CCK-containing Neurons Research Articles

The Excitatory Effect of Cholecystokinin on Colonic Motor Function via Cholecystokinin Receptor

Cholecystokinin (CCK) was first described over 70 years ago as a putative hormone that caused gallbladder contraction in response to fat in the small intestine.1 The actions of CCK include stimulation of exocrine and endocrine secretion, motility and growth in the gastrointestinal tract, and regulation of satiety, anxiety, pain and behavior in the central and peripheral nervous systems. It is therefore a prototype of a class of agents known as brain-gut peptides, functioning both as a neuropeptide and as a gut hormone.2,3 There are 2 principal sources of CCK: endocrine I cells in the duodenal wall that are in contact with the lumen of the intestine, and peptidergic nerves both in the enteric nervous system and in the central nervous system. In the periphery, CCK-containing neurons are found in the myenteric plexus, submucosal plexus, muscle layers of the small intestine and colon, the celiac plexus and the vagus nerve.4 Receptors for CCK were first characterized on pancreatic acinar cells and identified as CCK type A receptors (CCK-A or CCK1), with the subsequent discovery in the same year of a second receptor with a different pharmacology in the brain, CCK type B receptors (CCK-B or CCK2). These 2 types of CCK receptor could be pharmacologically distinguished on the basis of their affinity for the agonists CCK and gastrin. CCK1 are highly selective for analogs of CCK, whereas CCK2 have similarly high affinity for both analogs of CCK and gastrin.5 CCK has been known to affect human colonic motility for more than 3 decades.6 In spite of the large number of functional investigations since then, only 1 study has provided data regarding the distribution of CCK1 receptors in human colon.7 It is well known that CCK affects colonic motility by 2 fundamentally different pathways: acting on neurons in the myenteric plexus and directly on the smooth muscle cells. Cholinergic regulation is involved in the pathway acting on neurons. Interestingly, it was suggested that CCK stimulate the release of peptide YY (PYY) which increases the colonic motility in rat colon.8 However, there are no crucial reports whether CCK act on colonic motility by regulating cholinergic neurons or stimulating the release of PYY. In this issue of the Journal of Neurogastroenterology and Motility, Ko et al investigated the effects of CCK on colonic motility, the involvement of PYY release and cholinergic regulation on CCK-induced action in isolated, vascularly perfused rat colon. They found that CCK increased the colonic motility in proximal and distal colon dose-dependently. Also, they could see the increasing effect on colonic motility. To find the CCK receptor subtype, they used loxiglumide, a specific CCK1 receptor antagonist and found loxiglumide blocked the CCK-induced action on colonic motility. In previous reports, there are many suggestions that CCK1 receptor only involves for CCK action in colon, gallbladder, pancreas and stomach of animals and human.9,10 There is a thread of connections between previous reports and this result. And they could find CCK to stimulate the release of PYY in proximal and distal colon dose-dependently. Furthermore, CCK- or PYY-induced action on colonic motility was inhibited by pretreatment with atropine. These mean that CCK can act on colonic motility by stimulating PYY release or by cholinergic pathway. Interestingly, it was already suggested that the release of PYY could be stimulated by CCK or cholinergic regulation in proximal colon whereas by direct mechanism in distal colon.9 So, they concluded that CCK1 receptor, PYY release and cholinergic input are closely related with CCK-induced action on colonic motility. The acting mechanism of CCK on colonic motility appears more intricate because of the wide-spread localization in gastrointestinal tract. Therefore, finding the exact mechanism of CCK-induced action on gastrointestinal motility must be further studied in the future.

Cholecystokinin expression after hippocampal deafferentiation: molecular evidence revealed by differential display-reverse transcription–polymerase chain reaction

The cortical information flow via the perforant path represents a major excitatory projection to the hippocampus. Lesioning this projection leads to massive degeneration and subsequently to reorganization in its termination zones as well as in primary non-affected subfields of the hippocampus. The molecular mechanisms and factors which are involved in the postlesional events are poorly defined. Using a differential display reverse transcription–polymerase chain reaction (DDRT-PCR) strategy, we located one band which occurred only in control hippocampus lanes and almost disappeared in the lanes of lesioned hippocampi. By sequencing, we identified the corresponding gene as cholecystokinin (CCK). Northern blot analysis confirmed a decreased transcription of CCK after lesion. In situ hybridization analysis was performed for localization and quantification of altered CCK transcription. We noted a significant downregulation of CCK transcription in the hippocampus (20%) and in the contralateral cortex (12%) 1-day after lesion (dal) and an increased signal in the ipsilateral cortex (10.5%). This pattern was altered, showing upregulation of CCK mRNA expression, reaching its highest level of 70% above control levels at 5 dal. In the hippocampus, the control level was reached again at 21 dal, whereas the cortex reached the control level at 10 dal. In comparison, the mRNA transcripts of the receptors CCK A and CCK B remained unchanged. Since CCK-containing neurons are involved in the modulation of pyramidal and granule cell excitability, our data indicate a time course correlation between CCK mRNA expression and postlesional axonal sprouting response in the hippocampus.

Cholecystokinin Innervation of the Cerebral Cortex in a Reptile, the Lizard Psammodromus algirus

We used light and electron microscopic and immunohistochemical methods to map the distribution of cholecystokinin (CCK) in the cerebral cortex of a lizard, Psammodromus algirus. At light microscopy, the CCK immunoreactivity was limited to fibers and terminals densely innervating all cortical regions except for the lateral (pyriform) cortex which was very slightly immunostained. The CCK-positive terminals were almost restricted to the cell layers in every cortical region where they surrounded immunonegative cell bodies and proximal dendrites of neurons within the layer. No CCK-containing neurons were observed within the cerebral cortex. At the electron microscopic level, most positive structures were presynaptic boutons contacting cell bodies and proximal dendrites. All contacts appeared to form symmetric junctions. both the distribution and type of synaptic contacts of CCK fibers in the cerebral cortex of Psammodromus are very similar to the corresponding features in the hippocampus of mammals, although in this lizard the CCK cortical innervation, unlike that in mammals, is probably of extrinsic origin. Double HRP-retrograde labeling and CCK immunohistochemistry show that part of the CCK in the cerebral cortex of Psammodromus arises from the hypothalamic supramammillary nuclei.

Effect of Methamphetamine and Dopamine Receptor Antagonists on Cholecystokininlike Immunoreactivity in the Rat Medial Prefrontal Cortex

A single intraperitoneal administration of methamphetamine (MAP) reduces cholecystokininlike immunoreactivity (CCK-LI) in medial prefrontal cortex (mPFC) of the rat brain. This report examines the effects of various dopamine (DA) receptor antagonists [haloperidol (HAL), sulpiride (SUL), YM09151-2 (YM), and SCH23390 (SCH)] on MAP-induced abnormal behaviors and the changes of CCK-LI in the rat mPFC. A single subcutaneous administration of HAL (0.25 mg/kg), YM (0.1 mg/kg), or SUL (250 mg/kg) significantly reduced the basal CCK-LI in mPFC by 20–40%; a selective D 1 antagonist, SCH (up to 1.0 mg/kg), had no effect on basal CCK-LI. However, the reduction of CCK-LI induced by MAP (20–40%) was abolished by the pretreatment with HAL (0.025 and 0.25 mg/kg), YM (0.01 and 0.1 mg/kg), or SCH (1.0 mg/kg), without being affected by SUL (up to 250 mg/kg). This effect of DA antagonists on MAP-induced change in CCK-LI was associated with an inhibition of MAP-induced stereotyped behaviors. These data suggest that the CCK-containing neurons in rat mPFC are functionally related to the mesocortical DA system and may participate in a development of abnormal behaviors induced by MAP.

Opioid control of the spinal release of cholecystokinin (CCK) in morphine-tolerant and non-tolerant rats

The K +-evoked release of cholecystokinin (CCK)-like material (CCKLM) from spinal cord slices of naive or placebo-treated rats was found to be under complex opioid control (inhibited by the activation of μ or one subtype of ∂ receptors, and enhanced by the activation of another ∂ receptor subtype), while the release from morphine-tolerant rats was only under the stimulatory influence of a ∂-dependent mechanism. Morphine itself exerted a biphasic effect (inhibitory at low concentrations through the activation of μ receptors, and stimulatory at a high concentration, 10 μM, through the activation of ∂ receptors) on spinal CCKLM release in control (naive or placebo-treated) rats, and only a stimulatory effect (at 10 μM) in morphine-tolerant rats. These data indicate that in morphine-tolerant rats opioids retain only their excitatory influence on spinal CCK-containing neurons, in line with the hypothesis that CCK release may be enhanced by chronic morphine treatment.

Disappearance of the inhibitory but not of the excitatory effects of opioids on spinal CCK-containing neurons in morphine-tolerant rats

Disappearance of the inhibitory but not of the excitatory effects of opioids on spinal CCK-containing neurons in morphine-tolerant rats

Opioid control of the in vitro release of cholecystokinin-like material from the rat substantia nigra.

Possible interactions between Met-enkephalin and cholecystokinin (CCK)-containing neurons in the rat substantia nigra were investigated by looking for the effects of various opioid receptor ligands and inhibitors of enkephalin-degrading enzymes on the K(+)-evoked overflow of CCK-like material (CCKLM) from substantia nigra slices. The delta-opioid agonists D-Pen2, D-Pen5-enkephalin (50 microM) and Tyr-D-Thr-Gly-Phe-Leu-Thr (DTLET; 3 microM) enhanced, whereas the mu-opioid agonists Tyr-D-Ala-Gly-MePhe-Gly-ol (DAGO; 10 microM) and MePhe3, D-Pro4-morphiceptin (PL 017; 10 microM) decreased, the K(+)-evoked release of CCKLM. By contrast, the kappa-opioid agonist U-50488 H (5 microM) was inactive. The stimulatory effect of DTLET could be prevented by the delta antagonist ICI-154129 (50 microM), but not by the mu antagonist naloxone (1 microM). Conversely, the latter drug, but not ICI-154129, prevented the inhibitory effect of DAGO and PL 017. A significant increase in CCKLM overflow was observed upon tissue superfusion with the peptidase inhibitors kelatorphan or bestatin plus thiorphan. This effect probably resulted from the stimulation of delta-opioid receptors by endogenous enkephalins protected from degradation, because it could be prevented by ICI-154129 (50 microM). Furthermore the peptidase inhibitors did not enhance CCKLM release further when delta-opioid receptors were stimulated directly by DTLET (3 microM). These data indicate that opioids acting on delta and mu receptors may exert an opposite influence, i.e., excitatory and inhibitory, respectively, on CCK-containing neurons in the rat substantia nigra.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of intraperitoneally administered phencyclidine on the central nervous system: Behavioral and neurochemical studies

The effects of intraperitoneally (IP) injected phencyclidine (phencyclohexyl piperidine; PCP) on the metabolism of dopamine (DA) and cholecystokinin-like immunoreactivity (CCK-LI) in the rat brain were investigated in connection with PCP-induced behavioral changes. The predominant behavior change elicited by 2.5 mg/kg PCP was locomotion, while with higher doses (5 and 10 mg/kg) sniffing, swaying and falling were observed in addition to the enhanced locomotor activity. Backpedaling and rotation were observed in 10 mg/kg PCP-treated rats. IP injection of PCP caused a dose-related increase in the levels of DA and 3,4-dihydroxy-phenylacetic acid (DOPAC) in the medial frontal cortex (MFC) and anterior cingulate cortex (ant.CC) without any changes in the nucleus accumbens (NAc) or striatum. CCK-LI in the MFC, ant.CC and NAc was decreased in a dose-dependent manner following IP injection of PCP. These findings support the evidence that PCP selectively activates the mesocortical DA systems. Furthermore, our results indicate a functional relationship between the mesocortical DA neurons and intrinsic CCK containing cortical neurons, and the change in the activity of the intrinsic CCK-containing cortical neurons in these two areas, perhaps due to an alteration in DA transmission, might be involved in behavioral changes after PCP injection.

Antiserum raised against residues 159-168 of the guanine nucleotide-binding protein Gi3-alpha reacts with ependymal cells and some neurons in the rat brain containing cholecystokinin- or cholecystokinin- and tyrosine 3-hydroxylase-like immunoreactivities.

Antibodies raised against a synthetic deca-peptide corresponding to a specific sequence of Gi3-alpha protein (an inhibitory guanine nucleotide-binding protein) were used to analyze Gi3-alpha-like immunoreactivity in brain sections from colchicine-treated rats by indirect immunofluorescence histochemistry. Gi3-alpha-peptide-positive cell bodies were found in the ventral tegmental area and substantia nigra, and these cells were also cholecystokinin (CCK)- and tyrosine 3-hydroxylase-positive. Gi3-alpha-peptide staining was observed in perikarya in the hippocampus and in fibers in the nucleus accumbens, tuberculum olfactorium, bed nucleus of stria terminalis, and a spino-thalamic tract, where it coexisted with CCK-like immunoreactivity as well. No coexistence with CCK occurred in Gi3-alpha-peptide-positive ependymal cells outlining the aqueduct and ventricles. Preadsorption of Gi3-alpha antibodies with CCK-8 or CCK-33 did not alter Gi3-alpha-peptide staining. The occurrence of Gi3-alpha-peptide-like immunoreactivity in CCK-containing neurons may indicate the presence of Gi3-alpha protein and in CCK/dopamine neurons may indicate an association of this Gi protein with dopamine autoreceptors.

Differential distributions of cholecystokinin in hamster and rat forebrain

Rats and golden hamsters show a differential feeding response to intracranial injections of cholecystokinin (CCK). Rats, but not hamsters reduce food intake after CCK injections into the hypothalamic paraventricular nucleus. In view of this species difference, we undertook an immunohistochemical study of the distribution of CCK-immunoreactivity in the hamster hypothalamus and remaining forebrain. CCK-immunoreactive perikarya were abundant in the neocortex, claustrum, hippocampal formation, amygdaloid complex, bed nucleus of the stria terminalis, nucleus of the lateral olfactory tract and in the magnocellular basal nucleus. CCK-immunoreactive neurons had a more restricted distribution in the diencephalon and were relatively rare in the preoptic area-hypothalamus. The only exception was the suprachiasmatic nucleus and adjacent medial anterior hypothalamus, in which CCK-immunoreactive neurons were numerous. CCK-containing perikarya were not observed in the hamster hypothalamic paraventricular and supraoptic nuclei, where they have been reported to occur in the rat. Groups of CCK-positive perikarya were also noted in the hamster thalamic paratenial and parafascicular nuclei. CCK-immunoreactive fibers/terminals were localized in the caudate and putamen, periventricular zones, dorsolateral geniculate, thalamic reticular nucleus and the superficial layer of the optic tectum. Fiber/terminal labeling was also present in those regions associated with CCK-immunoreactive perikarya. Our results indicate that the telencephalic distribution of CCK-containing neurons in the hamster appears to be similar to that reported in the rat. However, several differences occur in the diencephalon. Perhaps the most striking is that the hamster differs from the rat in having a large group of CCK-containing neurons in the suprachiasmatic nucleus, and in lacking the CCK-containing perikarya observed in the rat paraventricular and supraoptic nuclei. These differences may underly species differences in feeding responses to intracranial CCK injections and gonadal responses to short photoperiods. Our data further suggest that the distribution of neuropeptides and other neuroactive substances may not always be conserved during evolution.

Neuronal cholecystokinin release: morphine and naloxone effects on rat periaqueductal grey

The periaqueductal grey area (PAG) of rat brain is strongly indicated as a major site of opiateand stimulation-induced analgesia. The PAG is thought to integrate perception and response to nociceptive stimuli; afferent projections include major imputs from limbic and sensory areas; efferent projections include those to the spinal cord and nucleus raphe magnus (Beitz, 1982). Apart from its content of opioid peptides, the PAG also contains cholecystokinin octapeptide (CCK), which may be involved in processing of nociceptive stimuli since it reverses morphine-, /I-endorphinand footshock-induced analgesia (Faris et al., 1983). Furthermore, at higher doses CCK is an antinociceptive agent in its own right (Jurna & Zetler, 1981; Sheehan & de Belleroche, 1984). A further indication of a possible interaction between CCK and opiate analgesia systems at the level of the PAG is the finding that the firing of CCK neurons in the EdingerWestphal nucleus of the PAG is reduced by noxious stimuli or intravenous morphine (Innis & Aghajanian, 1985). The following experiments were designed to ascertain whether there is a direct action of opiates on CCKcontaining neurons in the PAG as measured by CCK release. Male CFY rats were killed, their brains removed and the PAG dissected out and chopped (tissue slices 0.3mm thick). The slices were incubated at 37°C in Krebs-bicarbonate medium, pH 7.4, containing 0.5 mMbacitracin and gassed with 95% 0 , / 5 % CO,. After one 10 min preincubation the slices were sequentially transferred to drug-containing medium for a further IOmin, to evaluate basal release and then, for another 5 min, to a third chamber containing the drug plus high K + ion concentration (34 mM) to evoke neurotransmitter release. After incubation, tissue slices were placed in 90% CH30H/IO% H,O, O'C, and sonicated to extract low molecular weight forms of CCK. The methanolic extracts were dried under nitrogen and rehydrated before assay. The supernatants from the incubation vials were frozen until used for assay. Tissue and released levels of CCK were measured by radioimmunoassay with antisera Ab2717 (a generous gift from Professor J. Rehfeld) against monoiodinated human gastrin (2-17) as a tracer. Tissue slices were exposed to morphine hydrochloride ( 10-'0-10-' M) or naloxone hydrochloride ( l o ' 1 0 6 ~ ) . Two Caz+ ion concentrations were used for the experiments with morphine, 0.6 mM or 2.5 mM, to evaluate whether any morphine action was Ca2+ dependent.

The effect of neonatal anoxia on brain cholecystokinin-8-like immunoreactivity and monoamine levels of mature rats

The effect of neonatal anoxia upon cholecystokinin-8-like immunoreactivity (CCK-8-I) concentrations was investigated in different brain areas of mature rats. Anoxia within 24 h after birth resulted in significantly lower CCK-8-I levels in the cortex, nucleus accumbens, amygdala and hypothalamus of 10-week-old rats. In contrast, no change was observed in the monoamine levels of these brain areas. The data suggest that neonatal anoxia selectively affects CCK-containing neurons.

Cholecystokinin-containing and nociceptive neurons in rat edinger-westphal nucleus

The putative peptide neurotransmitter cholecystokinin (CCK) is co-localized witsubstance P (SP) in a dense cluster of neurons located in the rat Edinger-Westphal (EW) nucleus. In an attempt to record electrophysiologically from these CCK-containing neurons, we have identified a group of nociceptive neurons located within the confines of the EW nucleus. The firing pattern of these nociceptive neurons is erratic, sometimes wita bursting pattern and at other times witfairly regular rates whicvary generally from 1 to 7 Hz. These neurons respond to noxious stimuli, sucas toe pinch, witan increase in rate and sometimes enter an apparent depolarization blockade (preceded by an increase in the duration and a decrease in the amplitude of the action potential). Systemically administered morphine suppresses botthe spontaneous firing rate and the toe pinch-induced increase in firing rate. Naloxone is able to reverse the effects of morphine. Althougwe have identified in the EW area a moderate density of terminals containing enkephalin-like immunoreactivity, morphine locally applied via microiontophoresis is largely without effect on the firing of these neurons. We hypothesize that the opiate-induced suppression of these nociceptive neurons is not mediated directly on the EW cells, but rather indirectly througafferent systems.

Corticotropin releasing factor-like immunoreactivity in sensory ganglia and capsaicin sensitive neurons of the rat central nervous system: Colocalization with other neuropeptides

Immunohistochemistry and radioimmunoassay (RIA) revealed that corticotropin releasing factor (CRF)-like immunoreactivity was found to be colocalized with substance P (SP)-, somatostatin (SST)- and leu-enkephalin (LENK)-like immunoreactivity in the dorsal root-and trigeminal ganglia, the dorsal horn of the spinal cord (laminae I and II), the substantia gelatinosa, and at the lateral border of the spinal nucleus and in the tractus spinalis of the trigeminal nerve. These peptides were also located in fast blue labeled cells of the trigeminal ganglion following injection of the dye into the spinal trigeminal area. This indicates that there are possible sensory projections of these peptides into the spinal trigeminal area. Capsaicin treatment of neonatal rats resulted in a marked decrease in the density of CRF-, SP-, VIP- and CCK-containing neurons in the above mentioned hindbrain areas, whereas SST- and LENK-immunoreactivity were not changed. RIA revealed that, compared to controls, CRF, SP and VIP concentrations in these areas were decreased in rats pretreated with capsaicin, while SST levels were increased; CCK and LENK levels were unchanged. It is concluded that the primary afferent neurons of the nucleus and tractus spinalis of the trigeminal nerve are richly endowed with a number of peptides some of which are sensitive to capsaicin action. The close anatomical proximity of these peptide containing neurons suggests the possibility of a coexistance of one or more of these substances.

Extra-hippocampal projections of CCK neurons of the hippocampus and subiculum

A population of neurons in the hippocampus and subiculum contains cholecystokinin (CCK). Following transection of the dorsal fornix, a major afferent pathway of the hippocampus and associated structures, CCK levels were reduced in the septum and hypothalamus. A microdissection analysis indicated that the loss of CCK occurred in nuclei receiving direct projections from the hippocampus and subiculum, suggesting that CCK-containing neurons in the hippocampus and subiculum project to extrahippocampal regions.