Stimulation of cholecystokinin (CCK) release from superfused rat hypothalamo-neurohypophyseal complexes by interleukin-1 (IL-1)

Evidence for suppression of electroacupuncture on spinal glial activation and behavioral hypersensitivity in a rat model of monoarthritis

Our previous study demonstrated that single intrathecal (i.t.) application of fluorocitrate, a glial metabolic inhibitor, synergized electroacupuncture (EA) antagonizing behavioral hypersensitivity in complete Freund's adjuvant (CFA)-induced monoarthritic rat. To further investigate the relationship between spinal glial activation and EA analgesia, the present study examined the effects of multiple EA on spinal glial activation evoked by monoarthritis (MA). The results showed that (1) unilateral intra-articular injection of CFA produced a robust glial activation on the spinal cord, which was associated with the development and maintenance of behavioral hypersensitivity; (2) multiple EA stimulation of ipsilateral "Huantiao" (GB30) and "Yanglingquan" (GB34) acupoints or i.t. injection of fluorocitrate (1 nmol) significantly suppressed spinal glial activation; (3) inhibitory effects of EA on spinal glial activation and behavioral hypersensitivity were significantly enhanced when EA combined with fluorocitrate, indicating that disruption of glial function may potentiate EA analgesia in inflammatory pain states. These data suggested that analgesic effects of EA might be associated with its counter-regulation to spinal glial activation, and thereby provide a potential strategy for the treatment of arthritis.

Glia: novel counter-regulators of opioid analgesia

Development of analgesic tolerance and withdrawal-induced pain enhancement present serious difficulties for the use of opioids for pain control. Although neuronal mechanisms to account for these phenomena have been sought for many decades, their bases remain unresolved. Within the past four years, a novel non-neuronal candidate has been uncovered that opposes acute opioid analgesia and contributes to development of opioid tolerance and tolerance-associated pain enhancement. This novel candidate is spinal cord glia. Glia are important contributors to the creation of enhanced pain states via the release of neuroexcitatory substances. New data suggest that glia also release neuroexcitatory substances in response to morphine, thereby opposing its effects. Controlling glial activation could therefore increase the clinical utility of analgesic drugs.

The effect of lipopolysaccharide on cholecystokinin in murine plasma and tissue

Several mechanisms have been proposed for neuroimmune communication supporting sickness behavior (fever, anorexia, inactivity, and cachexia) following infection. We examined the role of cholecystokinin as a neurochemical intermediary of sickness behavior by determining plasma, duodenum, hypothalamus, and brainstem cholecystokinin concentrations 30 and 60 min and 12 h following intraperitoneal lipopolysaccharide (LPS) (0.25 and 2.5 mg/kg). Hypothalamic cholecystokinin was significantly lower in LPS- versus saline-treated mice 30 min (0.25 and 2.5 mg/kg) and 12 h (2.5 mg/kg) post-injection. Plasma cholecystokinin of LPS-treated mice was significantly lower than that of controls 1 and 12 h post-injection, a finding consistent with a non-endocrine action of peripheral cholecystokinin.

CCK-8 and PGE1: central effects on circadian body temperature and activity rhythms in rats

Cholecystokinin-octapeptide (CCK-8) has been shown to possess an acute thermogenic and hyperthermic action when given intracerebroventricularly in slightly restrained rats. To substantiate the febrile nature of that hyperthermia freely moving animals should be used and together with body core temperature, at least one behavioral parameter, such as general activity, should also be recorded. In the present studies, Wistar rats (N=34) exposed to thermoneutral (26-28 degrees C) or cold (4 degrees C) ambient temperature and to a 12:12-h light/darkness schedule were infused intracerebroventricularly with CCK-8 or prostaglandin E1 (PGE1) for several days using ALZET minipump and changes in body core temperature and general activity were recorded by biotelemetry (Minimitter). In rats exposed to a thermoneutral ambient temperature, low doses of CCK-8 induced slight but significant rises of day minima of circadian body temperature rhythm (CBTR) and with a high dose (1 microg/h) of the peptide--infused either at thermoneutrality or during cold exposure--an increase of acrometron could also be recorded. All of these changes were observed only during the first 2-4 days of 7-day-long infusions. Intracerebroventricular infusion of PGE1 administered at thermoneutrality in a dose of 1 microg/h for 7 days induced a marked rise in body core temperature with a disappearance of CBTR in some rats for 2-3 days or with rises of day minima/acrometron in others. General activity--running parallel with CBTR in periods without infusions--tended to be decreased when core temperature rose during the first couple of days of intracerebroventricular infusion of higher doses of CCK-8 or of PGE1. The decreased general activity--one component of sickness behavior--together with an increased body core temperature found in the present study, supports the view that they are components of a genuine fever induced by the central effect of the two mediators used.

Plasma concentrations of interleukin-1-beta, interleukin-6 and tumor necrosis factor-alpha, and of their soluble receptors and receptor antagonist in anorexia nervosa

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) induce anorexia, and multiple behavioral and biochemical alterations that mimic those of anorexia nervosa. Reports in the literature, however, contain contrasting data on the pattern of secretion of the three cytokines and on the downstream activities of their receptors and receptor antagonists in anorexia nervosa. We measured plasma concentrations of IL-1beta, IL-6, TNF-alpha, soluble IL-6 receptor (sIL-6-R), soluble TNF-alpha receptors I and II (s-TNF-alpha-R-I and II), and soluble IL-1beta receptor antagonist (s-IL-1beta-R-A) in 14 female patients with anorexia nervosa (nine restricters, five binge/purgers) and in 13 age- and sex-matched healthy control subjects to see whether the circulating cytokine concentrations and the downstream steps of cytokine activity were impaired, and if these alterations were correlated with some aspects of the disease. Concentrations of IL-1beta, IL-6, TNF-alpha, s-TNF-alpha-R-I and -II and sIL-1beta-RA in plasma did not differ significantly in patients with anorexia nervosa compared with control subjects. Concentrations of sIL-6-R were significantly lower in the patients than in the control subjects, but there were no differences between the two sub-types of anorexia nervosa. The etiopathogenetic significance of the sIL-6-R alteration is not clear, but together with recent data in the literature on cytokine function, the finding suggests that an impairment of the pro-inflammatory cytokine pathway might be involved in the development of anorexia nervosa.

Cholecystokinin and thermoregulation--a minireview

Thermoregulatory effects of cholecystokinin (CCK) peptides are reviewed with special emphasis on two types of responses, that is hypothermia or hyperthermia. In rodents exposed to cold a dose-dependent hypothermia has been observed on peripheral injection of CCK probably acting on CCKA receptors. Central microinjection of CCK in rats induced a thermogenic response that could be attenuated by CCKB receptor antagonists, but some authors observed a hypothermia. It is suggested that neuronal CCK may have a specific role in the development of hyperthermia, and endogenous CCK-ergic mechanisms could contribute to the mediation of fever. Possible connections between thermoregulatory and other autonomic functional changes induced by CCK are discussed.

Conjugated linoleic acid: implications for human health

Conjugated linoleic acid (CLA) is being sold as a panacea that has the capability of reducing or eliminating cancer, preventing heart disease, improving immune function, and altering body composition to treat obesity or build lean body mass. Unfortunately, there has been very little published human research on CLA. This review will examine the literature on CLA and discuss the animal research on which the above claims are made. The limited human studies will be presented with an evaluation of the potential uses of CLA for human health and disease.

Cholecystokinin receptors do not mediate the suppression of food-motivated behavior by lipopolysaccharide and interleukin-1 beta in mice

During the course of an infection, profound metabolic and behavioral changes are observed. The resulting decrease in food intake can be reproduced by administration of lipopolysaccharide (LPS) or the proinflammatory cytokines (e.g., interleukin-1 [IL-1] and tumor necrosis factor it induces. To test the possibility that cholecystokinin (CCK) mediates anorexia induced by IL-1 beta and LPS, mice trained to poke their noses in a hole to obtain a food reward according to a fixed ratio (1 reward per 20 actions) were pretreated with the CCK-A receptor antagonist L364,718 (at 1 mg/kg) or with the CCK-B receptor antagonist L365,260 (50 microg/kg) before being injected with LPS (100 microg/kg) or IL-1 beta (20 microg/kg). All injections were given via the intraperitoneal (i.p.) route. In spite of its ability to block the effects of exogenous CCK-8 on food-motivated behavior in mice, the CCK-A receptor antagonist did not block the depressive actions of LPS and IL-1 beta on food-motivated behavior. The CCK-B receptor antagonist was not more effective at blocking. These results do not support a role for CCK in the anorexic effect of LPS and IL-1 beta.

Differential effects of lipopolysaccharide and cholecystokinin on sucrose intake and palatability

The differential effects of CCK and lipopolysaccharide (LPS) on sucrose intake and palatability were examined. Rats were injected with LPS (200 microg/kg ip) or NaCl (0.9%, vehicle) and 2 h later received a second injection of either CCK (8 microg/kg ip) or NaCl. In experiment 1, sucrose (0.3 M) intake was monitored for 1 h on three different test days 72 h apart, while in experiment 2, palatability was assessed by means of the taste reactivity test (TRT) on two separate days (72 h apart). In the TRT, orofacial and somatic responses to brief (30 s) intraoral infusions of sucrose were recorded and analyzed for response frequency. Singly, LPS and CCK reduced sucrose intake, with a more pronounced effect from combined LPS and CCK. LPS by itself did not alter sucrose palatability, as evidenced by continuous high levels of ingestive responding. In contrast, CCK-treated rats displayed a pattern of responding indicative of satiety, as did the combined LPS-CCK-treated rats. These results suggest that LPS does not induce hypophagia by altering palatability.

Nutritional effects on vaccination

Immune-induced cachetic response is an example of a biological opportunity to develop technologies that ensure improved performance in animal agriculture. We have estimated that reduced performance of immune stimulated animals, whether by exposure to conventional environments or through vaccination, results in more than U.S. $500 million in reduced productivity. Nontraditional methods to alleviate the adverse effects of the immune response provide an opportunity for those skilled in the art of vaccinology and immunology to develop new technologies and feeding practices. Too often, biologists are blinded by the limits of their disciplines and rarely venture to the fringe of their field to engage in collaborations that at first glance do not seem logical. The examples of CLA and antigastrointestinal peptides suggest that new opportunities await in ensuring that the cost of the immune response is minimized and that new approaches to animal agriculture await discovery.

Interaction of cholecystokinin and somatostatin with a selective mu-opioid agonist and mu- and kappa-antagonists in thermoregulation

We examined the effects of intracerebroventricular (i.c.v.) injections of cholecystokinin-octapeptide (CCK-8) and somatostatin (SST) and the interactions of these neuropeptides with the selective opioid antagonists, CTAP (mu) and nor-BNI (kappa) and the mu-agonist, PL017, on body temperature (Tb) of the rat at normal ambient temperature (21 +/- 0.5 degrees C). CCK-8 produced short-lasting (15-60 min), dose-related increases in Tb in a dose range of 20 to 900 ng but did not change the Tb at lower doses (0.1-2 ng). Lower doses of SST (1 and 2 micrograms) produced hyperthermia (30-60 min) and a higher dose of SST (10 micrograms) caused hypothermia (30-45 min). PL017 (1 microgram, i.c.v.), alone and in combination with CCK-8, produced hyperthermia. The CCK-8 (300 ng)-induced hyperthermia was blocked by pretreatment of rats with CTAP (1 microgram, i.c.v.), suggesting that the higher doses of CCK-8 increase Tb through the interaction with mu-receptors or the enhancement of release of endogenous opioids acting on the mu-receptor. The hyperthermia elicited by a lower dose of SST (1 microgram) was prevented by pretreatment with CTAP but not with nor-BNI (1 microgram, i.c.v.). Pretreatment with nor-BNI blocked the higher dose (10 micrograms) of SST-induced hypothermia. PL017 or CTAP did not prevent the hypothermic effect of that dose of SST. These results indicate that a lower dose of SST (1 microgram) stimulates the mu-receptor (directly or indirectly) and a higher dose (10 micrograms) interacts with the kappa-receptor in regulation of Tb. Thus, the effects of both CCK-8 and SST on Tb appear to involve the endogenous opioid system.

Effects of substance P and selected other neuropeptides on the synthesis of interleukin-1 beta and interleukin-6 in human monocytes: a re-examination

Recent studies have suggested that substance P (SP) and some other neuropeptides are able to induce the synthesis of the proinflammatory cytokines interleukin-1 (IL-1) and interleukin-6 (IL-6) in peripheral blood mononuclear cells. In the present study, we re-examined these findings by using a completely endotoxin-free monocyte cultivation system. We demonstrate that the neuropeptides SP, vasoactive intestinal peptide, substance K. cholecytokinine, alpha-endorphin and beta-endorphin are consistently unable to induce the synthesis of IL-1 and IL-6 in human peripheral blood monocytes. However, low amounts of LPS (1 pg/ml) synergized with SP to induce IL-6 mRNA expression. In contrast to its lack of effect in monocytes, we were able to confirm the ability of SP to induce cytokine synthesis in astrocytic cells. Our results raise questions about previous results claiming a neuropeptide-induced synthesis of proinflammatory cytokines in human monocytes. In conjunction with other studies, we suggest that undetected levels of endotoxin/LPS in the culture medium may have been primarily responsible for results suggesting an inductive effect of neuropeptides on cytokine synthesis in monocytes.

Cholecystokinin octapeptide (CCK-8) injected into a cerebral ventricle induces a fever-like thermoregulatory response mediated by type B CCK-receptors in the rat

In conscious female Wistar rats with chronic lateral cerebroventricular cannula, the thermoregulatory effects of CCK-8, ceruletide and prostaglandin E1 (PGE1) were studied. In addition, the possible involvement of type A or type B receptors of CCK-8 in thermoregulatory effects of PGE1 and CCK-8 was also investigated. In the normothermic rat an intracerebroventricular (i.c.v.) injection of CCK-8 or ceruletide induced a thermogenic response with tail-skin vasoconstriction and a resulting rise in colonic temperature (Tc). There was a significant negative correlation between the starting level of Tc and the extent of rise in Tc following an i.c.v. administration of PGE1, CCK-8 or ceruletide. Subcutaneously injected CCK-8 caused decreases in Tc in a cool ambient temperature as also described by others. The fever-like response to i.c.v. injected CCK-8 was attenuated by a CCK type B receptor blocker, but not by a CCK type A receptor blocker. Conversely, the hypothermic response to peripherally administered CCK-8 was attenuated by a type A receptor blocker, but not by a type B receptor blocker. Neither of these CCK-receptor blockers influenced the fever caused by an i.c.v. injection of PGE1. It is concluded that in normothermic rats the thermogenic response observed after i.c.v. injection of CCK-8 and ceruletide is the most likely central thermoregulatory change mediated by CCK type B receptors, while the well-known hypothermic response observed after peripheral injection of these peptides might also be explained by their direct effect on variables influencing some of the thermoregulatory effector mechanisms at the periphery.