The role of central and peripheral cholecystokinin in mediating appetitive behaviors

Cholecystokinin (CCK) reduces total food consumption in mice, rats, pigs, sheep, monkeys and humans. Behaviors associated with an underlying state of satiety are reported after CCK administration. Reductions in exploration and social interactions by CCK are not due to true sedation or sleep, as measured by cortical EEG recordings. The satiety effects appear to be mediated by peripheral CCK receptors, through a feedback loop involving the vagus nerve. The conceptual link between the behavioral functions of CCK as a putative satiety signal and its established digestive functions are discussed.     

Aspects of central and peripheral regulation of reproduction in mammals

To increase our knowledge concerning the central and peripheral regulation of reproduction in mammals a series of studies were performed. In the first experiment, we found that exogenous leptin altered the activity of the hypothalmo-pituitary-gonadotropic axis in sheep during insufficient feeding. The action of leptin appears to be mediated by changes in GnRH and LH secretion as well as NPY immunoreactivity. The aim of the second experiment was to investigate the role of the adipoinsular axis hormones during pregnancy in rats. The elevated levels of plasma leptin as wells as the increased mRNAs expression of the leptin receptors in placenta indicate the significant role of the hormone in fetal growth and development. On the other hand, a decrease in leptin receptors mRNA content within hypothalamus and pituitary together with unchanged plasma insulin level may suggest that during rat pregnancy leptin resistance was developed in the hypothalamus, pituitary and pancreatic islets. The third experiment was carried out to establish the role of opioids and glucocorticoids in the regulation of the hypothalmo-pituitary-gonadal axis in ewes during natural or synchronized estrous cycle. Prolonged treatment with progesterone resulted in significant changes in plasma levels of Met-enkephalin, cortisol and steroids and altered the expression of proenkephalin mRNA in the hypothalamus, pituitary, ovary and adrenals. Injections of Met-enkephalin or naltrexone (blocker of opioid receptors) modulated the progesterone influence in tested tissues. The data clearly suggest that opioids are involved in the regulation of the estrous cycle at the hypothalamo-pituitary-gonadal/adrenal axes.     

Diabetes-induced biochemical changes in central and peripheral catecholaminergic systems

A great variety of alterations have been described in the nervous system of diabetic animals. They are named as diabetic neuropathy and affect the brain, spinal cord and peripheral nerves. In diabetic animals, plasma and tissue catecholamine levels have been reported to be increased, decreased or unchanged, and these disparities have been explained by differences in the tissues selected, severity or duration of diabetes. Dopamine, norepinephrine and epinephrine from different tissues were extracted by absorption onto alumina, and measured by high performance liquid chromatography with electrochemical detection. We found that diabetes alters catecholaminergic systems in a highly specific manner. The dopamine content is reduced in the dopaminergic nigrostriatal system only. Norepinephrine is differently altered in several areas of the sympathetic nervous system. It is increased in cardiac ventricles, and decreased in stellate ganglia and the blood serum. However, it is not altered in the central nervous system. Finally, epinephrine is only altered in the adrenal gland where it is increased, and in the serum where it is reduced. Our results suggest that diabetes reduces the activity of the nigrostriatal dopaminergic system. Changes found at the sympathoadrenal level could be explained by reduced norepinephrine and epinephrine synthesis, with increased storage due to a reduced release from synaptic vesicles.     

The role of serotonergic system in body temperature regulation.

Results indicate that vascular responses to temperature stimulation are predominantly impaired in animals with 5-HT deprivation. A hypothesis is therefore raised that the 5-HT system participates in body temperature regulation in such a way as to link the regulatory output with vasomotor pathways. The 5-HT system in the spinal cord has been shown to inhibit the afferent transmission of temperature signals. Therefore, depletion of 5-HT does not prevent sensory transmission, at least at the spinal cord level.     

The central role of the haemolymph in the regulation of nutrient intake in insects

Abstract. A synthesis is presented for the control of nutrient intake in insects. The haemolymph plays a central role and provides a constantly updated summary of nutritional state. Various ways are discussed in which haemolymph parameters are directly and indirectly linked to the three key aspects of feeding behaviour: food location, food selection and ingestion.     

The role of corticosterone in supporting migratory lipogenesis in the dark-eyed Junco, Junco hyemalis: a model for central and peripheral regulation

The functional role of corticosterone (CORT) in regulating migratory hyperphagia and lipogenesis was investigated in an annual migrant, the dark-eyed junco (Junco hyemalis). Intraperitoneal injections of either dexamethasone (9 microg DXM/500 microL of 5% EtOH in saline, n=10) to inhibit an increase in baseline CORT or saline (5% EtOH, n=9) were given every 48 h for 15 d after transfer from short (10.5L:13.5D) to long (15.5L:8.5D) days. Food intake, body mass, furcular fat deposition scores, and nocturnal migratory activity were recorded for 29 d after photostimulation. Both groups showed the same increase in daily food intake over the study period (DXM=52%, control=41%). Controls began to increase baseline CORT and mass about 2 wk after photostimulation. DXM-treated birds maintained low CORT and did not increase mass or CORT until injections ceased, at which time they gained mass at the same rate shown earlier by controls. DXM-treated birds did not show greater levels of migratory activity despite experiencing an increase in energy intake during the CORT-inhibited period. Collectively, the results support the migration modulation hypothesis, illustrating how an increase in baseline CORT is needed to support the development of migratory condition. We address the apparent conflict with earlier studies on CORT and migratory food intake and propose a model in which migratory hyperphagia is supported by changes in centrally regulated responses to CORT that can occur even if CORT remains low and lipogenesis is regulated predominantly by peripheral mechanisms that require an increase in baseline CORT.     

Appetite regulation: The central role of melatonin in Danio rerio

Melatonin is the hormonal mediator of photoperiodic information to the central nervous system in vertebrates and allows the regulation of energy homeostasis through the establishment of a proper balance between energy intake and energy expenditure. The aim of this study was to evaluate the role of melatonin in appetite central control analyzing the involvement of this hormone in the regulation of feeding behavior in the zebrafish Danio rerio. For this purpose, the effect of two different melatonin doses (100 nM and 1 μM) administered for 10 days, via water, to zebrafish adults was evaluated at both physiological and molecular level and the effect of melatonin was considered in relation to the most prominent systems involved in appetite regulation. For the first time, in fact, melatonin control of food intake by the modulation of leptin, MC4R, ghrelin, NPY and CB1 gene expression was evaluated.The results obtained indicate that melatonin significantly reduces food intake and the reduction is in agreement with the changes observed at molecular level. A significant increase in genes codifying for molecules involved in feeding inhibition, such as leptin and MC4R, and a significant reduction in the major orexigenic signals including ghrelin, NPY and CB1 are showed here.Taken together these results support the idea that melatonin falls fully into the complex network of signals that regulate food intake thus playing a key role in central appetite regulation.     

The dual role of temperature in the regulation of the seasonal changes in dormancy and germination of seeds of Polygonum persicaria L.

Summary The role of temperature in the regulation of seasonal changes in dormancy and germination was studied in seeds of Polygonum persicaria. Seeds were buried in the field and under controlled conditions. Portions of seeds were exhumed at regular intervals and germination was tested over a range of conditions. Seeds of P. persicaria exhibited a seasonal dormancy pattern that clearly showed the typical features of summer annuals, i.e. dormancy was relieved at low winter temperatures, the germination peak occurred in spring and dormancy was re-induced in summer. The expression of the dormancy pattern was influenced by the temperature at which germination was tested. At 30°C exhumed seeds germinated over a much longer period of the year than at 20° or 10°C. Nitrate added during the germination test occasionally stimulated germination. The seasonal changes in dormancy of buried seeds were regulated by the field temperature. Soil moisture and nitrate content did not influence the changes in dormancy. The fact that, on the one hand, field temperature determined the changes in dormancy and, on the other hand, germination itself was influenced by temperature, was used to describe the seasonal germination pattern of P. persicaria with a model. Germination of exhumed seeds in Petri dishes at field temperature was accurately described with this model. Germination in the field was restricted to the period where the range of temperatures over which germination could proceed (computed with the model) and field temperature overlapped.     

Adaptive changes of locomotion after central and peripheral lesions

This paper reviews findings on the adaptive changes of locomotion in cats after spinal cord or peripheral nerve lesions. From the results obtained after lesions of the ventral/ventrolateral pathways or the dorsal/dorsolateral pathways, we conclude that with extensive but partial spinal lesions, cats can regain voluntary quadrupedal locomotion on a treadmill. Although tract-specific deficits remain after such lesions, intact descending tracts can compensate for the lesioned tracts and access the spinal network to generate voluntary locomotion. Such neuroplasticity of locomotor control mechanisms is also demonstrated after peripheral nerve lesions in cats with intact or lesioned spinal cords. Some models have shown that recovery from such peripheral nerve lesions probably involves changes at the supra spinal and spinal levels. In the case of somesthesic denervation of the hindpaws, we demonstrated that cats with a complete spinal section need some cutaneous inputs to walk with a plantigrade locomotion, and that even in this spinal state, cats can adapt their locomotion to partial cutaneous denervation. Altogether, these results suggest that there is significant plasticity in spinal and supraspinal locomotor controls to justify the beneficial effects of early proactive and sustained locomotor training after central (Rossignol and Barbeau 1995; Barbeau et al. 1998) or peripheral lesions.     

The role of the central nervous system functional condition in formation of responses of visual analyser's peripheral and central parts

Nembutal was shown to inhibit formation of early receptor potentials, "a"-wave and oscillatory potential of the retina (ERG), as well as the oscillatory potentials of the superior colliculus and visual cortex. The first oscillatory potential of the retina alone was enhanced. Aminazin exerted rather an opposite effect related, probably, to facilitation of the retina and central structures due to elimination of a constant inhibitory effect of the brain stem RF.     

The role of endogenous opiates in thermal regulation of the body during exercise.

Naloxone abolished the rise in body temperature seen after bicycle ergometer tests performed by 10 healthy men. This suggests that endogenous opiates play a part in thermal regulation during muscular exercise.     

The role of GTP in the regulation of two forms of AMP deaminase from chicken kidney

1. Two molecular forms of AMP deaminase have been revealed by phosphocellulose column chromatography of the chicken kidney extract. 2. The chromatographic, kinetic and regulatory properties of these two forms were similar to these of two enzyme forms previously found in the chicken liver, lizard liver and in rat small intestine. 3. GTP exerted different effect from MgGTP on the activity and kinetic parameters of both AMP deaminase I and II from chicken kidney.