Glucose Intake Alters Expression of Neuropeptides Derived from Proopiomelanocortin in the Lateral Hypothalamus and the Nucleus Accumbens in Fructose Preference Rats

To study the neuroendocrine mechanism of sugar preference, we investigated the role of glucose feeding in the regulation of expression levels of neuropeptides derived from proopiomelanocortin (POMC) in the lateral hypothalamus (LH) and nucleus accumbens (NAc) in fructose preference rats. Fructose preference rats were induced by using the lithium chloride backward conditioning procedure. The fructose preference was confirmed by the two-bottle test. The drinking behavior of rats was assessed by the fructose concentration gradient test. The preference of 10% glucose or 0.1% saccharine was assessed, and the expression levels of neuropeptides derived from POMC in the LH and the NAc in fructose preference rats were measured by Western blot analysis. Fructose preference rats displayed a greater fructose preference than control rats. Furthermore, fructose preference rats preferred glucose solution rather than saccharine solution, while control rats preferred saccharine solution rather than glucose solution. The expression levels of neuropeptides derived from POMC in the LH and the NAc were changed by glucose but not saccharine intake. In summary, the data suggests that glucose intake increases the expression of neuropeptides derived from POMC in the LH and the NAc in fructose preference rats.

Fluoxetine stimulates anti-inflammatory IL-10 cytokine production and attenuates sensory deficits in a rat model of decompression sickness

Despite “gold standard” hyperbaric oxygen treatment, 30% of patients suffering from neurological decompression sickness still exhibit incomplete recovery, including sensory impairments. Fluoxetine, a well-known antidepressant, is recognized as having anti-inflammatory effects in the setting of cerebral ischemia. In this study, we focused on the assessment of sensory neurological deficits and measurement of circulating cytokines after decompression in rats treated or not with fluoxetine. Seventy-eight rats were divided into a clinical ( n = 38) and a cytokine ( n = 40) group. In both groups, the rats were treated with fluoxetine (30 mg/kg po, 6 h beforehand) or with a saccharine solution. All of the rats were exposed to 90 m seawater for 45 min before staged decompression. In the clinical group, paw withdrawal force after mechanical stimulation and paw withdrawal latency after thermal stimulation were evaluated before and 1 and 48 h after surfacing. At 48 h, a dynamic weight-bearing device was used to assess postural stability, depending on the time spent on three or four paws. For cytokine analysis, blood samples were collected from the vena cava 1 h after surfacing. Paw withdrawal force and latency were increased after surfacing in the controls, but not in the fluoxetine group. Dynamic weight-bearing assessment highlighted a better stability on three paws for the fluoxetine group. IL-10 levels were significantly decreased after decompression in the controls, but maintained at baseline level with fluoxetine. This study suggests that fluoxetine has a beneficial effect on sensory neurological recovery. We hypothesize that the observed effect is mediated through maintained anti-inflammatory cytokine IL-10 production.

Withdrawal of Presession Saccharin Suppresses Food-Maintained Responding in Rats

Decreased motivation following drug withdrawal is often characterized as indicative of addiction. Similar behavioral disruptions are seen in negative contrast paradigms. In the current study, 7 rats with a history of access to a palatable 0.15% saccharine solution before operant sessions were conditioned. Rats responded for food under a multiple FR 5 FR 40 reinforcement schedule. When presession saccharin was removed and replaced with water, responding maintained by food was significantly decreased, with greater effects observed under the FR 40 schedule. These results support the assertion that behavioral disruptions accompanying withdrawal syndromes include a negative contrast component.

Effect of high-altitude hypoxia on feeding responses and hedonic matrix in rats

Albino male rats (n = 78) were exposed to a simulated high altitude (HA) equivalent to 7,620 m for 6 h daily, contiguously for a period of 21 days, to study their feeding behavior and gustatory responses. Their food, water intake, and body weight were recorded daily, and blood sugar and blood insulin were estimated once a week. All the parameters were recorded for a period of 3 wk each before, during, and after exposure to simulated HA. The results show a decrease in daily food and water intakes and body weight and mild hyperglycemia and hyperinsulinemia during hypoxic exposure. The 1-h single-bottle taste solution test showed a preference for sweet solutions (13% glucose and 0.2% saccharine) over citric acid (0.16%), sodium chloride (0.9%), and quinine sulfate (0.001%) during exposure to simulated HA. The 1-h two-bottle test containing glucose (calories plus taste) and saccharine (taste but no calories) administration showed a preference for the glucose solution over the saccharine solution. The trend of the 1-h intake of all test solutions also showed a reversal to preexposure levels after termination of HA hypoxia. It would appear that high-altitude stress influences food intake in a manner that sensory cues (e.g., preference for sweet substances) become more important.

Effects of Bilateral Amygdala Lesions on Neophobia and Conditioned Taste Aversion in Mice

The effects of bilateral lesions of the basolateral amygdala on the neophobia to a novel solution and on the conditioned taste aversion were investigated in 35 male CFW mice. Analysis of consumed saccharine solution showed that the amygdala lesions in mice diminished the neophobia and conditioned taste aversion. These findings were consistent with previous data from rats and suggested that amygdala is an important area for processing gustatory information in mice.

Positive Incentive Contrast as a Function of Age and Length of Training in Rats

Exp. I demonstrated that positive incentive contrast effects in an operant conditioning chamber produced by an increase in the concentration of a saccharine solution in 30 180-day-old rats (older animals) are not found in 30 25-day-old rats (younger rats). Exp. II indicated that the probability of obtaining positive contrast with 60 male albino rats is a positive function of the length of the preshift period.

Electrical effects accompanying the decomposition of organic compounds. II.- Ionisation of the gases produced during fermentation

It is well known that the gases liberated during certain chemical actions carry charges of electricity. Thus Lavoisier and Laplace found that the hydrogen liberated from the action of hydrochloric acid upon iron is charged positively. More recently Enright (1) has noted the same effect, and Townsend (2) has shown that the gases liberated during electrolysis are also charged. Ina previous paper (3) evidence has been brought forward to show that the decomposition of organic matter gives rise to electrical effects which are of the same nature as those produced by the action of acids upon metals. It seemed therefore an interesting point to investigate whether the CO 2 escaping from the fermentation of a saccharine solution might carry an electric charge and be ionised. To determine this point a series of experiments were carried out by the employment of a good leaf electroscope and a Dolezalek electrometer. The method adopted was to suspend a metal plate with rolled edge a few centimeters above of the surface of glucose undergoing fermentation through the action of yeast, the metal plate being connected with the electroscope or electrometer, and the whole suitably screened in a box lined with tinfoil. Readings were then taken in the ordinary manner.