Cholecystokinin in plasma and cerebrospinal fluid--a study in healthy young women

Cholecystokinin (CCK) is widely distributed in the brain and is known to affect behavioral and physiological functions including anxiety and pain. The expression of CCK has been shown to be regulated by estrogen and to vary during the estrous cycle in rat brain. In the present study CCK was determined in plasma from 25 healthy women (age 25.0+/-3.5) during the menstrual cycle, in the late luteal phase and in the follicular phase. In the follicular phase, a lumbar puncture was performed at the same time that a plasma sample was taken in 15 subjects. The participants had fasted and were nicotine-free for at least 8h preceding the sampling. We compared CCK-like immunoreactivity (CCK-LI) in plasma from 25 subjects in the late luteal phase (LLP) and the follicular phase (FP) and found that there was no difference during the menstrual cycle (n=25, R(2)=89.60%, p=n.s.). In the follicular phase no significant difference was found between CCK-LI in plasma and in cerebrospinal fluid (CSF) collected at the same time (n=15, R(2)=55.32%, p=n.s.).

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

The sulphated cholecystokinin (CCK) octapeptide (CCK-8S), the CCK tetrapeptide (CCK-4), neuropeptide Y (NPY) and gamma-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.

The role of spinal cholecystokinin in chronic pain states

It is well established that cholecystokinin (CCK) reduces the antinociceptive effect of opioids. The level of CCK and CCK receptors, as well as CKK release, exhibits considerable plasticity after nerve injury and inflammation, conditions known to be associated with chronic pain. Such altered CCK release coupled in some situation with changes in CCK receptor levels may underlie the clinical phenomenon of varying opioid sensitivity in different clinical pain conditions. In particular, neuropathic pain after injury to the peripheral and central nervous system does not respond well to opioids, which is likely to be caused by increased activity in the endogenous CCK system. CCK receptor antagonists may thus be useful as analgesics in combination with opioids to treat neuropathic pain.

Increased level of cholecystokinin in cerebrospinal fluid is associated with chronic pain-like behavior in spinally injured rats

Cholecystokinin (CCK) is a physiological antagonist of opioid-mediated antinociception and may be involved in some chronic pain states where opioids have reduced effect. We have previously shown in a rat model of central neuropathic pain after spinal cord injury that blockade of CCK-B receptors lead to marked pain relief. In the present study, we showed that spinally injured rats exhibiting chronic pain-like behaviors (aversive reaction to innocuous mechanical and cold stimulation) had significantly elevated level of CCK-like immunoreactivity in cerebrospinal fluid compared to normal rats or spinally injured rats which did not exhibit pain-like behaviors. The increased level of circulating CCK in the cerebrospinal fluid may thus contribute to the maintenance of chronic pain in these rats by reducing the endogenous inhibitory tone provided by opioid peptides and may be involved in the phenomenon of opioid insensitivity.

Cholecystokinin and panic disorder--three unsettled questions

The serendipitously discovered panicogenic effect of the cholecystokinin fragment, the C-terminal tetrapeptide amide (CCK-4), has suggested that the widespread network of CCK neurons and corresponding CCK-B receptors in the brain are in some way involved in pathogenesis panic disorders in man. Two decades of research have now established that exogenous CCK-4 in a reproducible, dose-dependent and sensitive manner indeed evokes panic attacks in both healthy subjects and at even lower doses in anxiety patients. But several questions about the molecular mechanisms by which endogenous CCK peptides may precipitate panic attacks remain to be answered. This review focuses on three immediate questions. (1) Does endogenous CCK-4 exist? (2) Is the panicogenic effect mediated only through CCK-B receptors? (3) Are measurements of CCK peptides in cerebrospinal fluid of use in elucidating the pathogenesis and/or diagnosis? This review concludes that the answers to these questions may further the understanding of panic disorder substantially, and hence contribute to improved diagnosis and therapy of the disease.

Intra- and inter-individual correlations between cholecystokinin and corticotropin-releasing hormone concentrations in human cerebrospinal fluid

Despite strong evidence of a physiologic relationship between cholecystokinin (CCK) and corticotropin-releasing hormone (CRH) in the rat central nervous system (CNS), evidence of such a relationship between the two hormones in the human CNS is lacking. A post hoc analysis of serial concentrations of immunoreactive CCK and CRH, obtained every ten minutes from CSF continuously collected over six hours, was performed. A total of 30 subjects were studied: 15 normal volunteers, 10 patients with major depression, and 5 recently-abstinent, alcohol-dependent patients. Overall, we observed an average intra-subject correlation of +.273 (P < 0.001) between CSF CRH and CCK. Inter-subject correlations between mean CSF levels of CRH and CCK were +.948 (P = 0.0001) and +.959 (P = 0.005) in the depressed and abstinent alcoholic patients, respectively. These inter-individual correlations were significantly greater than that seen within the group of normal volunteers (r = +.318, n.s.). The present data suggest that interactions between CCK and CRH are significant in the human CNS, particularly perhaps in depressed and alcoholic patients, and that CSF samples may be used to assess elements of the relationship between these hormones.

How to measure cholecystokinin in tissue, plasma and cerebrospinal fluid

This review examines a major problem for an old hormone. Hormones are defined by the ability to reach their targets via blood. Consequently, knowledge about a hormone requires measurement of its behaviour in blood. So far, however, it has proven exceptionally difficult to measure the classical gut hormone, cholecystokinin (CCK), in circulation. The review therefore describes the premises for reliable plasma CCK measurements as compared to the premises for measurement in tissue extracts and cerebrospinal fluid. The critical plasma premises comprise equimolar quantitation of the bioactive CCK peptides in circulation (CCK-83, -58, -33, -22 and -8) without interference from homologous gastrin peptides. The latter may appear nearly impossible, because the bioactive epitopes of CCK and gastrin are almost identical, and because the plasma concentrations of gastrin are more than tenfold above those of CCK. In comparison, measurement of CCK in tissue is considerably simpler, especially in extracts of the two main production sites, the brain and jejunoileal mucosa. For cerebrospinal fluid, degradation, low levels and shortage of material constitute major problems so that the molecular nature and biological/clinical relevance of CCK measurements in CSF still remain to be settled. The review finally enlists the reports on plasma CCK measurements published so far. A multitude of different immuno- and bioassays have been used with corresponding variation in the results. The theory for different types of assays in combination with general assay experience suggest that accurate CCK measurements require radioimmunoassay technology based on high-affinity antibodies. These antibodies have to be exquisitely specific for the 0-sulfated C-terminal heptapeptide amide of CCK without binding the similar gastrin epitope. Only few of such antibodies have been raised.

Cholecystokinin in CSF from depressed patients: possible relations to severity of depression and suicidal behaviour

Levels of cholecystokinin (CCK) peptides were measured in the CSF from 105 patients suffering from major depressive disorders admitted to a research psychiatric ward for diagnostic evaluation, by a radioimmunoassay method using two different antibodies. Relations between CCK levels and parameters of depression, anxiety, and suicidal behaviour were investigated. Significant inverse correlations were found between CCK levels and certain depression and anxiety parameters. Patients who had made one or more suicide attempts tended to have higher CSF CCK levels than those who had not. No correlations were found between CSF CCK and 5-HIAA or HVA, or with plasma cortisol.

Decreased cholecystokinin levels in cerebrospinal fluid of patients with adult chronic hydrocephalus syndrome

Cholecystokinin (CCK) levels were measured in cerebrospinal fluid (CSF) of patients with adult chronic hydrocephalus syndrome (ACHS) (n = 16) and compared with levels from a control group (n = 11). The CSF concentration of CCK in the ACHS group (0.79 +/- 0.53 fmol/mL) was significantly reduced (p = .002) with respect to the controls (1.55 +/- 0.54 fmol/mL). As CCK-8, the most prevalent from of CCK in the central nervous system, has been demonstrated to play a significant role in several physiological and behavioral actions, the reduced octapeptide values found in ACHS could be involved in the disturbances associated with this disorder. Continuous monitoring of intracranial pressure (ICP) demonstrated different ICP profiles in ACHS. We found that all patients with abnormal ICP records except one showed CCK values under the detection limit. Three of the 4 patients with normal ICP had CCK levels within the normal range. These preliminary studies could evidence that ICP alterations are responsible for part of the loss of brain neuropeptide levels in ACHS.

Effect of sulpiride or paroxetine on cerebrospinal fluid neuropeptide concentrations in patients with chronic tension-type headache

In lumbar cerebrospinal fluid (CSF) obtained from patients with chronic tension-type headache (CTH), the concentrations of beta-endorphin, met-enkephalin, dynorphin, cholecystokinin (CCK), calcitonin gene-related peptide (CGRP), and somatostatin were measured before and after 8 weeks of treatment with sulpiride or paroxetine. We previously reported higher than normal met-enkephalin concentrations in CTH. The present study reveals normal basal concentrations of CCK, CGRP and somatostatin and slightly decreased dynorphin in the same patients. Treatment with sulpiride or paroxetine did not change the concentration of any of the neuropeptides measured. These data suggest central changes in opioid systems but not in other peptide systems (CCK, CGRP, somatostatin) involved in nociceptive processing at the level of the spinal cord dorsal horn/nucleus caudalis of the trigeminal nerve in CTH. Such central changes might be pathophysiologically important or merely secondary to other more important occurrences. The lack of changes in neuropeptide concentrations during drug treatment makes planning of studies involving CSF analysis easier, but also limits the probability of obtaining information on specific neuropeptide systems through CSF analysis.

Neuropeptides and anxiety: focus on cholecystokinin

Cholecystokinin (CCK), a gastrin-like neuropeptide, exists in the central nervous system in several forms. The octapeptide (CCK-8) occurs in predominantly sulfated form (CCK-8S), and the tetrapeptide (CCK-4) occurs in smaller but significant quantities. This review highlights recent developments in preclinical and clinical research into the potential role for CCK in mediating anxiety states. Relevant animal and human studies of administration of CCK agonists are discussed, as well as recent data regarding the concentration of CCK-8S in cerebrospinal fluid from patients with panic disorder, bulimia nervosa, and obsessive compulsive disorder. Finally, the development of agents that specifically antagonize CCK receptors will be described, as will potential therapeutic uses for these new compounds.

Cholecystokinin in human cerebrospinal fluid: concentrations, dynamics, molecular forms and relationship to fasting and feeding in health, depression and alcoholism

Very little is known about the physiologic significance of the gut-brain hormone cholecystokinin (CCK) in the human central nervous system, although the hormone has been hypothesized to be involved in the regulation of both appetite and anxiety. We continuously collected lumbar cerebrospinal fluid (CSF) via indwelling subarachnoid catheters in ten normal volunteers, ten patients with major depression and five abstinent alcoholic humans, while fasting and after eating. Five other healthy subjects were fasted throughout the experiment. We quantified CSF immunoreactive cholecystokinin (IR-CCK) and glucose concentrations at 10-min intervals from 11.00 to 17.00 h. No difference in CSF IR-CCK concentration, half-life or rhythm was observed between normal volunteers and either depressed or alcoholic patients. Fasting CSF IR-CCK concentrations were 1.3 +/- 0.18, 1.3 +/- 0.21 and 1.2 +/- 0.21 fmol/ml (mean +/- S.E.M.) in normal volunteers, depressed patients and alcoholic patients, respectively. After eating, CSF IR-CCK concentrations rose to 1.5 +/- 0.21, 1.5 +/- 0.24 and 1.4 +/- 0.26 fmol/ml, respectively. Normal volunteers who did not eat had similar basal CSF IR-CCK concentrations (1.1 +/- 0.1 fmol/ml) which similarly rose to 1.4 +/- 0.13 fmol/ml during the sampling interval. In contrast, CSF glucose concentrations rose only in the subjects who ate, beginning to rise after about 1 h and remaining elevated for at least 3 h after eating. These data suggest the existence of a diurnal rhythm of IR-CCK release into CSF, as opposed to a response to feeding. The disappearance half-time of CCK in human CSF is less than 13 min.(ABSTRACT TRUNCATED AT 250 WORDS)

CSF cholecystokinin concentrations in patients with panic disorder and in normal comparison subjects

Cholecystokinin concentrations in the CSF of 25 patients with panic disorder and 16 normal comparison subjects were ascertained by radioimmunoassay. The patients with panic disorder had significantly lower CSF concentrations of cholecystokinin, which may reflect increased CNS cholecystokinin receptor sensitivity, reduced numbers of receptors, or a compensatory reduction in cholecystokinin octapeptide secondary to theoretically increased central cholecystokinin tetrapeptide activity.

Concentration of cholecystokinin in cerebrospinal fluid is decreased in psychosis: relationship to symptoms and drug response

1. Cholecystokinin (CCK) is a neuropeptide which is co-localized within some mesolimbic and mesocortical dopamine neurons. 2. CCK resembles an antipsychotic drug in some pharmacological and behavioral tests. 3. Levels of CCK in the cerebrospinal fluid (CSF) are reduced in eleven drug-free schizophrenics in comparison with six controls. 4. Schizophrenic males have lower CSF CCK levels than females. 5. Rapidity of antipsychotic response to haloperidol appeared to be inversely related to drug-free baseline CSF CCK levels.

Neuropeptides and neural cell adhesion molecule (NCAM) in CSF from patients with ALS

In 10 patients with amyotrophic lateral sclerosis (ALS), the CSF content of the neuropeptides vasoactive intestinal polypeptide (VIP) and cholecystokinin (CCK) as well as neural cell adhesion molecule (NCAM) was investigated. Compared with normal controls, no deviations were found in CCK or NCAM, while the values of VIP were significantly lower in ALS patients. This finding may reflect a loss of motor neurons.

Do concentrations of neurotransmitters measured in lumbar cerebrospinal fluid reflect the concentrations at brain level?

CSF concentrations of vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), noradrenaline (NA) and dopamine (DA) were measured in the lateral ventricles and at the lumbar level in patients with normal pressure hydrocephalus (NPH). The concentrations of VIP (n = 15), NA (n = 10) and DA (n = 10) were significantly higher at the lumbar level than at the ventricular level, whereas the concentrations of CCK (n = 9) were similar at the two sites. A significant positive correlation between the concentrations measured at the two levels was found for VIP (rs = 0.65; p less than or equal to 0.01) and DA (rs = 0.94; p less than or equal to 0.001). The results indicate that the concentrations of transmitter substances measured in CSF at the lumbar level not necessarily are indicative for concentrations measured more centrally. The negative correlations between Evans ratio and L-CSF VIP (rs = -0.76; p less than or equal to 0.001), and between resistance to outflow and V-CSF as well as L-CSF CCK (rs = -0.75); p less than or equal to 0.05) might be explained by a reduction in number of cortical neurons or by disturbances in CSF dynamics in patients with NPH.

Blood-CSF barrier to CCK and effect of centrally administered bombesin on release of brain CCK

The purpose of this study, in part, was to determine the ability of cholecystokinin (CCK-33/39 and CCK-8) to penetrate the blood cerebrospinal fluid (CSF) barrier in dogs by measuring these forms of CCK in plasma and in CSF. In addition, the effectiveness of centrally administered bombesin in releasing brain CCK-33/39 and CCK-8 was evaluated. Six groups of five dogs each were studied. Each group received one of the following: (1) intravenous infusion of CCK-33/39 (1.3 micrograms/kg/hr); (2) intravenous infusion of CCK-8 (0.4 micrograms/kg/hr); (3) intrathecal infusion of CCK-33/39 (1.3 micrograms/kg/hr); (4) intrathecal infusion of CCK-8 (0.5 micrograms/kg/hr); (5) intravenous infusion of bombesin (1 micrograms/kg/hr); and (6) intrathecal infusion of bombesin (1 microgram/kg/hr). Plasma concentrations of CCK-33/39 significantly increased during intravenous infusion of CCK-33/39 (from basal of 84 +/- 8 to 142 +/- 2 pg/ml) or bombesin (from basal of 78 +/- 13 to 325 +/- 87 pg/ml); however, CSF perfusate concentrations of CCK-33/39 did not increase. CCK-33/39 levels of the CSF perfusate increased significantly (P less than .05) from 211 +/- 84 to 9,873 +/- 3,368 pg/ml during intrathecal infusion of CCK-33/39, but failed to rise simultaneously in the systemic circulation. Similarly, intravenous infusion of CCK-8 caused a fivefold elevation in plasma CCK-8 levels and no change in CSF perfusate levels of CCK-8; moreover, intrathecal infusion of CCK-8 failed to elevate peripheral CCK-8 levels, despite CSF perfusate CCK-8 levels of 92,300 +/- 18,598 pg/ml. Intrathecal concentrations of neither CCK-33 nor CCK-8 were affected by intravenous or intrathecal administration of bombesin. We conclude that CCK-33/39 and CCK-8 do not penetrate the blood-cerebrospinal fluid barrier in dogs, and centrally administered bombesin is ineffective in causing release of cholecystokinin from brain tissue into the CSF.

Neuronal cholecystokinin and schizophrenia: pathogenic and therapeutic studies

Neuroleptic-free schizophrenic patients received caerulein, a potent analogue of cholecystokinin octapeptide, in a fixed- and rising-dose schedule. In addition, neuroleptic-treated patients received a single dose of the peptide with a 4-week follow-up. No significant change in mental status was observed after any of these administration schedules. Peak plasma levels of caerulein were noted at 20-30 min after IM administration; at this time no changes in cortical evoked potential were demonstrated. Furthermore, levels of cholecystokinin were not found to be reduced, but were in fact elevated in lumbar cerebrospinal fluid of schizophrenic patients. These data argue against the antipsychotic efficacy of systemic caerulein administration and, because evidence of CNS response to CCK is lacking, suggest that other pharmacologic strategies may be necessary to effectively modify central peptide systems with systemically administered drugs.

Cholecystokinin and neurotensin gradients in human CSF

In successive samples of human lumbar CSF, concentrations of two neurally active peptides, cholecystokinin (CCK) and neurotensin (NT), were compared with levels of homovanillic acid (HVA), the major metabolite of dopamine. Although HVA values progressively increased between the first and 20th milliliter samples, no significant change occurred in the concentration of either peptide. Thus, lumbar CSF levels of CCK and NT, unlike levels of HVA, may not closely reflect amounts of these peptides in supraspinal CSF or brain.

Cerebrospinal fluid cholecystokinin, bombesin and somatostatin in schizophrenia and normals

Cerebrospinal fluid from 31 normals and two groups of phenomenologically similar schizophrenics (n = 72) were collected by identical methods. Radioimmunoassay of CSF was carried out for somatostatin, bombesin, and cholecystokinin. One group of schizophrenics had increased baseline somatostatin and cholecystokinin, and decreased bombesin. No CSF gradient effect was found for the peptides nor were their levels affected by probenecid or pimozide treatment. An inverse correlation was found between bombesin and psychosis rating. Intercorrelation between the peptides and HVA, 5-HIAA, and MHPG were not significant.

Neuropeptides in the cerebrospinal fluid (CSF) in psychiatric disorders

Concentrations of vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK) and gastrin in the cerebrospinal fluid (CSF) was studied in patients with endogenous depression, non-endogenous depression, mania, schizophrenia and a control group. All patients were classified according to various diagnostic systems. In the group of non-endogenously depressed patients CSF-VIP levels (median 16 pmol/l) were found significantly lowered compared to controls (median = 32 pmol/l) and endogenous depression (26 pmol/l). Going through the non-endogenous group it appeared that the low CSF-VIP was due to a group of patients with a former diagnosis of endogenous depression or a present diagnosis of possible endogenous depression. Moreover, this group was clinically characterized by 'dysphoric/hysterical features', 'reversed diurnal variation' (i.e. worst in the evening), and 'lack of clearly circumscribed episode'. In many aspects this group seems similar to the atypical depressions described as monoamineoxidase responders. Concerning CSF-CCK and CSF-gastrin no significant differences between the examined groups were demonstrated.

Vasoactive intestinal polypeptide decreased in cerebrospinal fluid (CSF) in atypical depression. Vasoactive intestinal polypeptide, cholecystokinin and gastrin in CSF in psychiatric disorders

Vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK) and gastrin in the cerebrospinal fluid (CSF) were studied in patients with endogenous depression, non-endogenous depression, mania, schizophrenia and a control group. All patients were classified according to ICD-9 and the group of depressions was further classified according to the Newcastle Rating Scales for depression (Carney et al. 1965) (N-I). In the group of non-endogenously depressed patients, CSF-VIP levels (median 16 pmol/l) were found to be significantly lower than those of controls (median = 32 pmol/l) and endogenous depressives (36 pmol/l). In the non-endogenous group, it appeared that the low CSF-VIP was due to a group of patients who, during a past or present depressive episode, had been diagnosed as suffering from endogenous depression. Moreover, this group was clinically characterized by 'dysphoric/hysterical features', 'reversed diurnal variation' (i.e. worse in the evening), and 'lack of clearly circumscribed episodes'. In many aspects this group seems similar to the atypical depressives described as monoamine oxidase inhibitor responders. Concerning CSF-CCK and CSF-gastrin, no significant differences between the examined groups were demonstrated.

Reduced cholecystokinin immunoreactivity in the cerebrospinal fluid of patients with psychiatric disorders

The close relationship of cholecystokinin peptides with some of the dopamine pathways and the limbic system suggests a putative role for these peptides in the pathophysiology of neuropsychiatric disorders such as Parkinson's disease, manic-depression and schizophrenia. By use of radioimmunoassay, we report a significant decrease in cholecystokinin-immunoreactivity in the cerebrospinal fluid of patients with bipolar manic-depression and untreated schizophrenia in comparison to control subjects.

Rapid appearance of intraventricularly administered neuropeptides in the peripheral circulation

125I-Labeled cholecystokinin octapeptide ([125I]CCK-OP) diffuses rapidly by a non-carrier-mediated mechanism into the peripheral blood following injection into the lateral ventricle of a rabbit. In contrast, no [125I]CCK-OP was observed in the CSF following intravenous injection. This unidirectional free transport mechanism from CSF to blood may apply to other neuropeptides as well.

Altered neuropeptide concentrations in cerebrospinal fluid of psychiatric patients

Immunoreactive somatostatin, bombesin, and cholecystokinin were measured in cerebrospinal fluid of normal subjects and patients with anorexia nervosa, depression, mania, and schizophrenia. Somatostatin-like immunoreactivity was decreased in anorexic and depressed patients. Bombesin-like immunoreactivity tended to be decreased in schizophrenics. Cholecystokinin-like immunoreactivity did not differ between groups. These data suggest a possible function for neuropeptides in regulation of human behavior.

Cholecystokinin antibody injected in cerebral ventricles stimulates feeding in sheep

The role of brain cholecystokinin peptides in satiety was further assessed by using antibody to cholecystokinin to reduce cholecystokinin activity in the cerebrospinal fluid of sheep. Food intakes were increased approximately 100 percent during the 2-hour continuous injection of antibody into the cerebrospinal fluid. This supports the hypothesis that, during feeding, cholecystokinin is released into the cerebrospinal fluid, which transports it to the receptors that elicit satiety.

CCK-octapeptide injected in CSF decreases meal size and daily food intake in sheep

Cholecystokinin octapeptide (CCK-OP) is a potent and specific suppressor of feeding when administered as a continuous lateral cerebral ventricular injection in fasted sheep, and we have proposed that endogenous CCK-OP in the brain is released during meals and acts to terminate feeding. In previous studies, however, only relatively short-term effects of CCK-OP on feeding were examined. In the first experiment of the present series sheep were adapted to a 6-hr feeding period per day. CCK-OP injected continuously for 6 hr into the lateral ventricles reduced feeding during the entire feeding period (809 +/- 72 g, sham; 695 +/- 71 g, carrier; 505 +/- 69 g, CCK-OP; p less than 0.05). In addition mean feed intake for the two days (injection + first post injection day) was significantly reduced by CCK-OP; thus with CCK-OP, sheep did not compensate by the day after injection for the decreased feed intake on injection day. In a second experiment CCK-OP was injected into the lateral ventricles only during four consecutive 15 min meals 2 hours apart. With a dose of 0.159 pmoles/min CCK-OP, size of the second meal was reduced, but with 0.638 pmoles/min CCK-OP feeding during each of the first two meals was reduced and cumulative intake for the four meals was decreased. These results indicate that CCK-OP administered centrally can have long-term effects on feeding, and under appropriate conditions, could result in negative energy balance.

Gastrin and cholecystokinin in human cerebrospinal fluid. Immunochemical determination of concentrations and molecular heterogeneity

To determine whether gastrin and cholecystokinin (CCK), recently found in the central nervous sytem, were present in cerebrospinal fluid (CSF), we studied human specimens by sensitive and specific radioimmunoassays for the two related polypeptide hormones. The concentration of gastrin in cerebrospinal fluid from 10 neurologically normal persons ranged from 1.5 to 8.0 pM (mean 3.4 pM), whereas the concentration of CCK ranged from 4 to 55 pM (mean 14 pM). The molecular heterogeneity of gastrin and CCK in CSF was determined by gel chromatography of concentrated fluid monitored by 3 gastrin radioimmunoassays specific for different sequences of gastrin17 and 3 CCK radioimmunoassays specific for different sequences of CCK33. Chromatography revealed that gastrin was present in molecular forms corresponding to gastrin34 ('big gastrin') and gastrin17. CCK was present in molecular forms corresponding to the COOH-terminal octapeptide amide of CCK33 and a fragment corresponding to sequence 25-29 of CCK33. Also, a peptide corresponding to COOH-terminal tetrapeptide amide common to both gastrin and CCK was found. The results indicate that true gastrin as well as CCK are present in CSF, and that both hormones display a molecular heterogeneity similar to that found in extracts of brain tissue.