Opiate induced feeding is not dependent on the hippocampus

It has been shown that spreading depression of the hippocampus can elicit feeding, and that several opioid peptides elicit spreading depression when injected into the hippocampus. To determine whether such depression is the primary mechanism by which opiates induce feeding, we tested the feeding effects of naloxone, an opiate antagonist, and butorphanol tartrate, a kappa-sigma agonist, on feeding in rats with and without hippocampal lesions. Naloxone tended to reduce intake approximately equally in the two groups. Similarly, the doses of butorphanol that increased intake in sham rats were equally effective in lesioned rats. It was concluded that the hippocampus is not the major structure mediating opiate-induced feeding.

Peptidergic regulation of feeding in the dog (Canis familiaris)

Although the incidence of obesity in the domesticated dog is high, few studies have investigated the regulation of food intake in this species. In the present study we investigated the response of the dog to a number of putative satiety agents including cholecystokinin (CCK), bombesin, calcitonin and naloxone. CCK significantly suppressed food intake during a scheduled fifteen minute meal in intact dogs and in dogs receiving total subdiaphragmatic vagotomies. Emesis occurred following injection of higher doses of CCK in most dogs. Bombesin and calcitonin reduced intake in both normal and vagotomized dogs, although higher doses of calcitonin were needed to significantly suppress feeding in vagotomized dogs compared with intact animals. Naloxone reduced feeding by as much as 60% in intact and vagotomized animals. Glucagon suppressed feeding in intact dogs, but not in vagotomized animals. Somatostatin and pancreatic polypeptide did not alter food intake. Thus the domesticated dog responds somewhat differently to some neuropeptides compared with the laboratory rat stressing the importance of examining the regulation of food intake across species.

Intraventricular calcitonin gene-related peptide inhibits gastric acid secretion

Calcitonin gene-related peptide (CGRP) is a 37 amino acid peptide recently demonstrated to be a peptide expressed by the calcitonin gene in the rat central nervous system. Intracerebroventricular administration of CGRP in pylorus ligated rats resulted in a dose dependent suppression of gastric acid secretion. This effect was also present in acutely vagotomized rats. In addition, CGRP inhibited the stimulation of gastric acid secretion by thyrotropin releasing hormone. CGRP was considerably less potent in its effect on gastric acid than calcitonin, a well known central inhibitor of gastric acid secretion in the rat. This study suggests that CGRP may be a factor in the central regulation of gastric acid secretion in the rat.

The effects of chronic renal failure and hemodialysis on human red and white cell calmodulin levels

Red blood cell (RBC) and polymorphonuclear white blood cell (WBC) calmodulin levels were measured in 25 uremic patients on regular hemodialysis. Uremic patients had significantly higher RBC [11.45 +/- 0.66 (+/-SE) fg/cell] and WBC (590.5 +/- 110 fg/cell) calmodulin levels than normal subjects (8.62 +/- 0.37 and 130 +/- 30 fg/cell; P less than 0.05). An extremely high RBC calmodulin level (20.58 fg/cell) was found in a patient with sickle cell anemia. Uremic patients on dialysis for 2 yr or more had lower RBC (10.99 +/- 0.58 fg/cell) and WBC (390 +/- 50 fg/cell) calmodulin levels than those who were on dialysis for less than 2 yr (RBC, 12.30 +/- 1.56 fg/cell; WBC, 943 +/- 256 fg/cell; P less than 0.05). There were no statistically significant differences in calmodulin levels when different subgroups of uremic patients were compared, e.g. patients with diabetes mellitus or those receiving supplemental vitamin D, anabolic steroids, or antihypertensive medications. We conclude that calmodulin levels are elevated in uremic patients on regular hemodialysis.

A method for measurement of nanogram quantities of 3-methylcholanthrene in stool samples

The carcinogen 3-methylcholanthrene can be produced from deoxycholic acid and is postulated by some investigators to play a role in the pathogenesis of colon carcinoma. The small quantities of this compound which could be carcinogenic have been difficult to measure in feces because of many potentially interfering compounds. Using 3-[6-14C]methylcholanthrene as an internal standard, petroleum ether extraction, C-18 SepPak separation, preparative high performance liquid chromatography, and gas-liquid chromatography-mass spectrometry with selected ion monitoring, we developed an assay capable of detecting less than 35 ng of 3-methylcholanthrene per gram of stool. Application of this technique to stools of five patients with colon carcinoma and two normal controls revealed no detectable 3-methylcholanthrene in any stool sample. This negative result was confirmed by incubating radiolabeled cholic acid in fecal homogenates. Although greater than 90% of this radiolabeled bile acid was converted to deoxycholic acid, none of the radioactivity was found in the thin-layer chromatography fraction corresponding to 3-methylcholanthrene. These observations provide evidence against a role for 3-methylcholanthrene in pathogenesis of human colon carcinoma. Similar assays could be used for analysis of other carcinogens in stool samples.

Which opioid receptor mechanism modulates feeding?

There is substantial evidence for the role of endogenous opioid peptides in the regulation of appetite. This communication examines the possible opioid peptide mechanism(s) which are involved in appetite regulation. In the rat, activation of both the dynorphin-kappa opioid receptor and the beta-endorphin-epsilon opioid receptor appear to enhance feeding, most probably acting in different areas of the central nervous system. It also appears that rats may have a mu anorectic system. Too few studies have been undertaken to define whether the delta or sigma receptor systems are also involved in feeding responses. It is becoming apparent that a great deal of species diversity exists in the feeding responses to opiates, making it difficult to extrapolate the results obtained in rats to other species. In humans, studies with naloxone suggest an opioid sensitive feeding system which possibly is specifically involved in the regulation of carbohydrate uptake. In addition, we report here preliminary data suggesting the presence of a mu anorectic system in humans. Thus, analogous to the findings for the role of opioid receptors in analgesia, it appears that multiple opioid receptors may be involved in appetite regulation, each receptor relating to a different aspect of feeding.

Zinc deficiency and anorexia in rats: normal feeding patterns and stress induced feeding

We report the effects of zinc deficiency on normal feeding behavior in rats and the effects of zinc deficiency on stress-induced eating in rats. Zinc deficient (ZD) rats weighed significantly less than their pair-fed and ad lib controls. Zinc repletion allowed improved growth, but ZD rats never displayed catch-up growth compared to their ad lib controls. ZD rats rapidly developed a depressed food efficiency ratio which normalized with zinc supplementation. Food consumption in ZD rats was approximately one-third that of ad lib controls and water intake was also significantly reduced. Mild tail pinch was able to induce feeding in these normally anorexic ZD rats. We conclude that zinc deficiency represents an interesting model of anorexia which may enhance our understanding of appetite regulation.

Zinc deficiency and anorexia in rats: the effect of central administration of norepinephrine, muscimol and bromerogocryptine

Anorexia is a major manifestation of zinc deficiency, but the mechanism(s) for this anorexia are not well defined. In this study we investigated the effects of three modulators of feeding response on the food consumption of zinc deficient rats. Zinc deficient rats showed partial resistance to norepinephrine, eating significantly less at the 20 micrograms dose than the zinc sufficient ad lib controls, and food ingestion could not be induced at the 10 micrograms dose. Similarly, higher doses of the GABA agonist, muscimol, were required to induce feeding in the zinc deficient animals compared to the zinc sufficient controls. The dopamine agonist, bromergocryptine, failed to induce feeding in the zinc deficient animals. These findings are compatible with the concept that zinc deficiency produces a generalized decrease in receptor responsibility, possibly secondary to alterations in membrane fluidity.

The role of the endogenous opiates in zinc deficiency anorexia

Anorexia is a major symptom of zinc deficiency, but the mechanism(s) for this anorexia are poorly defined. Recent studies have suggested an integral role for endogenous opiate peptides in appetite regulation. Dynorphin, a leucine-enkephalin containing opiate peptide, is a potent inducer of spontaneous feeding. In this study we showed that zinc deficient animals were relatively resistant to dynorphin-induced feeding. Measurement of dynorphin levels using a highly sensitive radioimmunoassay showed that zinc deficient animals had lower levels of dynorphin in the hypothalamus than did ad lib fed animals, with weight restricted animals having intermediate values. [3H]-naloxone binding was significantly increased to isolated brain membranes from zinc deficient animals using 1 nM unlabeled naloxone when compared to ad lib fed controls with the weight restricted animals again having intermediate values. These data suggest that abnormalities in endogenous opiate regulation of appetite may well play a role in the anorexia of zinc deficiency. The effects of zinc deficiency on endogenous opiate action appear to include alterations in receptor affinity, a post-receptor defect and alterations in the synthesis and/or release of dynorphin.

Effects of cigarette smoke and nicotine on feeding and energy

Much evidence has accumulated indicating that cigarette smokers weigh less than non-smokers and that smokers gain weight when they cease smoking. In the present study we evaluated the effects of cigarette smoke and nicotine on food intake, weight gain, resting energy output, brown fat mass and opiate binding (opiates initiate feeding in sated rats) in rats. Chronic smoke exposure slightly suppressed growth rate and food intake after 14 days of smoke exposure. Blood glucose levels and intrascapular brown adipose mase were increased as a result of smoke exposure. Hamsters chronically exposed to cigarette smoke decreased body weight; however, food intake was not significantly suppressed. Short term (5 day) exposure to nicotine (4 and 2 mg/kg/day) suppressed growth rate and food intake. Nicotine (4 and 2 mg/kg) significantly suppressed water ingestion in water-deprived rats and altered the quantities of flavored solutions ingested by rats compared with those ingested by rats receiving no nicotine. Thus cigarette smoke and nicotine exposure affects food intake, energy utilization and taste perception; all parameters which contribute to overall body mass; however, these parameters change in a complex manner with only small changes occurring at specific time intervals.

Variations in aryl hydrocarbon hydroxylase activities in mitogen-activated human and nonhuman primate lymphocytes

A fluorometric assay for the cytochrome P-450-dependent enzyme system, aryl hydrocarbon hydroxylase (AHH), was performed in mitogen-activated human lymphocytes from over 300 different humans and from 64 baboons. Results reveal: a) an average interindividual variation in AHH activity of approximately 0.25 (coefficient of variation); range of activities among humans and baboon subjects of approximately 40-fold; c) both genetic and environmental determinants of interindividual variation, and d) high AHH activity in humans associated with primary lung cancer. Confirmation of these results awaits the development of improved methods for phenotyping humans and for prospective cancer patient studies. DNA probes might be employed in future studies to determine specific mRNA content, and to search for DNA polymorphisms in and near the human cytochrome P-450 gene.

The effects of aging and diabetes mellitus on human red and white cell calmodulin levels (chemotaxis/phagocytosis/calcium)

Both the calcium ion and calmodulin have been proposed to play a role in producing the intracellular effects of insulin. Abnormalities in calmodulin levels have previously been reported in tissues from diabetic animals. Thus, using a sensitive and specific radioimmunoassay, we measured calmodulin levels in red cells and polymorphonuclear leukocytes from humans with diabetes mellitus. Diabetic patients have significantly lower white cell calmodulin levels than age-matched controls. There were no significant differences in red cell calmodulin levels in diabetics compared with controls. Red cell calmodulin levels in normal subjects were decreased with advancing age. We conclude that the alteration in calmodulin levels in leukocytes from diabetics may be associated with the decreased neutrophil function that has been observed in diabetics.

Aryl hydrocarbon hydroxylase inducibility among primary relatives of children with leukemia or solid tumors

In mice, there is a correlation between genetically regulated levels of inducible aryl hydrocarbon hydroxylase (AHH) activity and the risk of polycyclic hydrocarbon-induced leukemia or solid tumors. Recent clinical studies suggest a relationship between high AHH activity and lung cancer associated with cigarette smoking (Kouri, R.E., McKinney, C.E., Slomiany, D.J., Snodgrass, D.R., Wray, N.P., and McLemore, T.L. Cancer Res. 42: 5030-5037, 1982). To determine whether there is a similar genetic relationship in humans between inducible AHH and the occurrence of pediatric cancers, we examined AHH activity in mitogen-stimulated benzo(a)anthracene-treated lymphocyte cultures from primary relatives of children with leukemia or solid tumors. Control families (parents and siblings with no history of cancer) comprised friends or neighbors of the proband families. By comparing variance among family members with variance among nonrelated individuals, we conclude that a small, but real, genetic component is detectable. Adjusting for age, smoking history, and the length of time during which the lymphocytes had been cryopreserved, however, we find no difference among 77 leukemia, 71 solid tumor, and 100 control family members with regard to median units (+/- median S.E.) of maximally induced AHH activity per unit of reduced nicotinamide adenine dinucleotide-cytochrome c reductase activity: 0.31 +/- 0.03; 0.28 +/- 0.03; and 0.28 +/- 0.03, respectively. Thus, benzo(a)anthracene-induced AHH activity in cultured mitogen-activated lymphocytes in our study population does not appear to be associated with the risk of occurrence of childhood leukemia or solid tumors.

Thermoregulatory effects of purines and caffeine

Purines are putative neurotransmitters which appear to be involved in regulating several vegetative functions. We examined the effect of purines and their antagonist, caffeine, on colonic temperature of rats. Adenosine injected ip lowered colonic temperature in a dose responsive manner at ambient room temperatures. Adenine and AMP also lowered body temperature whereas 7-methylinosine and inosine only slightly influenced colonic temperature. Caffeine (50 mg/kg) injected sc, increased colonic temperature and when injected within 60 seconds of adenosine, counteracted the hypothermic effect of adenosine (50 mg/kg). Low ambient temperature (4 degrees C) accentuated the thermoregulatory effects of adenosine. Thus adenosine appears to have a hypothermic effect on body temperature regulation when administered peripherally which can be reversed by caffeine.

Are peptides truly satiety agents? A method of testing for neurohumoral satiety effects

Because controversy exists as to the interpretation of the known feeding-suppressive effects of various neuropeptides, we attempted to construct a model that could differentiate satiety from other nonspecific effects. Reasoning that a satiety factor should be less inhibiting of feeding in a hungrier animal, whereas aversive agents should be unaffected by hunger, we studied the neuropharmacologic dose responses of five substances administered peripherally to rats at two different degrees of starvation. Included were four neuropeptides with putative satiety effects: cholecystokinin, calcitonin, bombesin, and pancreatic polypeptide, as well as the known aversive agent lithium chloride. In the study, cholecystokinin behaved as we postulated a satiety factor would, showing significant effect of starvation at every dose and in the ANOVA. The aversive agent lithium showed overlapping among the starvation groups and no starvation effect by ANOVA. Calcitonin failed to show differences attributable to starvation. Bombesin produced some overlapping of starvation groups and a barely significant starvation effect by ANOVA. Pancreatic polypeptide produced no feeding suppression in the rat. We conclude that cholecystokinin is a short-term satiety signal and that calcitonin acts peripherally by some nonspecific nonsatiating means. Bombesin's effects are unclear but may be nonspecific.

Adrenal modulation of the inhibitory effect of corticotropin releasing factor on feeding

Corticotropin releasing factor (CRF) reduces food intake in rats after central administration. In these studies we examined whether the adrenal gland and the vagus were involved in CRF suppression of intake. One hour intake was reduced by a 5 micrograms (ICV) injection of CRF in sham but not adrenalectomized rats maintained on 0.9% NaCl. In a separate experiment on rats maintained on tap water, the inhibitory effect of CRF (5 micrograms) lasted at least 4 hours in sham rats whereas adrenalectomized rats did not significantly differ from controls. These experiments suggest that the adrenal gland modulates the feeding response to CRF. As replacement with corticosterone (0.75 mg/kg) in total adrenalectomized rats did not restore responsiveness to 5 or 10 micrograms of CRF, we next studied whether the adrenal medulla was responsible for the decreased responsiveness to CRF. In rats lacking the adrenal medulla only, food intake was reduced by a 5 microgram injection of CRF; in sham rats, intake was significantly reduced by doses as low as 0.1 microgram of CRF. An additional experiment examined the effect of gastric vagotomy on the CRF feeding response. Vagotomized rats were as responsive to 5 and 10 microgram injections of CRF as sham rats, which suggests that the effect is not dependent on the vagus nerve. These findings indicate that the adrenal gland, primarily the medulla, plays an intermediate role in the reduction of food intake caused by central injections of CRF. This conclusion is consistent with the known effect of CRF on adrenomedullary discharge.

A comparison of the effects of corticotropin releasing factor and sauvagine on food intake

Corticotropin releasing factor (CRF) and sauvagine (SVG) when administered ICV both reduced spontaneous feeding as well as feeding induced by deprivation or the administration of ethylketocyclazocine (EKC). For spontaneous- and EKC-induced feeding, SVG produced a larger and longer-lasting suppressive effect than did CRF. Both peptides produced a conditioned taste aversion when paired with a novel saccharin taste. As the feeding effects, SVG produced a stronger aversion than CRF. These studies further establish the similarity between CRF and SVG and suggest that they may have a disruptive effect on feeding.

N-allylnormetazocine (SKF-10,047): the induction of feeding by a putative sigma agonist

Several distinct classes of opiate receptors have been postulated. It has been suggested that two of these, the kappa and sigma, may play a role in the initiation of feeding. The putative sigma receptor agonist N-allylnormetazocine increased food intake at doses of 0.1 and 1 mg/kg, whereas higher doses caused a decreased intake under some conditions. This stimulatory effect increased after repeated injections and was naloxone reversible. After repeated injections of N-allylnormetazocine, the feeding response to ketocyclazocine, but not morphine, appeared at an earlier point than in naive rats. These experiments support the suggestion that the sigma receptor may play some role in the initiation of feeding.

The kappa opioid receptor, ingestive behaviors and the obese mouse (ob/ob)

Recent studies have suggested a role for the kappa opiate receptor and its endogenous ligand, dynorphin, in the central regulation of appetite. In this study we found that the ob/ob mouse was mildly resistant to the ability of three kappa agonists, viz, butorphanol, tifluadom, and ketocyclazocine to induce food intake. In addition, we could find no change in ir-dynorphin levels in 7 areas for the central nervous system. These findings do not provide evidence for a role of kappa opioid feeding system in the pathogenesis of obesity in the ob/ob mouse.

Involvement of dynorphin and the kappa opioid receptor in feeding

Dynorphin-(1-17) produces a highly specific increase in food ingestion. Similar enhancement of food ingestion is found with dynorphin fragments (1-10), (1-11), (1-13) and (3-13) but not with (1-8) and (1-9). Dynorphin B (rimorphin) also enhances food intake. The highly specific kappa agonist U-50,488 also enhances food intake as do a number of other kappa-opiate receptor agonists. These studies provided further for the role of a highly specific dynorphin-kappa opioid receptor in the modulation of feeding.

Adenovirus 2 early gene expression promotes susceptibility to effector cell lysis of hybrids formed between hamster cells transformed by adenovirus 2 and simian virus 40

Weakly oncogenic adenovirus 2 (Ad2)-transformed LSH hamster cells are sensitive to lysis by spontaneously cytolytic lymphoid cells and activated macrophages, whereas highly oncogenic simian virus 40 (SV40)-transformed LSH cells are relatively resistant to these nonspecific effector cells. Somatic cell hybrids formed between Ad2- and SV40-transformed hamster cells, which expressed Ad2 tumor (T) antigens, exhibited an increased cytolytic susceptibility compared to Ad2 T antigen-negative cell hybrids or nonhybrid SV40-transformed cells. No correlation was found between the expression of SV40 T antigen in hybrid cells and cytolytic susceptibility. The results suggest the existence of a novel function for early Ad2 genome-encoded polypeptides (T antigens) expressed in transformed hamster cells--the induction of susceptibility to destruction mediated by immunologically nonspecific effector cells.