Sex difference in gene expressions of cholecystokinin (CCK) and CCK receptor in young and old rats

Cholecystokinin (CCK): a neuromodulator with therapeutic potential in Alzheimer's and Parkinson's disease

Cholecystokinin (CCK) is a neuropeptide modulating digestion, glucose levels, neurotransmitters and memory. Recent studies suggest that CCK exhibits neuroprotective effects in Alzheimer's disease (AD) and Parkinson's disease (PD). Thus, we review the physiological function and therapeutic potential of CCK. The neuropeptide facilitates hippocampal glutamate release and gates GABAergic basket cell activity, which improves declarative memory acquisition, but inhibits consolidation. Cortical CCK alters recognition memory and enhances audio-visual processing. By stimulating CCK-1 receptors (CCK-1Rs), sulphated CCK-8 elicits dopamine release in the substantia nigra and striatum. In the mesolimbic pathway, CCK release is triggered by dopamine and terminates reward responses via CCK-2Rs. Importantly, activation of hippocampal and nigral CCK-2Rs is neuroprotective by evoking AMPK activation, expression of mitochondrial fusion modulators and autophagy. Other benefits include vagus nerve/CCK-1R-mediated expression of brain-derived neurotrophic factor, intestinal protection and suppression of inflammation. We also discuss caveats and the therapeutic combination of CCK with other peptide hormones.

Cholecystokinin B receptor gene polymorphism (rs2941026) is associated with anxious personality and suicidal thoughts in a longitudinal study

OBJECTIVES

Cholecystokinin is a neuropeptide with a role in the neurobiology of adaptive behaviour that is implicated in anxiety disorders, while the underlying mechanisms currently remain insufficiently explained. The rs2941026 variation in the cholecystokinin B receptor gene has previously been associated with trait anxiety. Our aim was to investigate associations between the CCK_B receptor gene polymorphism rs2941026 with anxiety, personality, depressiveness and suicidality in a longitudinal study of late adolescence and early adulthood.

METHODS

We used reports on trait and state anxiety, depressiveness and suicidal thoughts, as well as Affective Neuroscience Personality Scales, from the two birth cohorts of the Estonian Children Personality, Behaviour and Health Study. We measured associations between the CCKBR gene rs2941026 and anxiety-related phenotypes both longitudinally and cross-sectionally at ages 15, 18, 25 and 33.

RESULTS

Homozygosity for both alleles of the CCKBR rs2941026 was associated with higher trait and state anxiety in the longitudinal analysis. Cross-sectional comparisons were statistically significant at ages 18 and 25 for trait anxiety and at ages 25 and 33 for state anxiety. Higher depressiveness and suicidal thoughts were associated with the A/A genotype at age 18. Additionally, homozygosity for the A-allele was related to higher FEAR and SADNESS in the Affective Neuroscience Personality Scales. The genotype effects were more apparent in females, who displayed higher levels of negative affect overall.

CONCLUSIONS

CCKBR genotype is persistently associated with negative affect in adolescence and young adulthood. The association of the CCKBR rs2941026 genotype with anxiety-related phenotypes is more pronounced in females.

Cholecystokinin-8 activates myenteric neurons in 21- and 35-day old but not 4- and 14-day old rats

Cholecystokinin (CCK) activates the myenteric neurons of adult rats. The goal of this work is to determine the ontogeny of this activation by CCK-8 in the myenteric plexus of the duodenum (2cm immediately following the pyloric sphincter aborally) and compare it with that of the dorsal vagal complex (DVC) - which occurs in 1-day old pups. Despite the existence of both of the CCK receptors, CCK(1) and CCK(2), in 4, 14, 21 and 35 day old rats, CCK-8 (0, 5, 10, 20 and 40μg/kg, i.p.) increased Fos-like immunoreactivity (Fos-LI, a marker for neuronal activation) in the myenteric neurons of 21- and 35-day old rats but in the DVC of all age groups. As such, this belated activation of myenteric neurons by CCK-8 compared to the DVC may reflect a delayed role for these neurons in CCK-related functions.

Soya-bean agglutinin induced both direct and cholecystokinin-mediated pancreatic enzyme synthesis in rats

This study was conducted to examine the relationship between soya-bean agglutinin and cholecystokinin in stimulating pancreatic enzyme synthesis in rats. In experiment 1, 30 rats were given daily gastric infusions of 0, 3·5, 7·0, 10·5, or 14·0 mg of soya-bean agglutinin (no.=6) for 14 days. Compared with the control group, soya-bean agglutinin reduced weight gains, enhanced absolute and relative dry pancreatic weights, elevated serum cholecystokinin levels, and stimulated cholecystokinin mRNA expression in the intestine (P<0·001). Pancreatic nucleic acid composition and the pancreatic activities of the enzymes amylase, trypsin and chymotrypsin all increased in response to increasing levels of soya-bean agglutinin (P<0·001). In experiment 2, duodenal cells obtained from two rats were incubated at 37°C with either saline, 100 μg/ml soya-bean agglutinin, or a mixture of 100 μg/ml soya-bean agglutinin and 10 mmol/m of the L-type, calcium channel antagonist verapamil. Soya-bean agglutinin stimulated cholecystokinin mRNA expression and cholecystokinin release from small intestinal mucosal cells, and the effect was attenuated by verapamil. In experiment 3, pancreatic acinar cells, obtained from three rats, were incubated at 37 °C with either saline, or cholecystokinin (100 fmol/ml) and soya-bean agglutinin (1000 fmol/ml), either alone or in combination. Amylase, trypsin, and chymotrypsin activities from both culture media and acini cells were stimulated by both the soya-bean agglutinin and the cholecystokinin treatments. Enzyme activities, when the two factors were incubated in combination, were intermediate to those obtained when the factors were incubated alone. This suggesting that soya-bean agglutinin may depress the action of cholecystokinin on pancreatic enzymatic activities. In summary, soya-bean agglutinin appears to stimulate pancreatic enzyme synthesis both directly and also through a cholecystokinin-mediated pathway.

Gene expressions of cholecystokinin (CCK) and CCK receptors, and its satiety effect in young and old male rats

Cholecystokinin (CCK), one of the first discovered gastrointestinal hormones, which stimulates pancreatic enzyme secretion and induces gallbladder contraction, is one of the most abundant neurotransmitter peptides in the brain and is implicated in satiety via CCK-A receptors. We compared the suppressive effect of central administration of CCK on food intake in young and old rats. The suppressive effect on food intake was enhanced in old rats. To examine the mechanism of this enhanced suppression, we measured the mRNA levels of CCK, CCK-A and CCK-B receptors in the cerebral cortex and the hypothalamus of young and old male rats. The mRNA level of CCK-A receptors in the hypothalamus decreased with age, whereas the mRNA levels of CCK-B receptors in the hypothalamus and cerebral cortex did not. The mRNA level of CCK in the cerebral cortex decreased significantly in old rats, although the decrease in the hypothalamus was not significant. Therefore, the enhanced sensitivity to CCK of old rats could not be explained by changes in gene expressions of CCK and CCK receptors. Moreover, the effects of aging on the gene expressions of CCK-A and CCK-B receptors were different.