Individual differences in the feeding response to CCKB antagonists: role of the nucleus accumbens

Control of Food Intake by Gastrointestinal Peptides: Mechanisms of Action and Possible Modulation in the Treatment of Obesity

This review focuses on the control of appetite by food intake-regulatory peptides secreted from the gastrointestinal tract, namely cholecystokinin, glucagon-like peptide 1, peptide YY, ghrelin, and the recently discovered nesfatin-1 via the gut-brain axis. Additionally, we describe the impact of external factors such as intake of different nutrients or stress on the secretion of gastrointestinal peptides. Finally, we highlight possible conservative—physical activity and pharmacotherapy—treatment strategies for obesity as well as surgical techniques such as deep brain stimulation and bariatric surgery also altering these peptidergic pathways.

Peripheral signals modifying food reward

The pleasure derived from eating may feel like a simple emotion, but the decision to eat, and perhaps more importantly what to eat, involves central pathways linking energy homeostasis and reward and their regulation by metabolic and endocrine factors. Evidence is mounting that modulation of the hedonic aspects of energy balance is under the control of peripheral neuropeptides conventionally associated with homeostatic appetite control. Here, we describe the significance of reward in feeding, the neural substrates underlying the reward pathway and their modification by peptides released into the circulation from peripheral tissues.

Reduced CCK-induced Fos expression in the hindbrain, nodose ganglia, and enteric neurons of rats lacking CCK-1 receptors

Many of the actions of cholecystokinin (CCK) are mediated by CCK-1 receptors, expressed by enteric and vagal afferent neurons. Otsuka Long-Evans Tokushima Fatty rats (OLETF) do not express CCK-1 receptors, and do not exhibit the vagally mediated responses to CCK. To determine whether the OLETF rat's failure to respond to CCK is correlated with failure of CCK to activate enteric and vagal neurons, we quantified neuronal Fos immunoreactivity in the dorsal vagal complex of the hindbrain, the nodose ganglia, and the ganglia of the myenteric and submucosal plexuses of the duodenum following intraperitoneal injection of CCK-8 (20 microg/kg). Compared to vehicle injection, CCK administration resulted in significant increases in the number of Fos-immunopositive neurons in the nucleus of the solitary tract, area postrema, and dorsal vagal motor nucleus of control, LETO rats. In OLETF rats, however, CCK did not increase numbers of Fos-immunoreactive neurons in any of these brain structures. CCK also induced significantly larger numbers of Fos-immunoreactive neuronal nuclei in the nodose ganglia of LETO rats, but not in the nodose ganglia of OLETF rats. Finally, LETO, but not OLETF rats exhibited striking increases in the number of Fos-immunoreactive nuclei of myenteric and submucosal neurons, following CCK injection. Absence of CCK-induced Fos expression in OLETF rats is consistent with attenuation of ingestive and gastrointestinal responses to CCK in the CCK-1 receptor deficient rats. These results also suggest that CCK-induced Fos expression in enteric and vagal sensory neurons of rats can be accounted for entirely by activation of CCK-1 receptors and is not due to occupation of CCK-2 (gastrin) receptors, which also are expressed in the intestine and by some vagal afferent neurons.

Excitotoxic lesions of the lateral parabrachial nucleus do not prevent cholecystokinin-induced suppression of milk intake in rats

We examined the effect of lateral (visceral) and medial (gustatory) parabrachial nucleus (PBN) lesions on the suppression of milk intake induced with cholecystokinin (CCK) in 24 h food-deprived rats. Irrespective of CCK dose, each type of PBN lesion significantly elevated the consumption of milk. Neither medial nor lateral PBN lesions had any discernible influence on the anorectic action of CCK, however. In combination with the results from a previous study using the same rats (Brain Res. 894 (2001) 288), the present results support the view that the role of the lateral PBN in CCK-induced anorexia depends on the nature of the food used at test.

Effects of peptides on animal and human behavior: a review of studies published in the first twenty years of the journal Peptides

This review catalogs effects of peptides on various aspects of animal and human behavior as published in the journal Peptides in its first twenty years. Topics covered include: activity levels, addiction behavior, ingestive behaviors, learning and memory-based behaviors, nociceptive behaviors, social and sexual behavior, and stereotyped and other behaviors. There are separate tables for these behaviors and a short introduction for each section.

Use of chiral liquid chromatography-tandem mass spectrometry to investigate the metabolism of racemic cholecystokinin-B antagonists

In an attempt to establish the enantiomeric specificity of metabolism for a series of racemic cholecystokinin-B receptor antagonists, chiral LC-MS-MS conditions were established using a Pirkle DNBL chiral stationary phase operating in the reversed-phase mode. Rat liver microsomal incubations of the compounds were analysed using these conditions and it was demonstrated that resolution of oxygenated and demethylated metabolites could be achieved. A single model compound was investigated in detail by obtaining product-ion spectra on all mono-oxygenated species in an attempt to correlate these and identify enantiomeric pairs of metabolites. In this example a lack of differentiation in the product ion spectra did not allow correlation but the results suggest that such an approach may still be viable for the chiral metabolic analysis of racemic material.

Effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides from 1994 through 1998

Effects of peptides on the central nervous system are presented in two ways so as to provide a cross-listing. In the first table, the peptides are listed alphabetically. In the second table, the central nervous system effects are arranged alphabetically. No longer can there be any doubt that peptides affect the central nervous system, sometimes in several ways.

CholecystokininB receptor antagonist increases food intake in rats

To investigate the role of cholecystokininB (CCKB) receptors in the brain in the control of food intake, we administered PD-135158, a specific and potent CCKB antagonist, into the lateral ventricle of male, Sprague-Dawley rats 30 min before a 60-min intake test. PD-135158 (0.001-0.5 mg) increased intake significantly; the mean peak increase was 39% more than the intake after vehicle treatment. The increased intake was due to a larger first meal and more intake during the last 30 min of the test. Because intake during the first 3 min, a measure of palatability or orosensory stimulation did not change significantly, we suggest that antagonism of brain CCK at central CCKB receptors decreased the satiating potency of the ingested food during the meal and decreased the potency of the mechanisms that prevent the reinitiation of eating during the postprandial intermeal interval.