CCK-B, novel target.

[vecktor]

I'm bored with the constant discussion of dull minor tweaks to known drugs and the same old targets so I thought I would throw some different targets;

I might have mentioned this before in the context of panicogens,
The cholestokinin in particular the CNS receptor CCK-B is interesting, a lot of work was done on this target about a decade ago and I haven't seen a lot since.

to briefly summarize CCK-A is found in the digestive system CCK-B is mainly found in the CNS. All the CCK-B antagonists found so far are anxiolytic. Some CCK-B agonists are potent anxiety causing agents some of which have been tested in man and can produce panic attacks at miniscule doses (50 ug or cck4).
as well rats, what is very interesting is that some of these agonists are peptides which have no difficulty crossing the blood brain barrier (2)

Another subset of CCK-B agonists has an opposite effect it has been suggested that there are multiple binding sites on the CCK-B receptor, for simplicity CCK-B1 and CCK-B2, the agonists that cause panic and anxiety are supposedly active at the B1 site and those with the opposite effect are B2 agonists. BC 264 a peptide B2 agonist has shown effects comparable to amphetamine in terms of exploration and learning in rats.(3)

The other very interesting thing is that CCK-B is involved in morphine and logically therefore all opioid tolerance, CCK-B antagonists can reduce morphine tolerance in rats, this has been tested in man and was shown not to work when L-365,260 was given to chrnic pain patients using morphine suggesting perhaps that it cannot reverse established tolerance but that it might be able to prevent tolerance developing?


Does anyone know if any non peptide CCK-B2 agonists have been discovered, the antagonists are benzodiazepine type compounds IIRC. I would be interested to see any data on small molecule agonists of CCK-B.

its got to be more interesting than minor tweaks of methcathinone amphetamine and 4MAR.



http://www.ajp.psychiatryonline.org/cgi/content/abstract/152/8/1180

OBJECTIVE: The authors tested the prediction of temporal cortex activation during experimentally induced anxiety by using positron emission tomography and the [15O]H2O bolus-subtraction method to determine regional cerebral blood flow (CBF) changes in normal volunteers challenged with a bolus injection of cholecystokinin tetrapeptide (CCK4). METHOD: Eight right-handed healthy subjects (five male, three female; mean age, 26.4 years) underwent four 60-second [15O]H2O scans separated by 15-minute intervals; each scan followed an intravenous bolus injection of either saline (placebo) or CCK4 (50 micrograms). Each subject received CCK4 once, as the first or second bolus, in a random-order, placebo-controlled, double-blind fashion. Two of the three placebo conditions were nominally identical, and the remaining placebo was used to control for anticipatory anxiety. Magnetic resonance imaging scans were obtained for subsequent anatomical correlation of blood flow changes. RESULTS: CCK4, but not placebo, elicited a marked anxiogenic response, reflected by robust increases in subjective anxiety ratings and heart rate. CCK4-induced anxiety was associated with 1) robust and bilateral increases in extracerebral blood flow in the vicinity of the superficial temporal artery territory and 2) CBF increases in the anterior cingulate gyrus, the claustrum-insular-amygdala region, and the cerebellar vermis. CONCLUSIONS: Some of the temporopolar cortex CBF activation peaks previously reported in humans in association with drug- and non-drug- induced anxiety, as well as the increase in regional CBF in the claustrum-insular-amygdala region, may be of vascular and/or muscular origin.

Anxiety: Neurobiology, Clinic and Therapeutic Perspectives
By Michel Hamon,

http://books.google.co.uk/books?id=...ayET6XT&sig=FM0pRtPQlOJ3b--wETwfBTJZBkQ&hl=en



Neuropharmacology Volume 38, Issue 4, 1 April 1999, Pages 543-553

The effects of two selective CCKB agonists, BC 264 and BC 197, on memory processes were investigated in rats using a recently developed two-trial recognition memory task. Control animals showed recognition memory after a 2 but not a 6 h time interval between the two trials, thus allowing a memory impairing (2 h) or improving (6 h) effect of pharmacological treatments to be measured. Drugs were injected i.p. before the second trial (retrieval phase). This experimental procedure was first studied with scopolamine and DL-amphetamine, for which a significant deficit after a 2 h interval or improvement after a 6 h interval of performance was observed, respectively. The CCKB agonist, BC 264, was ineffective after a 2 h time interval, whereas the dose of 0.3 μg/kg significantly enhanced performance after a 6 h inter-trial interval. In contrast, BC 197 (30 μg/kg) produced a significant disruption of performance after a 2 h inter-trial interval but was without effect after a 6 h time interval. The effects of the two CCKB agonists were abolished by pretreatment with a selective CCKB antagonist, L365,260 but not by a selective CCKA antagonist, L364,718. The present results suggest that CCKB receptors display functional heterogeneity and that CCKB agonists like BC 264 could offer a new perspective for the treatment of attentional and/or memory deficits.

Opioids in Pain Control: Basic and Clinical Aspects
http://books.google.co.uk/books?id=...sb0UFw9&sig=YFq-U3jHnJE3I9ot6N89048yjyI&hl=en


Life Sciences
Volume 62, Issue 10, 30 January 1998, Pages 947-952

Abstract

The ability of a pretreatment with the cholecystokininB-receptor (CCKB) antagonist L-365,260 to prevent the development of morphine dependence was studied in normal and neuropathic (unilateral peripheral neuropathy) rats. A 4-day pretreatment regimen with two daily s.c. injections of either saline+saline, saline+morphine (3.0 mg/kg) or L-365,260 (0.2 mg/kg)+morphine was used, and withdrawal was precipitated by an injection of naloxone (1.0 or 2.0 mg/kg i.v.) at 24 h after the last pretreatment injection. After pretreatment with morphine alone, physical dependence developed in both normal and neuropathic rats. However, the incidence of teeth chattering and ptosis was higher in neuropathic rats. Pretreatment with the combination of L-365,260 and morphine prevented the expression of teeth chattering, ptosis, diarrhea, writhing and piloerection, but was devoid of effects on the exploratory activity among both groups of rats. These results suggest that endogenous CCK acting on CCKB-receptors may be involved in the development of morphine dependence both in normal and neuropathic rats.

The selective CCK-B receptor antagonist L-365,260 enhances morphine analgesia and prevents morphine tolerance in the rat.
Author: Dourish, C T : O'Neill, M F : Coughlan, J : Kitchener, S J : Hawley, D : Iversen, S D
Eur-J-Pharmacol. 1990 Jan 25; 176(1): 35-44

The effects of the selective CCK-A antagonist L-365,031 and the selective CCK-B antagonist L-365,260 on morphine analgesia and opiate tolerance and dependence in rats were examined. L-365,031 and L-365,260 had no effect on baseline pain thresholds in the radiant heat tail flick test but enhanced analgesia induced by a submaximal dose of morphine (4 mg/kg). Similarly, L-365,260 did not effect pain thresholds in the paw pressure test but enhanced morphine analgesia in this model. Rats injected twice daily for 6 days with incremental doses of morphine became tolerant to the analgesic effects of the drug. Twice daily injections of either 8 mg/kg L-365,031 or 0.2 mg/kg L-365,260 prevented the development of tolerance to morphine analgesia. In contrast, L-365,260 had no influence on the development of opiate dependence in these animals, as assessed by naloxone-precipitated withdrawal. The results of the present study, when considered together with previous data, indicate that the rank order of potency of non-peptide CCK antagonists for enhancing morphine analgesia is L-365,260 greater than MK-329 greater than L-365,031. This rank order correlates well with the potency of the antagonists in blocking CCK-B receptors in rodents and suggests that CCK/opiate interactions in this species are mediated by CCK-B receptors.

 

[mad_scientist]

The anti-ulcer drug proglumide is a small molecule cholecystokinin antagonist (non-selective but that doesn't matter much) which both enhances analgesia produced by opioids and prevents or even reverses the development of tolerance.

Despite being the only CCK antagonist that I'm aware of thats actually been widely marketed its hardly used any more because more effective anti-ulcer drugs are available, even though there are virtually no other drugs available which enhance the action of opioids in the same way.

Certainly an interesting area, seems odd that the research into these drugs stalled and went nowhere, from the reviews I read the drugs which performed well in animals had poor efficacy in humans, most likely due to limited oral bioavailability, but thats never really been a serious barrier to drug development in the past.

http://en.wikipedia.org/wiki/Proglumide

http://en.wikipedia.org/wiki/Cholecystokinin_antagonist

 

[Ham-milton]

Yeah, but it's also a delta-antagonist

 

[The Monkey Mantra]

The problem with the proglumide-for-opiate-tolerance issue is that, as far as I've read, after two weeks you get tolerant to this effect. Sorry guys, but the brain will ALWAYS find its way back to homeostasis!

 

[redeemer]

Sorry guys, but the brain will ALWAYS find its way back to homeostasis!

Agreed. A temporary change in homeostasis can be achieved by constant intake of a drug. The only long term solution, as I see it, is permanently changing what actually constitutes homeostasis. And doing so is - at the moment - in my opinion only possible via non-drug techniques (ie. various forms of therapy).

 

[vecktor]

complete rubbish.

how does the brain 'know' where the original balance was?

 

[morphiquet]

agree to vecktor.
besides that i have never read any clear definition of what "homeostasis" means in the case of a neuron or a network thereof,
repeated application of any neuroactive drug will always cause permanently lasting changes in behavioral patterns and subjective feelings (and thus change "homeostasis").

 

[redeemer]

complete rubbish.

What is complete rubbish? Do you know of an anti-anxiety medication that causes permanent relief? Increasing doses are required and effects diminish. And when ingestion of the drug is ceased, symptoms return with a stronger intensity than when the treatment was started.
If a person has anxiety there is obviously some or several mechanisms in the brain causing this anxiety to appear. When a drug wears off the exact same mechanisms are still present and will cause the anxiety to appear again.

how does the brain 'know' where the original balance was?

How it "knows" I can't tell you, but obviously it "knows". I've never heard of anyone not coming down from a drug. But I don't think it's a matter of "knowing". Just as when throwing a ball at a certain speed and angle, it will land exactly the same place if the throws are identical. One could ask how the ball "knows" to land at that specific place, but I think it's just a matter of it following the rules that are present.

An exception to this would be psychedelic drugs. But I think they act more as a catalyst for an experience that causes the relief.

 

[MeDieViL]

Could CCKB2 antagonists have potential for more then opiate tolerance? Lets see what we got:

Self-administration of intravenous amphetamine: effect of nucleus accumbens CCKB receptor activation on fixed-ratio responding.
Bush DE, DeSousa NJ, Vaccarino FJ.

Department of Psychology, University of Toronto, Ontario, Canada.
RATIONALE: The mesolimbic dopamine (DA) system is implicated in psychostimulant drug self-administration. The neuropeptide cholecystokinin (CCK) is co-localised with DA and inhibits nucleus accumbens (NAcc) DAergic neurotransmission via CCKB receptors. OBJECTIVES: The present experiment was designed to examine the effects of intra-NAcc CCKB receptor stimulation on fixed-ratio (FR) amphetamine self-administration. METHODS: Wistar rats with intravenous catheters and NAcc cannulae were trained to self-administer amphetamine under a FR3 schedule of reinforcement. Animals performing stable self-administration were microinjected with pentagastrin and assessed during 3-h sessions. RESULTS: Intra-NAcc pentagastrin dose dependently increased amphetamine intake. CONCLUSIONS: These results are consistent with the notion that NAcc CCKB receptor activation attenuates amphetamine reward.

Interaction of CCKB receptors with amphetamine in responding for conditioned rewards.
Josselyn SA, Vaccarino FJ.

Department of Psychology, University of Toronto, Ontario, Canada.
Cholecystokinin (CCK) has been localized in the nucleus accumbens (NAC) where it may interact with dopamine neurotransmission. NAC dopamine is involved in the control over behavior produced by conditioned rewards. The present experiment tested the whether blockade of endogenous CCKB receptors with L-365,260 (0.1 mg/kg, IP) potentiates bar pressing for stimuli previously associated with food reward. Intra-accumbens amphetamine (20 micrograms) facilitated bar pressing for conditioned rewards. Systemic administration of L-365,260 potentiated this amphetamine response but produced no effect on responding when administered alone. These findings suggest that endogenous CCKB mechanisms may normally inhibit DA function in reward-related behaviors.

Evidence for the contribution of CCKB receptor mechanisms to individual differences in amphetamine-induced locomotion.
Higgins GA, Sills TL, Tomkins DM, Sellers EM, Vaccarino FJ.

Addiction Research Foundation, University of Toronto, Ontario, Canada.
Recent evidence shows that rats exhibit individual differences in their locomotor response to amphetamine (AMP). Moreover, evidence has accumulated showing that high-AMP responders exhibit more mesolimbic dopaminergic (DAergic) activation in response to AMP treatment than low-AMP responders. Cholecystokinin (CCK) is a peptide that is colocalised with mesolimbic DA and exerts complex modulatory actions on DA function. Two CCK receptor subtypes have been identified and selective antagonists have been developed. To examine the possible contribution of endogenous CCK mechanisms to individual differences in responsivity to AMP treatment, male Wistar rats were divided into low- and high-AMP responders based on a median split of their locomotor response to AMP and the effects of the selective CCK antagonists L365-260 (CCKB; 0.01, 0.1, 0.5 mg/kg; n = 16) and devazepide (CCKA; 0.001, 0.01, 0.1 mg/kg; n = 23) were determined. Results showed that L365-260 (0.1 mg/kg) potentiated AMP-induced hyperactivity in low-AMP responders but did not affect AMP-induced hyperactivity in high-AMP responders. Devazepide was without effect in both groups of animals. This pattern of results suggests that CCKB, but not CCKA, receptor mechanisms contribute to interindividual variation in responsivity to AMP.

Differences in behavioural effects of amphetamine and dopamine-related gene expression in wild-type and homozygous CCK2 receptor deficient mice.
Rünkorg K, Värv S, Matsui T, Kõks S, Vasar E.

Department of Physiology, University of Tartu, Ravila 19, Tartu 50411, Estonia. [email protected]
Neuropeptide cholecystokinin (CCK) interacts with dopamine in the regulation of motor activity and motivations. Therefore, in CCK(2) receptor deficient mice the behavioural effects of repeated amphetamine administration and changes in dopamine-related gene expression were studied. Four-day amphetamine (1 mg/kg) treatment induced a significantly stronger motor sensitization in homozygous mice compared to their wild-type littermates. However, in the conditioned place preference test the action of amphetamine was more pronounced in wild-type animals. As opposed to wild-type mice, amphetamine (1-3 mg/kg) did not cause a significant conditioned place preference in homozygous mice. The expression of Tyhy gene was elevated in the mesolimbic structures and Drd2 gene was down-regulated in the mesencephalon of saline-treated homozygous mice in comparison with respective wild-type group. Four-day treatment with amphetamine induced a significant increase in the expression of Tyhy in the mesencephalon, striatum and mesolimbic structures of wild-type mice, whereas in homozygous mice a similar change was evident only in the mesencephalon. Also, the expression of Drd1 gene in the striatum and Drd2 gene in the mesolimbic structures of wild-type mice were up-regulated under the influence of amphetamine. In conclusion, the present study established differences in the behavioural effects of amphetamine in wild-type and homozygous mice. The increased tone of dopaminergic projections from the mesencephalon to mesolimbic structures is probably related to increased amphetamine-induced motor sensitization in homozygous mice. The lack of development of up-regulation of Drd1 and Drd2 genes after repeated treatment with amphetamine probably explains the reduced place conditioning in CCK(2) receptor deficient mice.

Effect of CCK1 and CCK2 receptor blockade on amphetamine-stimulated exploratory behavior and sensitization to amphetamine.
Alttoa A, Harro J.

Department of Psychology, Center of Behavioral and Health Sciences, Tartu University, Tiigi 78, 50410 Tartu, Estonia.
Interactions between dopaminergic neurotransmission and cholecystokinin (CCK) in the CNS may be important in the pathogenesis of psychotic disorders and substance abuse. In this study, the effect of coadministration of the selective CCK receptor antagonists devazepide and L-365,260 (for selectively blocking CCK1 and CCK2 receptors, respectively), on the effect of amphetamine on the rat exploratory behavior, and on sensitization of locomotor response to amphetamine, were studied. Amphetamine (0.5 mg/kg) increased exploratory activity in the exploration box for 5 consecutive testing days, while devazepide (10 microg/kg) blocked and L-365,260 (10 microg/kg) enhanced amphetamine-induced stimulation of activity. Devazepide coadministration prevented the development of sensitization to amphetamine, while coadministration of L-365,260 with amphetamine potentiated the locomotor effect of a challenge dose of amphetamine. These results suggest that endogenous CCK, released during exploratory activity, shapes behavioral responses to amphetamine by acting on both receptor subtypes, and modulates the development of sensitization to amphetamine.

CCK2 receptor-deficient mice have increased sensitivity of dopamine D2 receptors.
Kõks S, Abramov U, Veraksits A, Bourin M, Matsui T, Vasar E.

Department of Physiology, Biomedicum, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia. [email protected]
The present study supports a role of CCK(2) receptors in the regulation of dopamine neurones. In pharmacological studies conducted on male CCK(2) receptor-deficient mice the changes in the activity of dopamine system were established. A low dose of dopamine agonist apomorphine (0.1 mg/kg), stimulating the pre-synaptic dopamine receptors, induced significantly stronger suppression of locomotor activity in mutant mice (-/-) compared to their wild-type littermates (+/+). The administration of amphetamine (3-6 mg/kg), a drug increasing dopamine release, caused a dose-dependent stimulation of locomotor activity in wild-type mice. In mice lacking CCK(2) receptors, a lower dose of amphetamine (3 mg/kg) tended to suppress the motor activity, whereas the higher dose (6 mg/kg) induced the significantly stronger motor stimulation in mutant mice. Moreover, in the CCK(2) receptor-deficient mice the affinity of dopamine D(2) receptors, but not 5-HT(2) receptors, was increased. Altogether, the targeted genetic suppression of CCK(2) receptors increased the sensitivity of pre- and post-synaptic dopamine D(2) receptors.

Targeted mutation of CCK2 receptor gene modifies the behavioural effects of diazepam in female mice.
Raud S, Rünkorg K, Veraksits A, Reimets A, Nelovkov A, Abramov U, Matsui T, Bourin M, Volke V, Kõks S, Vasar E.

Department of Physiology, Biomedicum, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia.
RATIONALE: Evidence suggests that GABA and CCK have opposite roles in the regulation of anxiety. OBJECTIVE: The aim of the present work was to study diazepam-induced anxiolytic-like action and impairment of motor co-ordination, and the parameters of benzodiazepine receptors in mice lacking CCK2 receptors. METHODS: The action of diazepam (0.5-3 mg/kg i.p.) was studied in the elevated plus-maze model of anxiety and rotarod test using mice lacking CCK2 receptors. The parameters of benzodiazepine receptors were analysed using [3H]-flunitrazepam binding. RESULTS: In the plus-maze test, the exploratory activity of the homozygous (-/-) mice was significantly higher compared to their wild-type (+/+) littermates. However, the wild-type (+/+) mice displayed higher sensitivity to the anxiolytic-like action of diazepam. Even the lowest dose of diazepam (0.5 mg/kg) induced a significant increase of open arm entries in the wild-type (+/+) mice. A similar effect in the homozygous (-/-) mice was established after the administration of diazepam 1 mg/kg. The highest dose of diazepam (3 mg/kg) caused a prominent anxiolytic-like effect in the wild-type (+/+) mice, whereas in the homozygous (-/-) animals suppression of locomotor activity was evident. The performance of the homozygous (-/-) mice in the rotarod test did not differ from that of the wild-type (+/+) littermates. However, a difference between the wild-type (+/+) and homozygous (-/-) animals became evident after treatment with diazepam. Diazepam (0.5 and 3 mg/kg) induced significantly stronger impairment of motor co-ordination in the homozygous (-/-) mice compared to their wild-type (+/+) littermates. The density of benzodiazepine binding sites was increased in the cerebellum, but not in the cerebral cortex and hippocampus, of the homozygous (-/-) mice. CONCLUSIONS: Female mice lacking CCK2 receptors are less anxious than their wild-type (+/+) littermates. The reduced anxiety in homozygous (-/-) mice probably explains why the administration of a higher dose of diazepam is necessary to induce an anxiolytic-like action in these animals. The highest dose of diazepam (3 mg/kg) induced significantly stronger suppression of locomotor activity and impairment of motor co-ordination in the homozygous (-/-) mice compared to the wild-type (+/+) littermates. The increase in the action of diazepam is probably related to the elevated density of benzodiazepine receptors in the cerebellum of homozygous (-/-) mice. The present study seems to be in favour of increased tone of the GABAergic system in mice without CCK2 receptors.

How exactly does the reversal of opiate tolerance work with proglumide in those mice? Does proglumide upregulate the opiate receptors so that after administration of proglumide those receptors still have regained there sensitivity or does proglumide only work when co administered with morphine?

If proglumide actually upregulates those receptors, ive been thinking that it may also upregulate dopamine and benzodiazepine receptors since those are more sensitive in knockout mice.