The water binding behavior of kappa-carrageenan determined by three different methods.

kappa-Carrageenan is a biopolymer extracted from red seaweeds which has been in the focus of pharmaceutical development for many years. Most applications make use of the large water binding capacity of kappa-carrageenan. The primary limitation of kappa-carrageenan is the variation in the substance quality. Therefore, the water binding capacity of different kappa-carrageenan products was investigated by dynamic vapor adsorption, freezing and non-freezing bound water and water retention value. The kappa-carrageenans were observed to have a higher water binding capacity than microcrystalline cellulose (MCC) in all three methods. The amount of adsorbed water is similar for all carrageenans. Differences between the carrageenan types (kappa, iota, and lambda) were remarkable for the freezing bound water and centrifugation bound water as well as between the kappa-carrageenans of different suppliers.

The effects of acute and repeated restraint stress on the nociceptive response in rats.

The effects of acute and repeated restraint stress on nociception, as measured by the tail-flick latency, were studied in adult male and female rats. After the exposure to a single restraint session, both male and female rats presented an increased latency in the tail-flick test. On the other hand, chronically stressed females presented a performance similar to the control group, whereas chronically stressed male rats responded to restraint with a decrease in the tail-flick latency. This response could be determined by the chronic treatment itself or by the restraint done just before the measurement. Thus, the effect of chronic stress upon basal tail-flick latency was evaluated. In male rats, this latency was significantly decreased in the stressed animals compared with the control group. In female rats, no difference between those groups was observed. Therefore, the results suggest that: (a) acute restraint stress induces an analgesic response in both male and female rats, and (b) there is a gender-specific nociceptive response induced by repeated restraint stress with a hyperalgesic effect in response to stress only in males.

Effect of restraint stress on feeding behavior of rats.

The expression of appetite reflects the complex functioning of a psychobiological system organized in different levels closely related to each other, in which emotional changes can influence feeding behavior. Benzodiazepines are widely used as anxiolytics and can change behaviors caused by stress. The aim of the present study was to verify the feeding behavior of rats, submitted or not to fasting, after acute and chronic restraint stress. We also evaluated the response to the ingestion of sweet food of chronically restrained animals after the administration of diazepam. Male adult Wistar rats were exposed to restraint 1 h/day for 50 days in the chronic model. In the acute model, there was a single exposure. Four hours after the stress, the animals were placed in a lightened area in the presence of 10 pellets of sweet food (Froot Loops). The number of ingested Froot Loops was measured during a period of 3 min in the presence or absence of fasting. The groups acutely stressed showed ingestion similar to that of the control group, whether they had been fasted or not. The chronically stressed animals showed increased ingestion of sweet food. Diazepam given 60 min before the test session of the stressed rats reduced the ingestion of these animals to control levels. Thus, the chronic stress increases appetite for sweet food, independently of hunger, and diazepam is able to reverse this behavior.