Electrophysiological dysfunction induced by anti-ribosomal P protein antibodies injection into the lateral ventricle of the rat brain.

Objective Anti-ribosomal P antibodies (anti-P) are strongly associated with neuropsychiatric lupus. This study was designed to determine whether these antibodies are capable of causing electro-oscillogram (EOSG) and behavior alterations in rats. Methods IgG fraction anti-P positive and affinity-purified anti-P antibodies were injected intraventricularly in rats. Sequential cortical and subcortical EOSGs were analyzed during 30 days. IgG anti-Ro/SS-A and normal IgG were used as controls. Results All 13 animals injected with IgG anti-P demonstrated a high prevalence of polyspikes, diffusely distributed in hippocampal fields and cerebral cortex. These abnormalities persisted approximately a month. Remarkably, an identical electrical disturbance was observed with the inoculation of affinity-purified anti-P antibodies. The EOSG alterations were associated with behavioral disorders with varying degrees of severity in every animal injected with anti-P. In contrast, no changes in EOSG or behavioral disturbances were observed in the control group. Conclusion Our study indicates that anti-P antibodies can directly induce electrophysiological dysfunction in central nervous system particularly in hippocampus and cortex associated with behavior disturbances.

Anxiety and high plasma catecholamines do not impair pharmaco-induced erection of psychogenic erectile dysfunctional patients.

The aim of this study was to assess the influence of anxiety and plasma catecholamines on the pharmaco-induced erection of psychogenic erectile dysfunction (ED) patients. A total of 23 patients with psychogenic ED aged from 19 to 43 y were submitted to: (1) anxiety evaluation by the Spielberger's State and Trait Anxiety Inventory-STAI; (2) intracavernous injection of PGE1 10 microg+phentolamine 1 mg with the response monitored by Rigiscan; (3) blood sampling from cavernous bodies and cubital vein for adrenaline and noradrenaline levels determination by high performance liquid chromatography. The whole procedure was done in a single clinical setting at the same day. We found no significant correlation between the erection rigidity and the cavernous or peripheral catecholamines or between erection rigidity and anxiety scores. Some patients showed rigid erections despite high anxiety scores or penile catecholamine levels while others, with incomplete erections, had much smaller levels. These results are suggestive of a more complex mechanism controlling the penile sympathetic responsiveness in psychogenic ED patients.

Effect of chemical stimulation of the dorsomedial hypothalamic nucleus on blood plasma glucose, triglycerides and free fatty acids in rats.

The effects of chemical stimulation of the dorsomedial hypothalamic nucleus (DMH) on blood plasma concentration of glucose, triglycerides, insulin, and free fatty acids (FFA) were investigated in anesthetized adult Wistar rats. Microinjection of 12.5 nmol of norepinephrine into the DMH increased blood plasma concentration of glucose and FFA, decreased triglycerides, and did not change plasma insulin within 5 min; after 20 min, blood glucose and FFA reached control values. Microinjection of epinephrine (12.5 nmol) into the DMH also increased blood plasma glucose concentration and decreased triglycerides after 5 min. These effects are probably mediated by beta-adrenergic mechanisms, because they were prevented by beta-adrenergic antagonist propranolol, but not by alpha-adrenergic antagonist prazosin. Microinjection into the DMH of glutamate, dopamine, or acetylcholine failed to cause any change in those metabolic parameters, corroborating the hypothesis that the DMH is part of a beta-adrenergic pathway involved in short-term modulation of the availability of glucose and FFA.

Increase of food intake induced by glucagon in the rat.

The effect of intraperitoneal administration of saline, glucose (25 mg/100 g b.w.), insulin (0.025 U/100 g b.w.) and glucagon (50 micrograms/kg b.w.) on glycemia, liver glycogen concentration and food intake was studied on 104 male adult Wistar rats. When saline was injected the amount of food ingested was similar to that expected at the metabolic moment selected for the tests. Glucose administration did not reduce food intake but both insulin and glucagon provoked a threefold increase during the 60 minutes ensuing the injection. The overall ingestion of food during the 24 hours after the injection of the hormones was significantly higher (about 10%) than the control values during the preceding or the succeeding 24 hours. A hyperphagic, rather than a hypophagic effect of glucagon administration is possibly related to the small dose used in the experiments. The mechanisms involved in the increase of food intake due to glucagon are discussed in terms of acceleration of the metabolic reactions that normally prevent large drops of glycemia as glucose utilization proceeds during the inter-meal periods and that in physiological conditions build up until the need for food arises.

Meal-feeding and physical effort. 1. Metabolic changes induced by exercise training.

To evaluate the consequences of the combination of meal-feeding (which causes in the long term several adaptations that lead to saving stored energetic substrates), rats subjected to a 2-hr feeding/22-hr fasting schedule were forced to swim 30 min everyday at a fixed hour during four weeks. The results indicate that meal-fed exercised rats: 1) increase food intake above that found in the nonexercising and the corresponding (nonfood-restricted) controls; 2) did not lose weight (in contrast to the controls); 3) initially had a high glycogen mobilization but at the end of the fourth week started to save hepatic glycogen again, despite the intense energy demanding exercise; 4) maintained a slight hyperglycemia; 5) mobilized less free fatty acids than the nonexercising meal-fed rats, probably due to higher insulinemia; 6) had a lower content of ascorbic acid in the adrenal glands in comparison to the control exercising rats; this suggests that the exercise was less stressful in the latter group.

Meal-feeding and physical effort. 2. Metabolic changes induced by an acute exercise.

In this study, rats under meal-feeding up to four weeks were submitted to a sudden exercise (swimming) to evaluate the effects of a behavior that requires mobilization of a large amount of energy on some physiological parameters already changed due to the chronic food-restriction. During exercise meal-fed rats: 1) increase the rate of gastric emptying; 2) maintain glycemia more steadily than the controls even during a long-lasting exercise; 3) maintain high liver glycogen concentration and its mobilization starts later on; 4) free fatty acid mobilization is lower than in the controls but during exercise do use much more; 5) keep more glycogen in the muscles (including the heart) than the controls but during the exercise do utilize much more; 6) are slightly less stressful (mainly after a longer exercise) than the controls as suggested by the adrenal ascorbic acid content.

Carbohydrate metabolism and food intake in food-restricted rats. Relationship between the metabolic events during the meal and the degree of food intake.

To study some metabolic features during feeding in food-restricted rats two groups of animals were maintained on a 2 hr feeding/22 hr fast schedule. Group D (n = 38) received a meal every day from 8:00 to 10:00 a.m. Group N (n = 34) was given the meal from 8:00 to 10:00 p.m. The average total amount of food ingested by rats of group N in the two hour period was 6.3 +/- 0.4 whereas Group D ingested 4.8 +/- 0.3 g/100 g b.w. The metabolic pattern also was different in one group as to the other. The basal liver glycogen content when feeding started was considerably lower in the nocturnal group (0.14 +/- 0.02 mg/100 mg of liver tissue) than in the diurnal group (0.44 +/- 0.10 mg/100 mg). Afterwards glycogen increased in both groups but more steeply and intensely in group N. Glycemia increased in group D and was almost invariant in group N. Insulinemia went up in both groups but in group D its peak was higher and occurred 60 minutes after the onset of feeding whereas the peak in group N was much lower and occurred at 90 minutes. There was a clear dissociation between the time courses of insulinemia and glycemia in both groups, especially in group N, which suggests a central control of insulin secretion during feeding that partially unlocks it from blood glucose concentration. The hepatic glycogen content was partially linked to the amount of food ingested but again there was a dissociation between these two variables, inasmuch as a higher glycogen replenishment in the nocturnal group corresponded to a larger food intake.

Reversibility of metabolic changes induced by feeding schedule in rats.

This study aimed to investigate the effect of free-feeding on rats kept on meal-feeding schedule for a prolonged period. Thus, rats meal-fed for 4 and 20 weeks were given free access to food for subsequent 5 weeks. The metabolic adaptation of higher hepatic glycogen content, low plasma FFA values and sustained glycemia during 22-hr fast, reported for rats subjected to meal-feeding, completely disappeared after free-eating period. The rate of body weight gain increased as a consequence of the free access to food in both groups but the control values (group with food ad lib all the time) were attained only in rats previously submitted to meal-feeding for the shorter period of time (4 weeks). The findings of this study suggest that the recovery of body weight by meal-fed rats, for the control values, seems to depend on the duration of the meal-feeding schedule and the age when it is imposed.

Metabolic performance of free fed rats subjected to prolonged fast as compared to the metabolic pattern in rats under long term food restriction.

Glycemia, free fatty acids, insulinemia, hepatic glycogen, adrenal ascorbic acid, the amount of food ingested and of feces eliminated, gastric emptying and body weight were measured in two groups of rats of the same age. The F, free fed group was subjected to fast during 22 hours and then had a final meal for two hours. The R rats, subjected to food restriction from one to four weeks, had also a final two hour meal after the regular period of 22 hours with no access to food, and then both groups were treated equally. Coincidently, gastric emptying was more delayed, liver glycogen concentration was highest and glycemia was better maintained in the R than the F rats, particularly after three and four weeks of training. Probably due to their greater dependence upon the more frequent supply of nutrients, the F group had a larger free fatty acids mobilization during fast. Adrenal hyperactivity was induced in both groups and the amount of food ingested progressively increased in the R group and decreased in the F group. In general the metabolic efficiency tended to converge to a similar order of magnitude in both groups of animals by the end of the third week. A delayed gastric emptying seems to be a major factor in the adaptations to food restriction.

Centrally injected atropine reduces hyperglycemia caused by 2-DG or immobilization stress in awake rats.

The physiological significance of central cholinergic neurons was investigated by verifying the effect of previous intracerebroventricular administration of atropine on the hyperglycemia induced by 2-deoxyglucose (2-DG) or by immobilization stress in unrestrained, nonanesthetized rats. Intravenous 2-DG induced a marked increase in plasma glucose that was not affected by atropine injected intracerebroventricularly 30 min before. However, the hyperglycemia induced by intracerebroventricular 2-DG was significantly reduced by previous intracerebroventricular injection of atropine. Immobilization induced a rapid increase of plasma glucose levels that was reduced by about 50% by intracerebroventricular injection of atropine. The increase in plasma lactate induced by intravenous 2-DG, or immobilization, was not significantly affected by previous intracerebroventricular injection of atropine. The data suggest that central cholinergic neurons participate in the complex neural events responsible for the hyperglycemic response to neurocytoglucopenia and to stressful situations.

Time course of insulin, corticosterone and metabolic changes caused by lesion of the ventromedial hypothalamus in the rat.

The time course of changes in glycemia, insulinemia, corticosteronemia, liver glycogen, food intake, body and stomach's fresh weight were studied in rats subjected to electrolytic bilateral destruction of the ventromedial hypothalamus (VMH) and in a sham-operated (SO) group. Some of these parameters were determined during the first four hours after lesioning and all were measured also up to two weeks. Glycemia increased steadily, attaining 37.1% 120 min post-lesioning, and a parallel decrease (51.3%) in hepatic glycogen was observed. Twenty minutes after VMH destruction the insulin levels were 215.8% higher than in the SO group, a difference that was reversed 220 min later. At the first day post-lesioning the insulin levels increased 348%. It is suggested that the release was stimulated by the early reflex insulin secretion elicited by food ingestion. During the first hours after VMH lesioning corticosteronemia was elevated to 253.9% of the corresponding parameter in the SO group. When the effects of the lesion were followed up during fifteen days it was found that glycemia and hepatic glycogen returned to normal levels but insulinemia went up again. Plasma insulin increased 325.9% by the end of the observation period while corticosteronemia was 404.5% higher as compared with the SO animals. Food intake increased 63.5% on the day after lesioning and continued to rise, attaining 106% by the fifteenth day, which paralleled the weight gain (31%). A close topographic correlation was found in this study between the precise lesioning of the ventromedial nuclei of the hypothalamus and the changes herein described.

Stationarity and normality of distribution of rat cortical brain waves.

Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is crucial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desynchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms.

Theta waves in the Papez circuit during alertness and dreaming in the rat.

An electro-oscillographic study of the hippocampus, thalamic anterior nuclei and cingulate and pericingulate cortical areas was performed in the rat during the wakefulness-sleep cycle. High voltage (usually from 100 to 200 microV) theta waves, oscillating at regular frequencies from 6 to 10 Hz, were found to occur simultaneously in all of these components of the Papez circuit during attentive behavior and dreaming.

Signs of synchronized sleep elicited by local application of leptazol to a circumscribed area of the ventral surface of medulla oblongata in the cat.

Topical application of some drugs to the ventral surface of medulla oblongata has been found to cause changes in blood pressure and respiration and release of vasopressin. In the present investigation, electrophysiological changes induced in the electrocorticogram of cats by drugs applied to this area of the central nervous system were studied. In eight animals kept anesthetized with sodium pentobarbiturate, leptazol (200 mg/ml) was applied bilaterally (20 microliter on each side) to a small area of the rostral portion of medulla oblongata while blood pressure, respiration, the electrocorticogram from the sigmoid gyri, the nictitating membrane and the pupil width were monitored. In some preparations sodium pentobarbiturate was also applied to the same area after leptazol. Within 30 s of leptazol application to the surface, active spindling started in the sigmoid gyri, simultaneously with myosis, relaxation of the nictitating membrane and inhibition of the limb retraction in response to noxious stimulation. All these changes characterize the state of synchronized sleep. Topical application of pentobarbital to the same area suppressed spindling and reversed the other signs of synchronized sleep. The possible intervention of some known hodological systems or of the sleeping factors described by some authors in the genesis of the above phenomena is discussed.

Rostrum movements in desynchronized sleep as a prevalent manifestation of dreaming activity in Wistar rats.

Considering that eye movements express visual dreams in humans and are prominent during desynchronized sleep in cats, monkeys and birds, rostrum movements were investigated in a macrosmatic species, the rat, to assess the hypothesis that, expressing olfactory and tactile (involving the vibrissae) dreams, they would prevail over eye movements. Desynchronized sleep episodes lasted 148.8 +/- 12.4 s, rostrum movements lasted 80.7 +/- 6.9 s and eye movements occurred during 40.4 +/- 3.9 s, all in accordance with the original hypothesis.

Correlation between concomitant theta waves in nucleus reticularis pontis oralis and in hippocampus, thalamus and neocortex during dreaming in rats.

Theta waves, which are the main electrophysiological expression of dreaming activity in many brain structures of rats, often undergo specific changes in voltage and frequency according to the oniric patterns. Much is known about their mechanisms but little is known regarding their origin, which has been ascribed to a specific activation of either the reticular formation or the septal nuclei or nucleus reticularis pontis oralis. In the present study, rats were prepared for chronic recording of the electro-oscillograms of cortical areas 10, 3 and 17, of hippocampal CA1 and CA3 fields, of nucleus reticularis thalami, nucleus reticularis pontis oralis and occasionally of nucleus reticularis caudalis. Head, rostrum, eye and forelimb movements were also recorded, so that the oniric behaviors could be precisely identified. The scatter diagrams and the corresponding correlation coefficients (r) of the voltage of concomitant waves were determined for each possible pair of leads. The potentials were analyzed at a frequency of 256 Hz over a period of 1 to 3 sec. A very high degree of correlation was observed between theta waves in nucleus reticularis pontis oralis, hippocampal fields and nucleus reticularis pontis caudalis; sometimes r approached unity. Although these data cannot be taken as proof of nucleus reticularis pontis oralis being the source of theta waves, they are at least compatible with this hypothesis.

Suppression of the late component of the carotid occlusion reflex by lesion of the medial forebrain bundle in the rat.

1. The pressor response to a prolonged carotid occlusion in the rat has two components: an early, fast increase in blood pressure, and a late, slow and sustained hypertension. Since the second component can be blocked by a disconnecting lesion near the medial side of the medial forebrain bundle, the hypothesis that this complex structure is involved in the integration of the late pressor reflex was tested. 2. The medial forebrain bundle was partially or completely destroyed, or a disconnecting lesion was made to interrupt some of its medially running afferents and/or efferents. Incomplete lesion caused a transient suppression of the second component in 4 rats, whereas complete lesion in 5 rats or probable interruption of the medial efferent pathways in 3 rats led to suppression of the late component when the one-minute occlusion was performed within one hour after the lesion. 3. The data show that the medial forebrain bundle plays an important role in the integration of the late component of the pressor response to prolonged carotid occlusion.

Electro-oscillographic correlation between dorsal raphe nucleus, neocortex and hippocampus during wakefulness before and after serotoninergic inactivation.

Theta rhythm in many brain structures characterizes wakefulness and desynchronized sleep in most subprimate mammalian brains. In close relation to behaviors, theta frequency and voltage undergo a fine modulation which may involve mobilization of dorsal raphe nucleus efferent pathways. In the present study we analyzed frequency modulation (through instantaneous frequency variation) of theta waves occurring in three cortical areas, in hippocampal CA1 and in the dorsal raphe nucleus of Wistar rats during normal wakefulness and after injection of the 5-HT1a receptor agonist 8-OH-DPAT into the dorsal raphe. We demonstrated that in attentive states the variation of theta frequency among the above structures is highly congruent, whereas after 8-OH-DPAT injection, although regular signals are present, the variation is much more complex and shows no relation to behaviors. Such functional uncoupling after blockade demonstrates the influence of dorsal raphe nucleus efferent serotoninergic fibers on the organization of alertness, as evaluated by electro-oscillographic analysis.

Absence-like seizures in adult rats following pilocarpine-induced status epilepticus early in life.

Administration of pilocarpine causes epilepsy in rats if status epilepticus (SE) is induced at an early age. To determine in detail the electrophysiological patterns of the epileptogenic activity in these animals, 46 Wistar rats, 7-17 days old, were subjected to SE induced by pilocarpine and electro-oscillograms from the cortex, hippocampus, amygdala, thalamus and hypothalamus, as well as head, rostrum and vibrissa, eye, ear and forelimb movements, were recorded 120 days later. Six control animals of the same age range did not show any signs of epilepsy. In all the rats subjected to SE, iterative spike-wave complexes (8.1 0.5 Hz in frequency, 18.9 9.1 s in duration) were recorded from the frontal cortex during absence fits. However, similar spike-wave discharges were always found also in the hippocampus and, less frequently, in the amygdala and in thalamic nuclei. Repetitive or single spikes were also detected in these same central structures. Clonic movements and single jerks were recorded from all the rats, either concomitantly with or independently of the spike-wave complexes and spikes. We conclude that rats made epileptic with pilocarpine develop absence seizures also occurring during paradoxical sleep, showing the characteristic spike-wave bursts in neocortical areas and also in the hippocampus. This is in contrast to the well-accepted statement that one of the main characteristics of absence-like fits in the rat is that spike-wave discharges are never recorded from the hippocampal fields.

Contractions of the gastric antrum induced by stimulation of the medial forebrain bundle in the rat.

Glucoreceptors sensitive to cytoglucopenia exist in the medial forebrain bundle of the rat. The selective activation of these receptors provokes an increase in glycemia and gastric secretion. In the present work, we found that stimulation of this diencephalic area in rats also provokes potent gastric contractions. Stimulation with high voltages usually inhibited this effect.