Effects of intracerebroventricular injection of dynorphin, leumorphin and alpha neo-endorphin on operant feeding in pigs

Young pigs, which are useful experimental animals for biomedical research, were prepared with lateral intracerebroventricular (ICV) cannulae and housed individually in cages fitted with operant panels, with food and water ad lib. ICV injection of 200 micrograms of dynorphin A 1-17 or 1-13 resulted in a significant meal commencing within 2-5 min. Shorter fragments of dynorphin (1-10, 1-9, 1-8) were ineffective at inducing feeding as was dynorphin B (rimorphin). In the same situation, leumorphin and alpha neo-endorphin (200 micrograms) elicited significant feeding but beta neo-endorphin did not. Dynorphin 1-17 or 1-13, administered 5 min before feeding started, increased meal size when pigs were fed after 4-h deprivation. Naloxone ICV (0.4 mg) significantly reduced food intake in pigs feeding after 4-h deprivation and its main effect was in the second half of the meal. Naloxone also abolished the effect of ICV dynorphin. It is concluded that dynorphin and related endogenous opioids are involved in the regulation of food intake in pigs.     

Effects of intracerebroventricular injections of 2-deoxy-D-glucose,d-glucose and xylose on operant feeding in pigs

The effects, on operant feeding, of injection into the lateral cerebral ventricle of 50 μmoles CaCl₂, 4 mmoles D-glucose, 2-deoxy-D-glucose (2DG) or xylose, or NaCl, have been studied in five pigs. All the sugars and CaCl₂ were given in 1 ml of normal saline. Each of the sugar solutions produced transient drinking. Only CaCl₂ and 2DG significantly increased food intake during the hour following injection. The results show that the mechanism by which the pig responds to intracerebroventricular 2DG is similar to that of the rat and different from that of the sheep.     

Operant feeding and drinking in pigs following intracerebroventricular injection of synthetic cholecystokinin octapeptide

Operant feeding and drinking was investigated in food- or water-deprived pigs following intracerebroventricular (ICV) injection of a saline solution containing synthetic cholecystokinin (CCK) octapeptide. In 17-hour food-deprived animals treated with 0, 5, 10, 20 or 40 units ICV, post-treatment food intake was significantly reduced in a dose-related manner but drinking was unaffected. In 22-hour water-deprived pigs treated with 0, 10 or 40 units CCK octapeptide ICV, no effect on drinking was apparent. Pigs injected intravenously with 40 units following 17 hours food deprivation did not reduce their food intake.     

Electrical activity and feeding correlates of intracranial hypothalamic injection of GABA, muscimol and picrotoxin in the rats

Assemblies of electrodes and a cannula were stereotaxically implanted in the ventromedial (VMH), lateral (LHA) and paraventricular (PVH) hypothalamic areas in male albino rats. Electrical activity of these regions was recorded electrographically before and following intracranial injection (ICI) of GABA, muscimol and picrotoxin. In another set of animals, food intake and water intake were also measured. The activity of the ventromedial hypothalamus changed from slow to fast after ICI of GABA and picrotoxin and fast to slow after muscimol. The activity of the lateral hypothalamus changed from slow to fast with ICI of muscimol and picrotoxin and from fast to slow with GABA, while that of the paraventricular hypothalamic nucleus changed from slow to fast with ICI GABA and fast to slow with muscimol and picrotoxin. ICI of GABA into VMH and LHA and muscimol in VMH, LHA and PVH caused a decrease in food intake. Water intake was also decreased after ICI of GABA in PVH and muscimol in LHA and PVH. On the opposite picrotoxin increased food intake in VMA and LHA and water intake in PVH. The possible interaction of GABAergic drugs with the areas of the brain controlling feeding and drinking is being discussed.     

Turning behaviour induced by injection of muscimol or picrotoxin into the substantia nigra demonstrates dual GABA components.

Injection of the GABA agonist muscimol into rat caudal substantia nigra caused contralateral turning, whereas injection into the rostral substantia nigra caused ipsilateral turning. The GABA antagonist picrotoxin had the opposite effect. These findings support the hypothesis that GABA has dual actions in the substantia nigra. Ipsilateral turning induced by injection of muscimol into rostral nigra was abolished by haloperidol pretreatment, indicating the involvement of dopaminergic mechanisms. Haloperidol pre-treatment did not prevent turning induced by muscimol injected into the caudal nigra, supporting the existence of a non-dopaminergic nigral output system.     

Centrally-administered bombesin produces effects unlike short-term satiety in operant feeding pigs

The effects of intracerebroventricular injections of 0, 1.25, 2.5 or 5.0 μg Bombesin (BBS) on operant feeding and of 0, 1.25 or 2.5 μg BBS on operant drinking were examined in pigs deprived of food and water for 17 hours. BBS reduced foor or water intake, depending on which reinforcer had been withheld. BBS also produced behavioural patterns not typical of normal satiety in this species.     

Stimulation of feeding in the satiated pig by intracerebroventricular injection of neuropeptide Y

Operant feeding and drinking were studied in satiated pigs following injection of 0 (saline vehicle control), 25, 50 or 100 micrograms neuropeptide Y into the lateral cerebral ventricles. Neuropeptide Y stimulated feeding in a dose related manner without any apparent aversive effects. No facilitation of drinking was observed.     

Effects of GABA agonists on Herxheimer microshock in guinea pigs

In this paper we describe the first observation of GABA inhibition in an experimental model of asthmain vivo. Guinea-pigs were actively sensitized with ovalbumin i.p. and 20 days later the Herxheimer microshock was performed. GABA and (–)-baclofen injected 20 min previously significantly prevented the development of microshock. Therefore GABAergic drugs appear to modulatein vivo anaphylactic reaction. The value of this observation with regard to the physiopathology and therapy of asthma remains to be elucidated.     

GABA and hypothalamic feeding systems. I. Topographic analysis of the effects of microinjections of muscimol

When carried out in 7–8 day old rats housed in grouped condition following weaning, bilateral amygdaloid lesions provoke a lasting hyperreactivity in terms of increased locomotor activity and higher rearing scores in the openfield. The lesion-induced hyperreactivity which is clearly apparent at 40 days and which persists till adult age, is less marked if the weaned rats are housed in isolation. When carried out at the age of 25 days, amygdaloid lesions enhance even more the rat's responsiveness to a novel environment. Early amygdaloid lesions provoke a marked increase in the proportion of rats that display mouse-killing behavior when adult, a behavioral effect that can be linked up with their hyperreactivity. On the contrary, bilateral amygdaloid lesions carried out in adult rats (at 3 months of age) do not change their responsiveness in the open-field, and only a small proportion of the lesioned rats (35 percent) spontaneously display mouse-killing behavior. It is concluded from the data obtained that the amygdala is involved in two closely related processes which play an important role in the ontogenetic development of the rat's reactivity and social responses. On the one hand, the amygdala takes an essential part in the setting up of a stable inhibition of aggressive responses on the basis of social interactions; on the other hand, it is involved in mechanisms which progressively lessen in a more general way the organism's reactivity to its environment.     

侧脑室注射链脲佐菌素对大鼠海马神经元突触的影响

为观察链脲佐菌素(streptozotocin,STZ)双侧侧脑室注射对大鼠海马神经元突触的影响,本研究将Wistar大鼠随机分为对照组和模型组,模型组大鼠分别于第1、3d双侧侧脑室重复注射STZ3mg/kg,对照组以人工脑脊液代替STZ。21d后,取大鼠海马,免疫组织化学染色及Western blotting方法观察突触素、活性调节细胞骨架相关蛋白(activity-regulated cytoskeletal-associatedprotein,Arc)的表达;电镜观察海马CA1区神经元突触超微结构的改变。结果显示:与对照组相比,模型组大鼠海马内突触素蛋白表达显著减少,而Arc蛋白表达显著增多;模型组海马CA1区神经毡内突触结构异常,突触小泡聚集增多。以上结果提示:脑室注射STZ可影响大鼠海马突触相关蛋白的表达,引起突触超微结构异常,干扰了神经元突触信号的传导。     

Behavioral effects of intracerebroventricular injection of oxytocin in birds

In addition to playing a role as a hormone, oxytocin (OT) can act as a neurotransmitter. In birds, mesotocin (MT) replaces OT. There is both direct and indirect evidence for behavioral effects of OT in rats and humans, but there have been no such studies performed in birds. The purpose of this study was to define the effect of intracerebroventricular (i.c.v.) injection of OT (0-10 microg) on locomotion and feeding behaviors of broiler cockerels. Stepping and wing flapping were increased dose-dependently, but OT decreased preening. The i.c.v. injection of OT also caused a dose-dependent decrease in feed intake, feeding time and pecking frequency. These results suggest that OT might play a unique role in inducing a state of arousal in chickens that resembles fear/anxiety and also in reducing feed intake by acting on MT and/or vasotocin receptors.     

DNA damage after intracerebroventricular injection of ouabain in rats

There is an emerging body of data suggesting that bipolar disorder is associated with DNA damage. Intracerebroventricular (ICV) administration of ouabain in rats results in manic-like alterations. We evaluated DNA damage of peripheral blood, cerebrospinal fluid and hippocampus of rats after ICV ouabain injection. Ouabain-induced hyperlocomotion was examined in an open field. Additionally, we used single cell gel electrophoresis (comet assay) to measure early transient damage in cerebrospinal fluid (CSF), hippocampus and blood; and the micronucleus test to measure persistent damage in total blood samples of rats after ouabain administration. Our findings demonstrated that ouabain induced hyperlocomotion in rats, and this response remained up to 7 days following a single ICV injection. In addition, we observed that the persistent increase in the rat spontaneous locomotion is associated with increased hippocampal and peripheral index of early DNA damage in rats. No significant alterations were observed in the micronucleus frequency in total blood samples of the rats after the ouabain ICV injection. These results suggest that ouabain may induce peripheral and central early DNA damage, but this early damage may be repaired.     

Effects of the 5-HT1A receptor agonist 8-OH-DPAT on operant food intake in food-deprived pigs.

The effects of the 5-HT1A agonist 8-hydroxy-2 (di-n-propylamino)tetralin (8-OH-DPAT) were investigated on operant food intake in food-deprived pigs. In Experiment 1, 8-OH-DPAT (5-20 microg/kg) administered intravenously (i.v.) 15 min prior to the occurrence of feeding produced a dose-related decrease in operant food intake in pigs that had been fasted overnight. The effects were mainly apparent during the first 30 min after the start of the feeding period. In Experiment 2, 8-OH-DPAT (25 and 50 microg/kg, i.v.) administered 60 min prior to the occurrence of feeding in pigs that were fasted overnight also produced significant decreases in food intake. The effects were mainly apparent during the first 30-40 min after the start of the feeding period. In Experiment 3, 8-OH-DPAT (20 microg/kg, i.v.) significantly increased operant feeding in satiated pigs during the first 30 min after administration. These results show that 8-OH-DPAT has complex effects on feeding behaviour in pigs, increasing operant food intake in satiated pigs, while producing a reduction in food intake in food-deprived animals.     

Changes in heart rate during suppression of operant responding in pigs

Three groups of four pigs were subjected to a conditioned emotional response (CER), a time-out and a punishment procedure, each involving a discrimination between a positive and a negative conditioned stimulus. In the CER group and in the punishment group, pigs soon learned to suppress responding during the CS+, showing at the same time a marked bradycardia. Pigs in the time-out situation showed no consistent changes in heart rate although a marked decrease occurred in response rate. In all the conditioning procedures a clear discrimination was demonstrated between the CS+ and CS?. The results are interpreted in terms of interference between heart rate and general activity.     

Effect of chronic intracerebroventricular morphine to feeding responses in male rats

Stainless steel cannulae were implanted stereotaxically in the third ventricle of male albino rats. The rats were fed with natural food pellets and water ad lib. After seven days of cannulation, daily body weight, food intake and water intake were recorded for the first five days, which was considered the preinjection control. Then increased and repetitive injections of morphine sulphate were administered intracerebroventricularly (ICV) in dosage of 30 micrograms/2 microliter, 45 micrograms/3 microliter, 60 micrograms/4 microliter, 75 micrograms/5 microliter, 90 micrograms/6 microliter and 105 micrograms/7 microliter on each following day respectively. In a separate set of experiments, the blood glucose levels were measured in animals injected with morphine to a dose corresponding to 15 micrograms/1 microliter, 30 micrograms/2 microliter, 45 micrograms/3 microliter, 60 micrograms/4 microliter and 75 micrograms/5 microliter on days 1, 2, 3, 4 and 5 respectively. Statistically significant (p less than 0.001) decreases in the body weight, food intake, water intake and increase in blood glucose were observed. The inferences derived from the above observations for the possible involvement and interaction of opioids in the regulation of feeding mechanisms have been discussed.     

Effect of GABA muscimol and picrotoxin on electrical activity of the medial preoptic area in unanesthetized rats

Intracranial cannula along with electrodes was stereotaxically implanted in medial preoptic area of male rats. The electrical activity of mPOA was recorded before and after microinjection of GABA (0.5 micrograms/02 microliters), muscimol (0.5 micrograms/0.2 microliter), picrotoxin (0.25 micrograms/0.2 microliter) and their respective controls. Generalized slowing with an increase in amplitude appeared with GABA and muscimol, while picrotoxin produced just the reverse, i.e. fast activity. Thus the mPOA seems to be vulnerable to GABAergic compounds and supports the diversity of physiological and behavioral functions.     

Effects of feeding, fasting and refeeding on growth hormone and insulin in obese pigs

This study has indicated that temporal patterns of plasma GH changes were similar in lean and obese pigs with one to two secretory spikes occurring during a 6-hour period. Fasting caused increased GH in both pig strains; however, obese pigs, compared to lean, had lower GH during feeding and fasting. This depressed plasma GH of obese pigs may not be due entirely to impaired pituitary function since refeeding caused increased GH to levels similar to lean pigs. Insulin response per unit of feed intake was greater in obese pigs compared to lean. Together with higher insulin to glucose ratios, these results indicate hyperinsulinemia in the obese pigs. Overall, hormone and glucose responses were influenced by the nutritive status--fed, fasted or refed. Therefore consideration of feeding schedule was important in assessment of hormonal differences between the lean and obese pigs.     

Intravenous cholecystokinin octapeptide in pigs reduces operant responding for food,water, sucrose solution or radiant heat

The effect of intravenous injections of 0 (Saline vehicle), 10, 20 or 40 units of CCK was studied in pigs performing operant responses for food, water, sucrose solution or radiant heat. In hungry pigs working for food, thirsty pigs responding for water, and non-deprived pigs working for sucrose, 20 and 40 units CCK produced significant dose-related decreases in response rates lasting for about 5 min. In pigs responding for 10 sec bursts of infra-red heat at an ambient temperature of 5°C, 40 units CCK significantly reduced the response rate during the 5 min period following injection.     

Leukotriene B4, administered via intracerebroventricular injection, attenuates the antigen-induced asthmatic response in sensitized guinea pigs

Background  

Despite intensive studies focused on the pathophysiology of asthmatic inflammation, little is known about how cross-talk between neuroendocrine and immune systems regulates the inflammatory response during an asthmatic attack. We recently showed corresponding changes of cytokines and leukotriene B₄ (LTB₄) in brain and lung tissues of antigen-challenged asthmatic rats. Here, we investigated how LTB₄ interacts with the neuroendocrine-immune system in regulating antigen-induced asthmatic responses in sensitized guinea pigs.     

Effects of dietary fibers with different physicochemical properties on feeding motivation in adult female pigs

The satiating effects of dietary fiber may depend more on physicochemical properties of the fiber than on total fiber intake. These properties are expected to affect satiety feelings and feeding motivation due to different effects in the gastrointestinal tract. The aim of the current study was to assess the effects of fibers with varying physicochemical properties (bulkiness, viscosity and fermentability) on feeding motivation in adult female pigs. Sixteen pair-housed pigs received four diets: lignocellulose (LC), pectin (PEC), resistant starch (RS), and control (C) without fiber, in four periods in a Latin square design. Each fiber was fed at a low (L) followed by a high (H) inclusion level (7days each). At 1h, 3h, and 7h after the morning meal, feeding motivation was assessed in an operant test, where turning a wheel yielded multiple food rewards, and in a runway test, where walking a fixed U-shaped track yielded one food reward. Pigs were observed in their home pen for 6h, using 90-s instantaneous scan sampling. In the operant test, throughout the day feeding motivation was higher for pigs on PEC compared with pigs on LC. In the runway, feeding motivation increased particularly at 1h after the meal for pigs on PEC compared with pigs on RS. Also at 7h, feeding motivation tended to decrease for pigs on RS compared with pigs fed other diets. In their home pen, pigs on PEC showed more feeder-directed behavior compared with pigs on RS. In conclusion, PEC was the least satiating fiber. LC and RS, despite a lower supply of available energy, were the most satiating fibers, possibly due to their bulky and fermentation properties, respectively.