Factors regulating vagal sensory development: potential role in obesities of developmental origin

Changes in gut-brain axis parameters in adult rats of both sexes with different feeding pattern that were early nicotine-exposed

Nicotine is an endocrine disruptor and imprinting factor during breastfeeding that can cause food intake imbalance in the adulthood. As nicotine affects the intestinal microbiota, altering the composition of the bacterial communities and short-chain fatty acids (SCFAs) synthesis in a sex-dependent manner, we hypothesized that nicotine could program the gut-brain axis, consequently modifying the eating pattern of adult male and female rats in a model of maternal nicotine exposure (MNE) during breastfeeding. Lactating Wistar rat dams received minipumps that release 6 mg/kg/day of nicotine (MNE group) or saline for 14 days. The progeny received standard diet from weaning until euthanasia (26 weeks of age). We measured: in vivo electrical activity of the vagus nerve; c-Fos expression in the nucleus tractus solitarius, gastrointestinal peptides receptors, intestinal brain-derived neurotrophic factor (BDNF), SCFAs and microbiota. MNE females showed hyperphagia despite normal adiposity, while MNE males had unchanged food intake, despite obesity. Adult MNE offspring showed decreased Bacteroidetes and increased Firmicutes, Actinobacteria and Proteobacteria. MNE females had lower fecal acetate while MNE males showed higher vagus nerve activity. In summary nicotine exposure through the milk induces long-term intestinal dysbiosis, which may affect eating patterns of adult offspring in a sex-dependent manner.

Upregulation of proBDNF in the Mesenteric Lymph Nodes in Septic Mice

The immune status in the lymphatic system, especially mesenteric lymph nodes (MLNs), is critical to regulate the septic shock. Brain-derived neurotrophic factor (BDNF) in the enteric system has been reported to regulate enteric immunity. However, the role of its precursor, proBDNF, in the immune status of MLNs under sepsis condition is still unclear. This study aimed to characterize the expression pattern of proBDNF in MLNs after lipopolysaccharide (LPS) stimulation, and to investigate the association of pathogenesis of sepsis. LPS (20 mg/kg) was intraperitoneally injected to induce sepsis in mice. Survival curve analysis, routine blood tests, and liver and kidney function tests were performed to evaluate the severity of sepsis. QPCR and histological staining were performed to assess the mRNA levels of proinflammatory cytokines and degree of immune-inflammatory response in the MLNs. Furthermore, Western blotting, flow cytometry, and immunofluorescence were performed to examine the key molecules expression of proBDNF signaling. Intraperitoneal LPS injection significantly decreased the number of lymphocytes in blood but increased the number of T lymphocytes in MLNs. Serum alanine transaminase, aspartate transaminase, and blood urea nitrogen levels were increased in LPS-challenged mice compared to control mice. LPS administration upregulated proinflammatory cytokine gene expression and induced histological changes in the MLNs. LPS injection increased BDNF, proBDNF, and its receptor pan neutrophin receptor 75 (p75^NTR) expression in MLNs. The increased proBDNF was mainly localized on CD3⁺ and CD4⁺ T cells in the medulla of MLNs. LPS-induced sepsis upregulated proBDNF expression in medulla T cells of MLNs. ProBDNF upregulation may be involved in the pathogenesis of septic shock.

Up-regulation of transient receptor potential vanilloid (TRPV) and down-regulation of brain-derived neurotrophic factor (BDNF) expression in patients with functional dyspepsia (FD)

BACKGROUND

The role of immune activation in Functional Dyspepsia (FD) patients without previous infection is unclear. We compare the gastric and circulating brain-derived neurotropic factor (BDNF), receptor potential vanilloid type (TRPV) families and various cytokines in FD patients.

METHODS

Consecutive adult FD patients (Rome III) with no recent history of gastroenteritis and asymptomatic healthy controls were recruited for upper endoscopy. Subjects with GERD and IBS as predominant symptoms, diabetes mellitus, current or previous Helicobacter pylori infection, psychiatric illness and recent use of NSAID or PPI were excluded. Corpus biopsies and serum samples were collected.

KEY RESULTS

Forty three [M:F=8:35, mean age: 35.0 (9.3)] FD patients were compared with 23 healthy controls [M:F=8:15, mean age: 36.6 (10.2)]. FD patients had postprandial distress syndrome (PDS) as predominant sub-type (PDS: 36, EPS: 2). There was no significant difference in the median inflammation score (FD:0 (0-1) vs Control:0 (0-1), P=.79). However, FD patients had significantly higher mRNA expression of TRPV1 (FD:0.014±0.007, Control:0.003±0.001, 4.6 fold, P=.02) and TRPV2 (FD:0.012±0.006, Control:0.003±0.001, 4 fold, P=.02) compared to controls. The serum (FD:258.0±12.3 ng ml^-1 , Control:319.7±18.1 ng ml^-1 , P<.01) and gastric BDNF mRNA (FD:0.06±0.008, Control:0.092±0.01, 0.65 fold, P=.02)levels significantly lower in FD patients. Secretion of cytokines (IL-4, IL-5, IL-6, IL-8, IL-10, G-CSF, TGF-β2, MCP-1)was also highly correlated with dyspeptic symptoms in patients with FD.

CONCLUSIONS & INFERENCES

Despite lacking gastric mucosal inflammation, up-regulation of TRPV1 and TRPV2, down-regulation of BDNF were observed in FD patients. These suggest that immune alteration may contribute to the pathogenesis of FD without any previous infection.

Development of the intrinsic and extrinsic innervation of the gut

The gastrointestinal (GI) tract is innervated by intrinsic enteric neurons and by extrinsic efferent and afferent nerves. The enteric (intrinsic) nervous system (ENS) in most regions of the gut consists of two main ganglionated layers; myenteric and submucosal ganglia, containing numerous types of enteric neurons and glial cells. Axons arising from the ENS and from extrinsic neurons innervate most layers of the gut wall and regulate many gut functions. The majority of ENS cells are derived from vagal neural crest cells (NCCs), which proliferate, colonize the entire gut, and first populate the myenteric region. After gut colonization by vagal NCCs, the extrinsic nerve fibers reach the GI tract, and Schwann cell precursors (SCPs) enter the gut along the extrinsic nerves. Furthermore, a subpopulation of cells in myenteric ganglia undergoes a radial (inward) migration to form the submucosal plexus, and the intrinsic and extrinsic innervation to the mucosal region develops. Here, we focus on recent progress in understanding the developmental processes that occur after the gut is colonized by vagal ENS precursors, and provide an up-to-date overview of molecular mechanisms regulating the development of the intrinsic and extrinsic innervation of the GI tract.

Stimulation of synthesis and release of brain-derived neurotropic factor from intestinal smooth muscle cells by substance P and pituitary adenylate cyclase-activating peptide

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a neurotrophin present in the intestine where it participates in survival and growth of enteric neurons, augmentation of enteric circuits, and stimulation of intestinal peristalsis and propulsion. Previous studies largely focused on the role of neural and mucosal BDNF. The expression and release of BDNF from intestinal smooth muscle and the interaction with enteric neuropeptides has not been studied in gut.

METHODS

The expression and secretion of BDNF from smooth muscle cultured from the rabbit intestinal longitudinal muscle layer in response to substance P (SP) and pituitary adenylate cyclase-activating peptide (PACAP) was measured by western blot and enzyme-linked immunosorbent assay. BDNF mRNA was measured by reverse-transcription polymerase chain reaction.

KEY RESULTS

The expression of BNDF protein and mRNA was greater in smooth muscle cells (SMCs) from the longitudinal muscle than from circular muscle layer. PACAP and SP increased the expression of BDNF protein and mRNA in cultured longitudinal SMCs. PACAP and SP also stimulated the secretion of BDNF from cultured longitudinal SMCs. Chelation of intracellular calcium with BAPTA (1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) prevented SP-induced increase in BDNF mRNA and protein expression and SP-induced secretion of BDNF.

CONCLUSIONS & INFERENCES

Neuropeptides known to be present in enteric neurons innervating the longitudinal layer increase the expression of BDNF mRNA and protein in SMCs and stimulate the release of BDNF. Considering the ability of BDNF to enhance smooth muscle contraction, this autocrine loop may partially explain the characteristic hypercontractility of longitudinal muscle in inflammatory bowel disease.

Exposure to a high fat diet during the perinatal period alters vagal motoneurone excitability, even in the absence of obesity

KEY POINTS

Obesity is recognized as being multifactorial in origin, involving both genetic and environmental factors. The perinatal period is known to be critically important in the development of neural circuits responsible for energy homeostasis and the integration of autonomic reflexes. Diet-induced obesity alters the biophysical, pharmacological and morphological properties of vagal neurocircuits regulating upper gastrointestinal tract functions, including satiety. Less information is available, however, regarding the effects of a high fat diet (HFD) itself on the properties of vagal neurocircuits. The present study was designed to test the hypothesis that exposure to a HFD during the perinatal period alters the electrophysiological, pharmacological and morphological properties of vagal efferent motoneurones innervating the stomach. Our data indicate that perinatal HFD decreases the excitability of gastric-projecting dorsal motor nucleus neurones and dysregulates neurotransmitter release from synaptic inputs and that these alterations occur prior to the development of obesity. These findings represent the first direct evidence that exposure to a HFD modulates the processing of central vagal neurocircuits even in the absence of obesity. The perinatal period is critically important to the development of autonomic neural circuits responsible for energy homeostasis. Vagal neurocircuits are vital to the regulation of upper gastrointestinal functions, including satiety. Diet-induced obesity modulates the excitability and responsiveness of both peripheral vagal afferents and central vagal efferents but less information is available regarding the effects of diet per se on vagal neurocircuit functions. The aims of this study were to investigate whether perinatal exposure to a high fat diet (HFD) dysregulated dorsal motor nucleus of the vagus (DMV) neurones, prior to the development of obesity. Whole cell patch clamp recordings were made from gastric-projecting DMV neurones in thin brainstem slices from rats that were exposed to either a control diet or HFD from pregnancy day 13. Our data demonstrate that following perinatal HFD: (i) DMV neurones had decreased excitability and input resistance with a reduced ability to fire action potentials; (ii) the proportion of DMV neurones excited by cholecystokinin (CCK) was unaltered but the proportion of neurones in which CCK increased excitatory glutamatergic synaptic inputs was reduced; (iii) the tonic activation of presynaptic group II metabotropic glutamate receptors on inhibitory nerve terminals was attenuated, allowing modulation of GABAergic synaptic transmission; and (iv) the size and dendritic arborization of gastric-projecting DMV neurones was increased. These results suggest that perinatal HFD exposure compromises the excitability and responsiveness of gastric-projecting DMV neurones, even in the absence of obesity, suggesting that attenuation of vago-vagal reflex signalling may precede the development of obesity.

Reduced intestinal brain-derived neurotrophic factor increases vagal sensory innervation of the intestine and enhances satiation

Brain-derived neurotrophic factor (BDNF) is produced by developing and mature gastrointestinal (GI) tissues that are heavily innervated by autonomic neurons and may therefore control their development or function. To begin investigating this hypothesis, we compared the morphology, distribution, and density of intraganglionic laminar endings (IGLEs), the predominant vagal GI afferent, in mice with reduced intestinal BDNF (INT-BDNF(-/-)) and controls. Contrary to expectations of reduced development, IGLE density and longitudinal axon bundle number in the intestine of INT-BDNF(-/-) mice were increased, but stomach IGLEs were normal. INT-BDNF(-/-) mice also exhibited increased vagal sensory neuron numbers, suggesting that their survival was enhanced. To determine whether increased intestinal IGLE density or other changes to gut innervation in INT-BDNF(-/-) mice altered feeding behavior, meal pattern and microstructural analyses were performed. INT-BDNF(-/-) mice ate meals of much shorter duration than controls, resulting in reduced meal size. Increased suppression of feeding in INT-BDNF(-/-) mice during the late phase of a scheduled meal suggested that increased satiation signaling contributed to reduced meal duration and size. Furthermore, INT-BDNF(-/-) mice demonstrated increases in total daily intermeal interval and satiety ratio, suggesting that satiety signaling was augmented. Compensatory responses maintained normal daily food intake and body weight in INT-BDNF(-/-) mice. These findings suggest a target organ-derived neurotrophin suppresses development of that organ's sensory innervation and sensory neuron survival and demonstrate a role for BDNF produced by peripheral tissues in short-term controls of feeding, likely through its regulation of development or function of gut innervation, possibly including augmented intestinal IGLE innervation.

Brain-derived neurotrophic factor enhances cholinergic contraction of longitudinal muscle of rabbit intestine via activation of phospholipase C

Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family of proteins best known for its role in neuronal survival, differentiation, migration, and synaptic plasticity in central and peripheral neurons. BDNF is also widely expressed in nonneuronal tissues including the gastrointestinal tract. The role of BDNF in intestinal smooth muscle contractility is not well defined. The aim of this study was to identify the role of BDNF in carbachol (CCh)- and substance P (SP)-induced contraction of intestinal longitudinal smooth muscle. BDNF, selective tropomyosin-related kinase B (TrkB) receptor agonists, and pharmacological inhibitors of signaling pathways were examined for their effects on contraction of rabbit intestinal longitudinal muscle strips induced by CCh and SP. BDNF activation of intracellular signaling pathways was examined by Western blot in homogenates of muscle strips and isolated muscle cells. One-hour preincubation with BDNF enhanced intestinal muscle contraction induced by CCh but not by SP. The selective synthetic TrkB agonists LM 22A4 and 7,8-dihydroxyflavone produced similar effects to BDNF. The Trk antagonist K-252a, a TrkB antibody but not p75NTR antibody, blocked the effect of BDNF. The enhancement of CCh-induced contraction by BDNF was blocked by the phospholipase C (PLC) antagonist U73122, but not by ERK1/2 or Akt antagonists. Direct measurement in muscle strips and isolated muscle cells showed that BDNF caused phosphorylation of TrkB receptors and PLC-γ, but not ERK1/2 or Akt. We conclude that exogenous BDNF augments the CCh-induced contraction of longitudinal muscle from rabbit intestine by activating TrkB receptors and subsequent PLC activation.

Mechanism of hyperphagia contributing to obesity in brain-derived neurotrophic factor knockout mice

Global-heterozygous and brain-specific homozygous knockouts (KOs) of brain-derived neurotrophic factor (BDNF) cause late- and early-onset obesity, respectively, both involving hyperphagia. Little is known about the mechanism underlying this hyperphagia or whether BDNF loss from peripheral tissues could contribute to overeating. Since global-homozygous BDNF-KO is perinatal lethal, a BDNF-KO that spared sufficient brainstem BDNF to support normal health was utilized to begin to address these issues. Meal pattern and microstructure analyses suggested overeating of BDNF-KO mice was mediated by deficits in both satiation and satiety that resulted in increased meal size and frequency and implicated a reduction of vagal signaling from the gut to the brain. Meal-induced c-Fos activation in the nucleus of the solitary tract, a more direct measure of vagal afferent signaling, however, was not decreased in BDNF-KO mice, and thus was not consistent with a vagal afferent role. Interestingly though, meal-induced c-Fos activation was increased in the dorsal motor nucleus of the vagus nerve (DMV) of BDNF-KO mice. This could imply that augmentation of vago-vagal digestive reflexes occurred (e.g., accommodation), which would support increased meal size and possibly increased meal number by reducing the increase in intragastric pressure produced by a given amount of ingesta. Additionally, vagal sensory neuron number in BDNF-KO mice was altered in a manner consistent with the increased meal-induced activation of the DMV. These results suggest reduced BDNF causes satiety and satiation deficits that support hyperphagia, possibly involving augmentation of vago-vagal reflexes mediated by central pathways or vagal afferents regulated by BDNF levels.

Vagal afferent controls of feeding: a possible role for gastrointestinal BDNF

INTRODUCTION

Vagal gastrointestinal (GI) afferents do not appear to contribute to long-term controls of feeding, despite downstream connections that could support such a role. This view is largely attributable to a lack of evidence for long-term effects, especially the failure of vagal afferent lesions to produce hyperphagia or obesity.

AIMS

Here, the possibility is evaluated that "side effects" of vagal lesion methods resulting largely from complexities of vagal organization would probably suppress long-term effects. Criteria based on knowledge of vagal organization were utilized to critique and compare vagal lesion methods and to interpret their effects on GI function, feeding and body weight.

RESULTS AND CONCLUSIONS

This analysis suggested that it was premature to eliminate a long-term vagal GI afferent role based on the effects of these lesions and highlighted aspects of vagal organization that must be addressed to reduce the problematic side effects of vagal lesions. The potential of "genetic" lesions that alter vagal sensory development to address these aspects, examination of the feasibility of this approach, and the properties of brain-derived neurotrophic factor (BDNF) that made it an attractive candidate for application of this approach are described. BDNF knockout from GI smooth muscle unexpectedly demonstrated substantial overeating and weight gain associated with increased meal size and frequency. The decay of eating rate during a scheduled meal was also reduced. However, meal-induced c-Fos activation was increased in the dorsal motor nucleus of the vagus, suggesting that the effect on eating rate was due to augmentation of GI reflexes by vagal afferents or other neural systems.

Early postnatal overnutrition: potential roles of gastrointestinal vagal afferents and brain-derived neurotrophic factor

Abnormal perinatal nutrition (APN) results in a predisposition to develop obesity and the metabolic syndrome and thus may contribute to the prevalence of these disorders. Obesity, including that which develops in organisms exposed to APN, has been associated with increased meal size. Vagal afferents of the gastrointestinal (GI) tract contribute to regulation of meal size by transmitting satiation signals from gut-to-brain. Consequently, APN could increase meal size by altering this signaling, possibly through changes in expression of factors that control vagal afferent development or function. Here two studies that addressed these possibilities are reviewed. First, meal patterns, meal microstructure, and the structure and density of vagal afferents that innervate the intestine were examined in mice that experienced early postnatal overnutrition (EPO). These studies provided little evidence for EPO effects on vagal afferents as it did not alter meal size or vagal afferent density or structure. However, these mice exhibited modest hyperphagia due to a satiety deficit. In parallel, the possibility that brain-derived neurotrophic factor (BDNF) could mediate APN effects on vagal afferent development was investigated. Brain-derived neurotrophic factor was a strong candidate because APN alters BDNF levels in some tissues and BDNF knockout disrupts development of vagal sensory innervation of the GI tract. Surprisingly, smooth muscle-specific BDNF knockout resulted in early-onset obesity and hyperphagia due to increases in meal size and frequency. Microstructure analysis revealed decreased decay of intake rate during a meal in knockouts, suggesting that the loss of vagal negative feedback contributed to their increase in meal size. However, meal-induced c-Fos activation within the dorsal vagal complex suggested this effect could be due to augmentation of vago-vagal reflexes. A model is proposed to explain how high-fat diet consumption produces increased obesity in organisms exposed to APN, and may be required to reveal effects of EPO on vagal function.

Development of the vagal innervation of the gut: steering the wandering nerve

BACKGROUND

The vagus nerve is the major neural connection between the gastrointestinal tract and the central nervous system. During fetal development, axons from the cell bodies of the nodose ganglia and the dorsal motor nucleus grow into the gut to find their enteric targets, providing the vagal sensory and motor innervations respectively. Vagal sensory and motor axons innervate selective targets, suggesting a role for guidance cues in the establishment of the normal pattern of enteric vagal innervation.

PURPOSE

This review explores known molecular mechanisms that guide vagal innervation in the gastrointestinal tract. Guidance and growth factors, such as netrin-1 and its receptor, deleted in colorectal cancer, extracellular matrix molecules, such as laminin-111, and members of the neurotrophin family of molecules, such as brain-derived neurotrophic factor have been identified as mediating the guidance of vagal axons to the fetal mouse gut. In addition to increasing our understanding of the development of enteric innervation, studies of vagal development may also reveal clinically relevant insights into the underlying mechanisms of vago-vagal communication with the gastrointestinal tract.

Molecular development of the extrinsic sensory innervation of the gastrointestinal tract

The extrinsic sensory innervation of the gastrointestinal tract is the conduit through which the gut and the central nervous system communicate. The hindbrain receives information directly from the bowel via the vagus nerve, while information from spinal afferents arrives in the central nervous system through the dorsal root ganglia. This review focuses on the molecular development of these vagal and spinal innervations, with an emphasis on mechanisms that involve axon guidance. During development, axons from both the nodose ganglia and dorsal root ganglia grow into the gut, innervate their appropriate enteric targets and avoid inappropriate cells in the gut wall. These developmental outcomes suggest that both attractive and repellent molecules are important in establishing the normal pattern of the extrinsic sensory innervation. In the fetal mouse gut, the guidance of vagal sensory axons is mediated by axon guidance molecules, such as netrin and the netrin receptor, deleted in colorectal cancer (DCC), as well as extracellular matrix molecules, such as laminin-111. Dorsal root ganglion neurons are known to express, and their axons to respond to, axon guidance molecules. The question of whether or not these molecules are involved in guiding spinal afferents to the bowel, however, has not yet been examined. It is anticipated that a better understanding of how vagal and spinal afferents innervate the fetal gut and reach specific enteric locations will provide deeper insights into the underlying mechanisms of normal and abnormal sensation from the gastrointestinal tract.

Mice deficient in brain-derived neurotrophic factor have altered development of gastric vagal sensory innervation

Vagal sensory neurons are dependent on neurotrophins for survival during development. Here, the contribution of brain-derived neurotrophic factor (BDNF) to survival and other aspects of gastric vagal afferent development was investigated. Post-mortem anterograde tracing with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbo-cyanine perchlorate (DiI) was used to label selectively vagal projections to the stomach on postnatal days (P) 0, 3, 4, and 6 in wild types and heterozygous or homozygous BDNF mutants. Sampling sites distributed throughout the ventral stomach wall were scanned with a confocal microscope, and vagal axon bundles, single axons, putative mechanoreceptor precursors (intraganglionic laminar endings, IGLEs; intramuscular arrays, IMAs), and efferent terminals were quantified. Also, myenteric neurons, which are innervated by IGLEs, were stained with cuprolinic blue and counted. Quantitative comparisons across wild-type stomach compartments demonstrated that the adult distribution of IMAs was not present at P0 but began to form by P3-6. Among all the quantified elements, at P0, only IGLE density was significantly different in homozygous mutants compared with wild types, exhibiting a 50% reduction. Also, antrum innervation appeared disorganized, and some putative IMA precursors had truncated telodendria. At P3-6, the effect on IGLEs had recovered, the disorganization of antrum innervation had partially recovered, and some IMA telodendria were still truncated. The present results suggest that gastric IGLEs are among the vagal sensory neurons dependent on BDNF for survival or axon guidance. Alternatively, BDNF deficiency may delay gastric IGLE development. Also, BDNF may contribute to IMA differentiation and patterning of antral vagal innervation.

Meal parameters and vagal gastrointestinal afferents in mice that experienced early postnatal overnutrition

Early postnatal overnutrition results in a predisposition to develop obesity due in part to hypothalamic and sympathetic dysfunction. Potential involvement of another major regulatory system component--the vagus nerve--has not been examined. Moreover, feeding disturbances have rarely been investigated prior to development of obesity when confounds due to obesity are minimized. To examine these issues, litters were culled on the day of birth to create small litters (SL; overnutrition), or normal size litters (NL; normal nutrition). Body weight, fat pad weight, meal patterns, and vagal sensory duodenal innervation were compared between SL and NL adult mice prior to development of obesity. Meal patterns were studied 18 h/day for 3 weeks using a balanced diet. Then vagal mechanoreceptors were labeled using anterograde transport of wheatgerm agglutinin-horseradish peroxidase injected into the nodose ganglion and their density and morphology were examined. Between postnatal day 1 and weaning, body weight of SL mice was greater than for NL mice. By young adulthood it was similar in both groups, whereas SL fat pad weight was greater in males, suggesting postnatal overnutrition produced a predisposition to obesity. SL mice exhibited increased food intake, decreased satiety ratio, and increased first meal rate (following mild food deprivation) compared to NL mice, suggesting postnatal overnutrition disrupted satiety. The density and structure of intestinal IGLEs appeared similar in SL and NL mice. Thus, although a vagal role cannot be excluded, our meal parameter and anatomical findings provided no evidence for significant postnatal overnutrition effects on vagal gastrointestinal afferents.

Alimentary Epigenetics: A Developmental Psychobiological Systems View of the Perception of Hunger, Thirst and Satiety

Hunger, thirst and satiety have an enormous influence on cognition, behavior and development, yet we often take for granted that they are simply inborn or innate. Converging data and theory from both comparative and human domains, however, supports the conclusion that the phenomena hunger, thirst and satiety are not innate but rather emerge probabilistically as a function of experience during individual development. The metatheoretical perspective provided by developmental psychobiological systems theory provides a useful framework for organizing and synthesizing findings related to the development of the perception of hunger, thirst and satiety, or alimentary interoception. It is argued that neither developmental psychology nor the psychology of eating and drinking have adequately dealt with the ontogeny of alimentary interoception and that a more serious consideration of the species-typical developmental system of food and fluid intake and the many modifications that have been made therein is likely necessary for a full understanding of both alimentary and emotional development.