Cholecystokinin peptides in cerebrospinal fluid: a study in healthy male subjects lumbar-punctured without preceding strict bed-rest

Summary. In a recent study we analysed the concentrations of two forms of cholecystokinin (CCK), CCK-8S (sulphated) and CCK-4 in cerebrospinal fluid (CSF) obtained from 14 healthy male volunteers lumbar-punctured after a minimum of eight hours of strict bed-rest. We have now lumbar-punctured another group of 14 healthy males, using the same procedure except for the requirement of strict bed-rest prior to puncture. In contrast to our previous study, the concentration of CCK-4 (but not CCK-8S) was significantly higher in the second CSF fraction (7–12 ml) than in the first one (0–6 ml). On using the concentration ratio between the second and first fraction, CCK-8S (but not CCK-4) correlated positively with the atmospheric pressure, which is in contrast to our previous study in which a significant negative correlation was found. When the lumbar CSF concentrations were expressed as the concentration per minute of tapping-time (an estimate of the mass flow), atmospheric pressure, age and the neuraxis distance in the lying position made significant contributions to the variance in CCK-8S. A significant positive correlation with atmospheric pressure was found for CCK-4. In conclusion, the results indicate that the question of strict bed-rest or not prior to lumbar puncture may have to be considered when interpreting data on lumbar CSF concentrations of CCK. A controlled study is warranted. Received December 22, 1997; accepted August 4, 1998     

CSF cholecystokinin, γ-aminobutyric acid and neuropeptide Y in pathological gamblers and healthy controls

Summary The sulphated cholecystokinin (CCK) octapeptide (CCK-8S), the CCK tetrapeptide (CCK-4), neuropeptide Y (NPY) and γ-aminobutyric acid (GABA) were determined in cerebrospinal fluid (CSF) obtained from 11 pathological male gamblers and 11 healthy male controls. Compared with healthy controls, pathological male gamblers displayed higher concentrations of CCK-8S, CCK-4 and GABA (but not NPY). A gradient with decreasing concentrations from the first to the third 6-ml CSF fraction was found for CCK-8S, CCK-4 and NPY, but only in pathological gamblers. Disrupted gradients were found for GABA and for NPY in healthy controls. Given that CCK is a modulator of dopamine in the reward process, the increase in CCK-8S and CCK-4 is not unexpected. The high level of GABA in pathological gamblers is in conformity with a compensatory inhibitory action on noradrenergic neurons. The CSF gradient of CCK-8S and CCK-4 in pathological male gamblers (but not healthy controls) might indicate a difference in diurnal variation. The results obtained are in line with an altered CCK and GABA function in pathological gambling. An erratum to this article is available at .     

The regional and subcellular development of cholecystokinin immunoreactivity in vertebrate brain

We have previously demonstrated that the development of CCK in rat brain occurs during the first postnatal month. In order to determine whether the appearance of CCK is associated with specific aspects of brain histogenesis, we examined the development of brain CCK immunoreactivity in both precocial and altricial mammals and birds. The two precocial species (guinea pig and chicken) were found to achieve adult CCK concentrations prenatally, while the altricial species (zebra finch and rat) manifested adult brain CCK concentrations only after several weeks of postnatal development. In adulthood, both mammals showed relatively high forebrain CCK concentrations, while the two species of birds manifested much lower forebrain levels. Brainstem levels of CCK were similar in all species studied. In each species, the development of CCK followed a common time course across all major brain areas, although adult brainstem levels of CCK were generally attained shortly before adult forebrain levels. Correlation of our comparative ontogenetic data with known patterns of brain histogenesis indicated that CCK development follows regional neuroblastic proliferation, migration and differentiation, and occurs during or soon after local synaptogenesis. In the rapidly developing precocial chicken brain, CCK production precedes the postnatal gliogenic and myelinogenic increases in brain weight, suggesting that neurogenic production of CCK occurs independently of these non-neuronal maturation events. Subcellular fractionation of developing chicken brain revealed that a substantial fraction of brain CCK is localized in synaptosomes relatively early in embryogenesis; this synaptosomal localization becomes even more pronounced with further brain maturation. This early appearance of CCK in synaptic terminals indicates a correspondingly precocial maturation for the intraneuronal mechanisms subserving peptide cleavage, axonal transport and vesicular insertion, and suggests that CCK may be available for neurotransmission quite early in development. In an analysis of the molecular forms of CCK, gel filtration disclosed no differences between species or different brain areas in the form of CCK present. CCK-8 always predominated in brain, with smaller void volume (pro-CCK) peaks, and negligible amounts of CCK-33. Finally, duodenal CCK (largely CCK-33) appeared much earlier than brain CCK in all species examined, suggesting that the gut and brain CCK systems develop independently of one another.     

The localization of cholecystokinin immunoreactivity in the rat ovary and uterine tube

The presence of cholecystokinin (CCK) immunoreactive nerve fibres in the rat ovary and uterine tubes was detected using the peroxidase antiperoxidase (PAP) technique. The antibody used was anti CCK 4562 which reacts with CCK-4, CCK-8, CCK-12 and CCK-33 (Larsson and Rehfeld, 1977). CCK-immunoreactive nerve fibres were found between the interstitial cells of the ovary, along blood vessels, and close to smooth muscle fibres in the ovary and tubal wall. A possible role of CCK-nerves in modulation of the sensitivity of the ovarian components to other humoral and nervous stimuli is discussed. The possible control of CCK over smooth muscle fibres in the ovary and the uterine tube and its role in ovulation is a matter of further studies.     

Is cholecystokinin a biological support in panic attacks?]

Cholecystokinin (CCK) is a peptide found high density in the cerebral cortex, the amygdala and the hippocampus of the mammalian brain. Molecular forms of varying amino acid lengths of CCK have been isolated. The sulphated octapeptide (CCK-8S) is the most abundant form and shorter molecular forms are also present in the brain. CCK-8S has been shown to coexist with neurotensin and dopamine in neurons projecting from the ventral tegmental area to the nucleus accumbens, and to a lesser extent in neurons of the substantia nigra projecting to periventricular regions of the caudate. Evidence suggests that CCK acts as a neurotransmitter in the NCS it is synthesized and stored in nerve terminals and cell bodies; it is released by depolarization; it has specific binding sites; it can affect the firing rate of CNS neurons; and its effects can be interfered with by analogues. Studies have found microiontophoretic application of CCK-8S and CCK-4 on cortical and hippocampal neurons to elicit a strong excitatory action. CCK receptors are widely distributed throughout the central nervous system with high densities in the striatum and nucleus accumbens. Considerable effort has been devoted to characterizing the specificity of brain CCK receptors. So far, two types of CCK receptors have been described: CCK-A receptors which have a higher affinity for sulphated CCK-8 than for de-sulphated CCK-8 (CCK-8US), CCK 4 or gastrin, and CCK-B receptors have a high affinity for all of these compounds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement and characterization of neuronal cholecystokinin using a novel radioreceptor assay

This study describes a novel radioreceptor assay (RRA) for cholecystokinin (CCK) which is the first to measure and characterize brain CCK using a technique not dependent on the generation of peptide antibodies. The CCK RRA utilizes the mouse cerebral cortex CCK receptor as the binding source and [125I]BH-CCK-8 as the radiolabelled probe. [125I]BH-CCK-8 bound to the central CCK receptor with a Kd of 1.82 nM and a Bmax of 1.21 pmol/g tissue. Unlabelled CCK-8 displaced the specific binding of [125I]BH-CCK-8 with an inhibition constant of 3.84 nM. CCK was extracted (90% methanol) from discrete brain regions (mouse) and quantified using the CCK RRA. The amygdala contained the highest concentration of CCK (394 +/- 21 pmol/g tissue), followed by the olfactory bulbs (306 +/- 19 pmol/g tissue) and cerebral cortex (298 +/- 21 pmol/g tissue). Moderate levels of CCK were found in the hippocampus (212 +/- 18 pmol/g tissue), striatum (146 +/- 15 pmol/g tissue) and hypothalamus (129 +/- 9 pmol/g tissue). Low levels of CCK were recorded in the pons (45 +/- 5 pmol/g tissue), medulla (41 +/- 3 pmol/g tissue) and spinal cord (29 +/- 3 pmol/g tissue), whilst no CCK was detected in the cerebellum. The molecular forms of CCK in amygdala, cerebral cortex and hypothalamus were characterized using RRA in conjunction with HPLC. CCK-8 was identified as the major molecular form (88%, 94% and 91% of total CCK activity in amygdala, cortex and hypothalamus, respectively) with a smaller component attributable to CCK-4 (8%, 5% and 6% of the total CCK activity).     

Investigation of cholecystokinin system genes in panic disorder.

There is evidence for the role of the cholecystokinin (CCK) neurotransmitter system in the neurobiology of panic disorder (PD). The CCK receptor agonist, CCK-tetrapeptide (CCK-4) fulfills criteria for a panicogenic agent and there is evidence that PD might be associated with an abnormal function of the CCK system. For example, PD patients show an enhanced sensitivity to CCK-4, and exhibit lower CSF and lymphocyte CCK concentration as compared to healthy controls (reviewed by Bradwejn et al.). Also, untreated PD patients display an increased CCK-4-induced intracellular Ca2+ mobilization in T cells relative to treated PD, depression and schizophrenia. The CCK receptors have been classified into two subtypes: CCK-A and CCK-B. We report here a study of polymorphisms in the CCK pre-pro hormone gene (CCK), CCK-AR, and CCK-BR in DSM-IV panic patients (n = 99) vs controls matched for gender and ethnicity. The CCK polymorphism revealed no association with PD. We identified a new polymorphism for the CCK-A receptor gene, and tested it in our sample, with negative results. A single nucleotide polymorphism has been found in the coding region of the CCK-B receptor gene (CCK-BR) and D Collier (personal communication) identified a highly polymorphic dinucleotide (CT)n microsatellite in the 5' regulatory region. For the CCK-B receptor gene polymorphism, PD patients showed a significant association. Our genetic dissection of the CCK system thus far suggests that the CCK-B receptor gene variation may contribute to the neurobiology of panic disorder.     

Cholecystokinin and an evoked response in the dentate gyrus

Cholecystokinin (CCK) as the sulfated (CCK-8S) and unsulfated (CCK-8U) octapeptide sequences, and CR 1409 were administered intraventricularly while the action potential (EAP) in the granular cell layer of the hippocampal dentate gyrus evoked by perforant path stimulation was recorded. No consistent effect of the test substances on the amplitude of the EAP was found at doses corresponding to those previously reported to cause an increase in the EAP when administered systemically. Similarly, no effect of CCK on the EAP could be found when the peptide was administered iontophoretically in the granular cell layer. In contrast, iontophoretically applied CCK-8S, CCK-8U and CR 1409 slightly but consistently reduced the slope of the evoked response recorded in the dentate gyrus molecular layer. These results are interpreted as indicating that the CCK receptor on granular cell dendrites is likely to be the central type that is activated by both CCK-8S and CCK-8U, but that any effects of systemically administered CCK on the EAP are probably mediated in the periphery.     

Autoradiographic localization of cholecystokinin receptors in rodent brain

Cholecystokinin (CCK) receptor binding sites have been localized by autoradiography in the guinea pig and rat central nervous system. [125I]CCK-triacontatriapeptide labeled the sites in brain slices with an observed association constant equal to 0.041 min-1 and a dissociation constant equal to 0.008 min-1. CCK-triacontatriapeptide (CCK-33) and the C-terminal octapeptide of CCK-33 (CCK-8) potently inhibited [125I]CCK-33 binding with Ki's of 2 nM, whereas desulfated CCK-8 (CCK8-ds) and the C-terminal tetrapeptide of CCK-33 (CCK-4) were much weaker. Receptors were concentrated in the olfactory bulb, in the superficial laminae of the primary olfactory cortex, in the deep laminae of the cerebral cortex, and in the pretectal area. Substantial numbers of sites were also found in the basal ganglia, in the amygdala, and in the hippocampal formation. [125I]CCK-33 binding sites appear to be located on fibers of the optic tract and probably on olfactory tract fibers as well. These results are discussed in terms of physiological functions associated with CCK, presynaptic receptors, and axonal flow of CCK receptors.     

Expression, but failing maturation of procholecystokinin in cerebellum.

The cerebellum is the only region of the central nervous system which has been found to be devoid of cholecystokinin (CCK). The assays used, however, have been directed against the alpha-amidated C-terminus of fully processed CCK peptides. Using Northern blot analysis and a library of radioimmunoassays specific for different sequences of proCCK in combination with chromatography and enzyme cleavage, we have now examined the expression and processing of proCCK in fetal, neonatal and adult cerebellar tissue from man, pig and rat. In rat cerebellum CCK mRNA was present already in the fetal state. Two weeks after birth the concentrations declined. Also proCCK was found in significant concentrations in the fetal human and rat cerebellum (approximately 20 pmol/g); but already before birth the expression began to decrease towards low concentrations in adults. The adult porcine cerebellum contained 3.2 pmol proCCK and glycine-extended processing intermediates per gram (range less than 0.1-10.4 pmol/g), and 0.8 pmol carboxyamidated CCK per gram (range 0.1-4.1 pmol/g) varying in size from CCK-58 to CCK-5. For comparison, the adult porcine cerebral cortex contained 757 pmol carboxyamidated CCK/g, 20 pmol glycine-extended CCK/g and no proCCK. We conclude that cerebellum expresses proCCK with the highest level of expression in fetal life. In comparison with other regions of the brain, the maturation to transmitter-active, carboxyamidated CCK peptides is, however, attenuated in both fetal and adult cerebellar tissue.     

Transport of cholecystokinin (CCK) binding sites in subdiaphragmatic vagal branches

In order to evaluate vagal cholecystokinin (CCK) binding sites as potential target sites for the satiety actions of CCK, their presence, axonal flow and pharmacological specificity in subdiaphragmatic vagal branches were examined by autoradiography utilizing 125I-Bolton Hunter CCK-33. Specific CCK binding and axonal transport were found in vagal trunks and all abdominal vagal branches. Binding was inhibited by unlabelled CCK-8, but not by desulfated CCK-8. The pharmacological specificity and transport of CCK binding sites to subdiaphragmatic branches indicate a potential role in mediating CCK's satiety effect.     

Pharmacological and mechanistic studies of cholecystokinin-facilitated [3H]dopamine efflux from rat nucleus accumbens

Cholecystokinin (CCK) is co-localized with dopamine (DA) in mesolimbic neurons of the CNS and appears to selectively regulate the output of this system. In an attempt to characterize the nature of CCK interactions with mesolimbic DA-containing nerve terminals, we have investigated CCK regulation of [3H]DA overflow from rat nucleus accumbens slices. CCK-8 produced a saturable and potent (EC50 = 3 nM) facilitation of KCl (35 mM)-evoked [3H]DA efflux from nucleus accumbens, but failed to significantly alter [3H]DA efflux from striatum: The stimulatory action of CCK-8 was unaffected by the muscarinic antagonist atropine, the opiate antagonist naloxone, or the selective ion channel blockers tetrodotoxin and nifedipine. Pharmacological studies revealed that non-sulfated CCK-8 and CCK-4 (up to low micromolar concentrations) did not facilitate [3H]DA efflux from accumbens slices. Furthermore, the effect of CCK-8 was selectively and potently (IC50 = 300 nM) inhibited by the Type A-selective CCK antagonist CR-1409. Taken together, these results indicate that CCK regulates DA efflux from mesolimbic nerve terminals via a direct presynaptic action on receptors which display a pharmacological profile that is similar to Type A CCK receptors in gastrointestinal tissues.     

Cholecystokinin-8 attenuates methamphetamine-induced inflammatory activation of microglial cells through CCK2 receptor

Methamphetamine (METH) exposure reportedly promotes microglial activation and pro-inflammatory cytokines secretion. Sustained inflammation in abusers of psychostimulant drugs further induces neural damage. Cholecystokinin-8 (CCK-8) is a gut-brain peptide which exerts a wide range of biological activities in the gastrointestinal tract and central nervous system. We previously found that pre-treatment with CCK-8 inhibited behavioural and histologic changes typically induced by repeated exposure to METH. Here, we aimed to estimate the effects of CCK-8 on METH-induced neuro-inflammation, which is markedly characterized by microglia activation and increased pro-inflammatory cytokines production in vivo and in vitro. Moreover, we assessed the subtypes of the CCK receptor mediating the regulatory effects of CCK-8, and the changes in the NF-κB signalling pathway. We found that CCK-8 inhibited METH-induced microglial activation and IL-6 and TNF-α generation in vivo and in vitro in a dose-dependent manner. Furthermore, co-treatment of CCK-8 with METH significantly attenuated the activation of the NF-κB signalling pathway by activating the CCK2 receptor subtype in N9 cells. In conclusion, our findings indicated the inhibitory effect of CCK-8 on METH-induced neuro-inflammation in vivo and in vitro, and suggested the underlying mechanism may involve the activation of the CCK2 receptor, which downregulated the NF-κB signalling pathway induced by METH stimulation.     

Pharmacological and molecular characterization of muscular cholecystokinin receptors in the human lower oesophageal sphincter

In vitro cholecystokinin (CCK) contracts the human lower oesophageal sphincter by stimulating muscular receptors. The aim of this study was to characterize the muscular CCK receptor subtypes in the human lower oesophageal sphincter. Twenty-five circular strips from six patients were studied. RNA was extracted, reverse transcribed, and cDNAs were amplified with primers for human CCK-A and B receptors. The potency of the contraction induced by CCK-8, desulphated CCK-8, and gastrin-I, and the effect of the CCK-A (loxiglumide and SR 27897) and the CCK-B (YM022 and L-365 260) specific receptor antagonists were compared. Both CCK-A and CCK-B receptor mRNAs were found in functional lower oesophageal sphincter strips. The potency of the CCK-8 concentration-dependent contraction was two and three orders of magnitude higher than that of desulphated CCK-8 and gastrin-I, respectively. The CCK-8-induced contraction was blocked by the CCK-A receptor antagonists loxiglumide (IC50 11 micromol L-1) and SR 27897 (IC50 74 nmol L-1) but not by CCK-B receptor antagonists (1 micromol L-1).Our data suggest that, although the human lower oesophageal sphincter expresses both CCK-A and CCK-B receptors, the contractile effect of CCK-8 on the circular muscle is mainly due to the activation of CCK-A receptors.     

Differential effects to CCK-4-induced panic by dexamethasone and hydrocortisone

Abstract Objectives. Peripheral administration of the cholecystokinin (CCK) receptor agonist CCK-4 generates panic and activates the hypothalamic-pituitary-adrenal (HPA) axis. Direct effects at the pituitary and CCK-HPA interactions at higher regulatory sites have been suggested. According to preliminary data, ACTH response to CCK receptor agonists may differ from its response to exogenous CRH by its resistance to cortisol feedback inhibition. To further explore this resistance and to better characterize CCK-4 sites of action, the effects of different glucocorticoid pretreatments on CCK-4-induced panic were compared. Methods. Using a double-blind placebo-controlled design we pretreated healthy males with either dexamethasone (peripheral action) or hydrocortisone (central-peripheral action) each followed by a CCK-4 challenge. Blood levels of ACTH and cortisol were analyzed and panic symptoms were assessed. Results. We found a blunted response of ACTH release following CCK-4 injection only after hydrocortisone pretreatment. Dexamethasone however did not affect CCK-4-induced ACTH release relative to baseline. In contrast to dexamethasone, hydrocortisone reduced the severity of CCK-4-induced panic as measured by the Acute Panic Inventory on a trend level. Conclusions. Findings suggest that CCK-4-induced stress hormone release seems susceptible to cortisol-feedback inhibition and argues for a suprapituitary site of CCK action. Effects on panic anxiety were weak but congruent with studies showing that CCK-4-induced HPA axis inhibition is accompanied by a reduction of anxiety after CCK-4.     

Cholecystokinin-induced protection of cultured cortical neurons against glutamate neurotoxicity

The effects of cholecystokinin (CCK) on glutamate-induced neurotoxicity were examined using cultured rat cortical neurons. Brief exposure of glutamate followed by an incubation with normal solution for more than 60 min reduced cell viability by 60–70%, compared with control values. Glutamate-induced neurotoxicity was significantly inhibited by MK-801 and ketamine, which are non-competitive blockers of N-methyl-d-aspartate (NMDA) receptors. Octapeptide CCK-8S and CCK-related decapeptide ceruletide at concentrations of 10⁻⁹−10⁻⁷ M dose-dependently reduced glutamate-induced neurotoxicity. A desulfated analog CCK-8NS, which acts selectively as an antagonist of CCK_B receptors, also reduced glutamate neurotoxicity. The neuroprotective effects of CCK were antagonized by L-365260, a CCK_B receptor antagonist, but not by L-364718, a CCK_A receptor antagonist. These results suggest that CCK protects cortical neurons against NMDA receptor-mediated glutamate neurotoxicity via CCK_B receptors.     

Endogenous opioids modulate the effect of cholecystokinin on insulin release in dogs

Recently we have demonstrated in dogs and man that endogenous opioids participate in the regulation of pancreatic endocrine function following the ingestion of a meal. Since intestinal hormones such as cholecystokinin (CCK) are also released by the presence of nutrients in the gastrointestinal tract and participate in the postprandial stimulation of pancreatic endocrine function, an interaction between CCK and endogenous opioids seems possible. The present study was designed to examine this further. In a group of 8 conscious dogs the octapeptide of CCK was infused intravenously in its sulfated (CCK-8S) or nonsulfated (CCK-8NS) form and in addition the tetrapeptide of CCK (CCK-4) was given at increasing infusion rates of 50, 200 and 500 pmol/kg . h, respectively. The experiments were performed during a background infusion of saline to assess the effect on basal insulin and during a background infusion of glucose (0.2 g/min) to determine the effects on stimulated insulin release. The effect of endogenous opioids was examined by addition of the opiate-receptor antagonist naloxone. The studies demonstrate that in the basal state CCK-8S has no stimulatory effect on insulin secretion unless naloxone is added indicating that endogenous opioids help to prevent insulin secretion in the absence of elevated glucose levels. During i.v. glucose naloxone reduced the stimulatory effect of CCK-8S at 50 and 200 pmol/kg . h and that of CCK-4 at 50 pmol/kg . h. Infusion of CCK-8S and CCK-4 at 500 pmol/kg . h had no effect on glucose-stimulated insulin levels, however, the addition of naloxone elicited a significant stimulatory effect. These data demonstrate stimulatory as well as inhibitory effects of endogenous opioids depending on the dose of CCK-8 and -4. CCK-8NS reduced glucose-stimulated insulin release already at the lowest dose of 50 pmol/kg . h. This was reversed to a stimulatory effect with the addition of naloxone. These data demonstrate that the interaction between CCK-8 and -4 and endogenous opioids on prestimulated insulin secretion is much more dependent on the dose of CCK - low doses induce stimulatory and high doses inhibitory mechanisms via endogenous opioids. In view of previous in vitro and in vivo studies with exogenously infused opiate-active compounds it might be speculated that increasing doses of CCK elicit a parellel increase in the release of endogenous opioids which might be responsible for some but certainly not all of the effects observed recently for the action of naloxone in the post-prandial state.     

Very low levels of cholecystokinin octapeptide activate Na-pump in the cerebral cortex of CCK2 receptor-deficient mice

This study provides the first evidence that CCK-8 (0.01 pM to 0.1 mM) stimulates Na,K-ATPase in the cortical membranes of wild-type and CCK(2) receptor-deficient mice. In each genotype, the maximal stimulation was about 40%. Homozygous mice revealed substantially lower EC50 (4 pM) than heterozygous (37 pM) or wild-type animals (682 pM). In homozygous CCK2 receptor-deficient mice, the expression of CCK1 receptor gene was 5-fold higher than in wild-type animals. CCK1 receptor antagonist devazepide counteracted effect of CCK-8 in all three genotypes, whereas CCK2 receptor antagonist L-365, 260 showed significant antagonism in wild-type and heterozygous mice. The cooperativity of Na,K-ATPase for Na+, but not for K+, was lost in homozygous mice. Altogether, very low concentrations of CCK-8 via CCK1 and CCK2 receptors stimulate Na,K-ATPase in the cerebral cortex. CCK2 receptor-deficiency leads to the altered functionality of Na,K-ATPase that might be compensated by CCK1 receptor mediated influence of CCK (and its agonists) on the enzyme.     

Differential effects to CCK-4-induced panic by dexamethasone and hydrocortisone

Abstract

Objectives. Peripheral administration of the cholecystokinin (CCK) receptor agonist CCK-4 generates panic and activates the hypothalamic–pituitary–adrenal (HPA) axis. Direct effects at the pituitary and CCK-HPA interactions at higher regulatory sites have been suggested. According to preliminary data, ACTH response to CCK receptor agonists may differ from its response to exogenous CRH by its resistance to cortisol feedback inhibition. To further explore this resistance and to better characterize CCK-4 sites of action, the effects of different glucocorticoid pretreatments on CCK-4-induced panic were compared. Methods. Using a double-blind placebo-controlled design we pretreated healthy males with either dexamethasone (peripheral action) or hydrocortisone (central-peripheral action) each followed by a CCK-4 challenge. Blood levels of ACTH and cortisol were analyzed and panic symptoms were assessed. Results. We found a blunted response of ACTH release following CCK-4 injection only after hydrocortisone pretreatment. Dexamethasone however did not affect CCK-4-induced ACTH release relative to baseline. In contrast to dexamethasone, hydrocortisone reduced the severity of CCK-4-induced panic as measured by the Acute Panic Inventory on a trend level. Conclusions. Findings suggest that CCK-4-induced stress hormone release seems susceptible to cortisol-feedback inhibition and argues for a suprapituitary site of CCK action. Effects on panic anxiety were weak but congruent with studies showing that CCK-4-induced HPA axis inhibition is accompanied by a reduction of anxiety after CCK-4.     

Receptor selectivity of cholecystokinin effects on mesoaccumbens dopamine neurons

Extracellular recording techniques were combined with antidromic stimulation to examine the effects of C-terminal cholecystokinin (CCK) fragments and CCK antagonists on the activity of identified mesoaccumbens dopamine (MADA) neurons in chloral hydrate-anesthetized rats. These experiments were designed to determine the receptor selectivity of sulfated CCK octapeptide (CCK-8S) effects on MADA cells. Neither CCK tetrapeptide (CCK-4) nor unsulfated CCK octapeptide (CCK-8U) significantly altered MADA cell basal firing rate or responsiveness to the inhibitory effects of the D2 DA agonist quinpirole. As reported previously for ventral tegmental area DA cells, CCK-8S produced increases or decreases in the firing rate of most MADA cells sampled. CCK-8S also enhanced the sensitivity of MADA neurons to quinpirole-induced inhibition. This increase in sensitivity to quinpirole was blocked by pretreatment with the nonselective CCK receptor antagonist proglumide and the preferential CCK-A receptor antagonist CR 1409 but not by the preferential CCK-B receptor antagonist L-365,260. The inactivity of CCK-4 and CCK-8U in these tests and the results with the antagonists suggest that the effects of CCK-8S on MADA neuronal activity are mediated by CCK-A receptors.