Financial difficulties but not other types of recent negative life events show strong interactions with 5-HTTLPR genotype in the development of depressive symptoms

Several studies indicate that 5-HTTLPR mediates the effect of childhood adversity in the development of depression, while results are contradictory for recent negative life events. For childhood adversity the interaction with genotype is strongest for sexual abuse, but not for other types of childhood maltreatment; however, possible interactions with specific recent life events have not been investigated separately. The aim of our study was to investigate the effect of four distinct types of recent life events in the development of depressive symptoms in a large community sample. Interaction between different types of recent life events measured by the List of Threatening Experiences and the 5-HTTLPR genotype on current depression measured by the depression subscale and additional items of the Brief Symptom Inventory was investigated in 2588 subjects in Manchester and Budapest. Only a nominal interaction was found between life events overall and 5-HTTLPR on depression, which failed to survive correction for multiple testing. However, subcategorising life events into four categories showed a robust interaction between financial difficulties and the 5-HTTLPR genotype, and a weaker interaction in the case of illness/injury. No interaction effect for the other two life event categories was present. We investigated a general non-representative sample in a cross-sectional approach. Depressive symptoms and life event evaluations were self-reported. The 5-HTTLPR polymorphism showed a differential interaction pattern with different types of recent life events, with the strongest interaction effects of financial difficulties on depressive symptoms. This specificity of interaction with only particular types of life events may help to explain previous contradictory findings

Deletion of the CCK2 receptor abolishes the development of hyperalgesia in mononeuropathic mice

Abstract: 15th International symposium on Regulatory Peptide

Cat odour induced anxiety in rodents: changes in expression of neuropeptide genes in brain structures

The effect of cat odour exposure was studied on the behaviour and neuropeptide gene expression in rodents. Exposure to the cat odour suppressed the exploratory activity of male Wistar rats in the elevated zero-maze. Treatment with morphine (1 mg/kg) increased the exploratory behaviour of rats in an unfamiliar environment. Previous exposure of animals to the cat odour completely abolished this stimulating action of morphine. Cat odour exposure induced a significant increase in the expression of Pomc1, Oprm1 and Cck genes in the brain structures related to anxiety and motivation. The similar study was also performed in female 129Sv/C57/Bl6 mice. The exposure of wild-type and homozygous CCK2 receptor deficient mice to the cat odour did not reveal substantial differences between the two genotypes. However, the following exposure of mice to the elevated plus-maze established differences as homozygous mice displayed increased exploratory activity in the plus-maze. The cat odour exposure significantly reduced exploratory activity only in homozygous mice. Together with the increased exploratory activity in homozygous mice the expression of Oprm1 gene was elevated in the frontal cortex and mesencephalon. Thus, the reduced anxiety of homozygous mice seems to be related to an increased tone of opioid system in the brain. The exposure of mice to cat odour did not change the gene expression in wild-type mice, whereas in homozygous animals a significantly increased expression of the Mc3r gene in the frontal cortex and temporal lobe, and the Pomc1 gene in the temporal lobe, mesencephalon and mesolimbic area was established. Therefore, it is likely that the increased function of melanocortin system is responsible for the anxiogenic effect of cat odour exposure in homozygous mice. In conclusion, the experiments conducted on rodents demonstrate that the cat odour exposure induced anxiety is accompanied by the compensatory changes in the activity of opioid and melanocortin systems

Targeted mutation of CCK2 receptor gene antagonises behavioural changes induced by social isolation in female, but not in male mice

Neuropeptide cholecystokinin (CCK) regulates the adaptation of rodents in the novel environment. In the present study we analysed the behavioural changes induced by the individual housing in mice, lacking CCK2 receptors. The wild-type (+/+) and homozygous (−/−) CCK2 receptor deficient mice of both gender were used throughout the study. The weight gain during the 21-day isolation period and changes in the locomotor activity following the social separation were measured. The elevated plus-maze and resident/intruder tests were also performed to test alterations in the emotional behaviour. Social isolation induced locomotor hyperactivity, reduced weight gain and increased aggressiveness in the wild-type (+/+) and homozygous (−/−) male mice. In the wild-type (+/+) female mice the significant reduction of exploratory activity in the plus-maze was evident. By contrast, in female mice, lacking CCK2 receptors, the exploration of the plus-maze was not significantly affected by the individual housing. This finding demonstrates that the social isolation does not cause anxiety-like state in the CCK2 receptor deficient mice. Moreover, the targeted invalidation of CCK2 receptors increased in male mice the affinity of dopamine D2 receptors in the sub-cortical structures, whereas in female mice the increased affinity of 5-hydroxytryptamine2 (5-HT2) receptors in the frontal cortex was established. The increased affinity of 5-HT2 receptors is probably the compensatory change to the lack of CCK2 receptors in female mice and probably reflects the reduced sensitivity of these animals to the anxiogenic manipulations. In conclusion, targeted mutation of CCK2 receptors selectively antagonised the behavioural changes induced by the individual housing in females, but not in male mice

CCK2 receptor deficient mice: Evidence for changes in anxiety

Abstract: 15th International Symposium on Regulatory Peptide

Altered renal morphology in transgenic mice with cholecystokinin overexpression

Although cholecystokinin is a regulatory peptide with a predominant role in the brain and the gastrointestinal tract, there is an increasing evidence for its role in the kidney. The aim of this study was to reveal morphological changes in the structure of kidney of mice with cholecystokinin overexpression by means of light, transmission and scanning electron microscope, and atomic force microscopy. Using immunohistochemistry the expression of important basement membrane proteins collagen IV, laminin and fibronectin, as well the distribution of cholecystokinin-8 in the renal structures was evaluated. The altered morphology of kidneys of mice with cholecystokinin overexpression was seen by all microscopic techniques used. The renal corpuscles were relatively small with narrow capsular lumen. The basement membranes of renal tubules were thickened and the epithelial cells were damaged, which was more pronounced for distal tubules. Characteristic feature was the increased number of vesicles seen throughout the epithelial cells of proximal and especially in distal tubules reflecting to the enhanced cellular degeneration. The relative expression of laminin but not collagen IV in the glomerular basement membrane was higher than in the tubular basement membranes. The content of fibronectin, in opposite, was higher in tubular membranes. Cholecystokinin-8 was clearly expressed in the glomeruli, in Bowman’s capsule, in proximal and distal tubules, and in collecting ducts. Ultrastructural studies showed irregularly thickened glomerular basement membranes to which elongated cytopodia of differently shaped podocytes were attached. As foot processes were often fused the number of filtration pores was decreased. In conclusion, cholecystokinin plays important role in renal structural formation and in functioning as different aspects of urine production in mice with cholecystokinin overexpression are affected-the uneven glomerular basement membrane thickening, structural changes in podocytes and in filtration slits affect glomerular filtration, while damaged tubular epithelial cells and changed composition of thickened tubular basement membranes affect reabsorption

Deletion of the CCK2 receptor gene reduces mechanical sensitivity and abolishes the development of hyperalgesia in mononeuropathic mice

Previous studies suggest that cholecystokinin (CCK) is implicated in the modulation of pain sensitivity and the development of neuropathic pain. We used CCK(2) receptor deficient (CCK(2) (-/-)) mice and assessed their mechanical sensitivity using Von Frey filaments, as well as the development and time course of mechanical hyperalgesia in a model of neuropathic pain. We found that CCK(2) (-/-) mice displayed mechanical hyposensitivity, which was reversed to the level of wild-type animals after administration of naloxone (0.1-10 mg/kg). On the other hand, injection of L-365260 (0.01-1 mg/kg), an antagonist of CCK(2) receptors, decreased dose-dependently, mechanical sensitivity in wild-type mice. The mechanism of reduced mechanical sensitivity in CCK(2) (-/-) mice may be explained by changes in interactions between CCK and opioid systems. Indeed, CCK(2) (-/-) mice natively expressed higher levels of lumbar CCK(1), opioid delta and kappa receptors. Next, we found that CCK(2) (-/-) mice did not develop mechanical hyperalgesia in the Bennett's neuropathic pain model. Induction of neuropathy resulted in decrease of lumbar pro-opiomelanocortin (POMC) gene expression in wild-type mice, but increase of POMC expression in CCK(2) (-/-) mice. In addition, induction of neuropathy resulted in further increase of opioid delta receptor in CCK(2) (-/-) mice. Gene expression results indicate up-regulation of opioid system in CCK(2) (-/-) mice, which apparently result in decreased neuropathy score. Our study suggests that not only pain sensitivity, but also mechanical sensitivity and the development of neuropathic pain are regulated by antagonistic interactions between CCK and opioid systems

P.3.070 CCK2 receptor deficient mice: Changes in anxiety and pain sensitivity

Poster session P.3. Anxiety disorder and anxiolyti

Altered pain sensitivity and morphine-induced anti-nociception in mice lacking CCK2 receptors

Rationale Cholecystokinin (CCK) interacts with the endopioid system in the regulation of various physiological functions, including the control of pain sensitivity, motor activity and emotional behaviour. Objective The aim of the present work was to study the pain sensitivity, morphine-induced antinociception and density of opioid receptors in mice lacking CCK2 receptors. Methods Plantar analgesia and hotplate tests were used to evaluate pain sensitivity and morphine-induced antinociception. The parameters of opioid receptors were analysed by using [3H]-diprenorphine binding. Results In the plantar analgesia test the latency of hind paw withdrawal was significantly increased in CCK2 receptor deficient mice compared to wild-type (+/+) littermates. The treatment with saline reversed the reduced pain sensitivity in heterozygous (+/−) and homozygous (−/−) mice. The administration of morphine (1 mg/kg) induced a significantly stronger antinociceptive effect in homozygous (−/−) mice compared with wild-type (+/+) animals. In the hotplate test, only homozygous (−/−) mutant mice displayed the delayed latency of hind paw licking/shaking in comparison with wild-type (+/+) mice. The injection of saline and isolation of mice for 30 min reversed the delayed response in homozygous (−/−) mice. However, in this test, the anti-nociceptive action of morphine (5–10 mg/kg) in mutant mice did not differ from that in wild-type (+/+) littermates. By contrast, the jump latency was decreased in both homozygous (−/−) and heterozygous (+/−) mice in the hotplate test. The increased density of opioid receptors was established in the striatum of homozygous (−/−) mice. Conclusion It is apparent that the targeted mutagenesis of the CCK2 receptor gene has different effects on the sensitivity of opioid receptors in various brain structures. This is a probable reason for the altered pain sensitivity and morphine-induced antinociception in mutant mice compared to wild-type (+/+) littermates