the two factors. Vasopressin seems to contribute to the physiological changes observed during lactation mimicking a chronic stress state, but its role in acute HPA axis regulation during lactation seems to be similar to that observed in virgins. If vasopressin is congenitally absent, OT, but not the CRH, compensates for the missing vasopressin; however, the functional restitution remains incomplete.

The prepulse inhibition deficit appearance is largely independent on the circadian cycle, body weight, and the gender of vasopressin deficient brattleboro rat

Abstract Objective. A disturbance of sensorimotor gating measured by prepulse inhibition of acoustic startle (PPI) is one of the best tests of the schizophrenia-like behavior. Vasopressin was implicated in the development of schizophrenia; therefore, the naturally occurring vasopressin-deficient Brattleboro rat has been suggested to be a reliable non-pharmacological animal model. However, previous studies focusing on PPI deficit did not use proper control and despite clear gender differences in the development of the disorder, the effect of gender has been mostly neglected. Methods. First, we compared the „noise” and „tone” type prepulse at 73-77-81 dB intensity during the light or dark phase using small (~150 g) or big (~500 g) Wistar rats. The test parameters were validated by a pharmacological schizophrenia model (30 mg/kg ketamine i.p.). Than male, female, and lactating vasopressin-deficient animals were compared with +/+ ones. Results. We established that the prepulse “noise” type is not optimal for PPI testing. The cycle of the day as well as the body weight had no effect on PPI. Even if we compared vasopressin-deficient animals with their closely related +/+ controls, the PPI deficiency was visible with more pronounced effect at 77 dB prepulse intensity similarly to pharmacological schizophrenia model. Despite our expectation, the gender as well as lactation had no effect on the vasopressin-deficiency induced PPI deficit. Conclusions. The present data confirmed and extended our previous studies that vasopressin-deficient rat is a good model of schizophrenia. It seems that female as well as lactating Brattleboro rats are useful tools for testing putative novel antipsychotics in line with special attention required for schizophrenic women.

Enhanced innate fear and altered stress axis regulation in VGluT3 knockout mice

Abstract Glutamatergic neurons, characterized by vesicular glutamate transporters (VGluT1-3) provide the main excitation in the brain. Their disturbances have been linked to various brain disorders, which could be also modeled by the contextual fear test in rodents. We aimed to characterize the participation of VGluT3 in the development of contextual fear through its contribution to hypothalamic-pituitary-adrenocortical axis (HPA) regulation using knockout (KO) mice. Contextual fear conditioning was induced by foot shock and mice were examined 1 and 7 d later in the same environment comparing wild type with KO. Foot shock increased the immobility time without context specificity. Additionally, foot shock reduced open arm time in the elevated plus maze (EPM) test, and distance traveled in the open field (OF) test, representing the generalization of fear. Moreover, KO mice spent more time with freezing during the contextual fear test, less time in the open arm of the EPM, and traveled a smaller distance in the OF, with less entries into the central area. However, there was no foot shock and genotype interaction suggesting that VGluT3 does not influence the fear conditioning, rather determines anxiety-like characteristic of the mice. The resting hypothalamic CRH mRNA was higher in KO mice with reduced stressor-induced corticosterone elevations. Immunohistochemistry revealed the presence of VGluT3 positive fibers in the paraventricular nucleus of hypothalamus, but not on the hypophysis. As a summary, we confirmed the involvement of VGluT3 in innate fear, but not in the development of fear memory and generalization, with a significant contribution to HPA alterations. Highlights VGluT3 KO mice show innate fear without significant influence on fear memory and generalization. A putative background is the higher resting CRH mRNA level in their PVN and reduced stress-reactivity.