Changes at cholecystokinin receptors induced by long-term treatment with diazepam and haloperidol

The unappreciated roles of the cholecystokinin receptor CCK(1) in brain functioning

The CCK(1) receptor is a G-protein-coupled receptor activated by the sulfated forms of cholecystokinin (CCK), a gastrin-like peptide released in the gastrointestinal tract and mammal brain. A substantial body of research supports the hypothesis that CCK(1)r stimulates gallbladder contraction and pancreatic secretion in the gut, as well as satiety in brain. However, this receptor may also fulfill relevant roles in behavior, thanks to its widespread distribution in the brain. The strategic location of CCK(1)r in mesolimbic structures and specific hypothalamic and brainstem nuclei lead to complex interactions with neurotransmitters like dopamine, serotonin, and glutamate, as well as hypothalamic hormones and neuropeptides. The activity of CCK(1)r maintains adequate levels of dopamine and regulates the activity of serotonin neurons of raphe nuclei, which makes CCK(1)r an interesting therapeutic target for the development of adjuvant treatments for schizophrenia, drug addiction, and mood disorders. Unexplored functions of CCK(1)r, like the transmission of interoceptive sensitivity in addition to the regulation of hypothalamic hormones and neurotransmitters affecting emotional states, well-being, and attachment behaviors, may open exciting roads of research. The absence of specific ligands for the CCK(1) receptor has complicated the study of its distribution in brain so that research about its impact on behavior has been published sporadically over the last 30 years. The present review reunites all this body of evidence in a comprehensive way to summarize our knowledge about the actual role of CCK in the neurobiology of mental illness.

The role of cholecystokinin in the induction of aggressive behavior: a focus on the available experimental data (review)

Cholecystokinin (CCK) is a neuropeptide that is (among others) reportedly involved in the pathophysiology of psychiatric disorders. The excitatory role of CCK in negative affective emotions as well as in aversive reactions, antisocial behaviors and memories, has been indicated by numerous electrophysiological, neurochemical and behavioral methodologies on both animal models for anxiety and human studies. The current review article summarizes the existing experimental evidence with regards to the role of CCK in the induction of aggressive behavior, and: (a) synopsizes the anatomical circuits through which it could potentially mediate all types of aggressive behavior, as well as (b) highlights the potential use of these experimental evidence in the current research quest for the clinical treatment of mood and anxiety disorders.

Effects of diazepam on125I-iomazenil-benzodiazepine receptor binding and epileptic seizures in the El mouse

OBJECTIVE

To investigate changes in free benzodiazepine receptor density in response to repeated, long-term administration of diazepam in epilepsy, we assessed 125I-iomazenil (125I-IMZ) binding in a mouse model.

METHODS

El mice were divided into two groups of 12 mice each which received either no diazepam (E1(D[-]) group) or 2 mg/kg of diazepam per week (El(D[+]) group). Nine ddY mice were used as a control. Once each week from the age of 5 to 19 weeks, the El mice received stimulation to produce epileptic seizures 20 minutes after receiving intraperitoneal injections. At 20 weeks of age, a total dose of 0.37 MBq of 125I-IMZ was injected in all mice and their brains were rapidly removed 3 hours later. The incidence of epileptic seizures at the age of 19 weeks and the autoradiograms of the brain were compared.

RESULTS

The incidence of epileptic seizures in response to weekly stimulation was significantly lower in the E1(D[+]) group than in the E1(D[-]) group (p < 0.001). The percent injected doses of 125I-IMZ per gram of tissue in the cortex, hippocampus and amygdala were significantly lower in the E1(D[+]) group than in the E1(D[-]) group (p < 0.05).

CONCLUSION

The results suggest that diazepam binds competitively to 125I-IMZ as an agonist to free benzodiazepine receptor sites in the cortex, hippocampus and amygdala and shows anticonvulsant effect in E1 mice.

Brain structures and neurotransmitters regulating aggression in cats: implications for human aggression

1. Violence and aggression are major public health problems. 2. The authors have used techniques of electrical brain stimulation, anatomical-immunohistochemical techniques, and behavioral pharmacology to investigate the neural systems and circuits underlying aggressive behavior in the cat. 3. The medial hypothalamus and midbrain periaqueductal gray are the most important structures mediating defensive rage behavior, and the perifornical lateral hypothalamus clearly mediates predatory attack behavior. The hippocampus, amygdala, bed nucleus of the stria terminalis, septal area, cingulate gyrus, and prefrontal cortex project to these structures directly or indirectly and thus can modulate the intensity of attack and rage. 4. Evidence suggests that several neurotransmitters facilitate defensive rage within the PAG and medial hypothalamus, including glutamate, Substance P, and cholecystokinin, and that opioid peptides suppress it; these effects usually depend on the subtype of receptor that is activated. 5. A key recent discovery was a GABAergic projection that may underlie the often-observed reciprocally inhibitory relationship between these two forms of aggression. 6. Recently, Substance P has come under scrutiny as a possible key neurotransmitter involved in defensive rage, and the mechanism by which it plays a role in aggression and rage is under investigation. 7. It is hoped that this line of research will provide a better understanding of the neural mechanisms and substrates regulating aggression and rage and thus establish a rational basis for treatment of disorders associated with these forms of aggression.

Opposite effects mediated by CCKA and CCKB receptors in behavioural and hormonal studies in rats

We compared the influence of two cholecystokinin (CCK) antagonists, devazepide and L-365,260 [3R-(+)-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepine-3y l)-N'-(3-methyl-phenyl)urea], upon two distinct phenomena, behavioural and hormonal effects of caerulein (5 micrograms/kg s.c.), and unselective CCK agonist, in rats. Behavioural effects were assessed in the elevated plus-maze and open field tests. In separate experiments, effects on thyrotropin (TSH), prolactin (PRL) and growth hormone (GH) levels in serum of male rats were studied. Caerulein inhibited the exploratory behaviour in the plus-maze. Time spent in the open part, the number of line crossings and closed arm entries were significantly decreased, whereas the ratio of failed attempts/closed arm entries was increased. The anti-exploratory effect of caerulein was antagonized by the pretreatment with L-365,260 (10 micrograms/kg), a preferential antagonist at CCKB receptors, but was increased by devazepide (1-100 micrograms/kg), a preferential CCKA antagonist. L-365,260 (1-100 micrograms/kg) and devazepide (1-100 micrograms/kg) given alone did not change the behaviour of rats in the plus-maze test. Caerulein (5 micrograms/kg) itself did not modify the locomotor activity of rats in open field. However, the concomitant administration of caerulein with devazepide (1-10 micrograms/kg) reduced the frequency of line crossings and rearings. In the hormonal studies caerulein significantly decreased the cold-induced increase of TSH levels in serum. GH and PRL levels were not markedly affected by caerulein.(ABSTRACT TRUNCATED AT 250 WORDS)