Effects of knife-cut lesions of the medial forebrain bundle in self-stimulating rats.

Unilateral frontal-plane knife-cut lesions were made in the anterior medial forebrain bundle ipsilateral to a lateral hypothalamic self-stimulation electrode. Behavioral effects of the knife cut on self-stimulation reward and operant performance capacity were measured via the reward summation function method. Knife cuts placed at the level of the anterior commissure were ineffective in altering reward or motor/performance capacity, whereas knife cuts just posterior in the caudal lateral preoptic area degraded reward and sometimes impaired motor/performance capacity. In a second experiment, knife cuts placed posterior to the ventral tegmental area were ineffective unless they intruded on the ventral tegmental area itself. Several small knife cuts placed just anterior to the ventral tegmental were effective in reducing self-stimulation reward. The results are discussed in terms of the anatomical substrate of lateral hypothalamic self-stimulation reward and as a first step in a larger mapping study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of lesions in the medial forebrain bundle on three measures of pain sensitivity and noise-elicited startle.

Subjected 137 male Holtzman albino rats to bilateral lesions of the medial forebrain bundle (MFB) or to surgical control procedures. Lesions produced equivalent decreases in paw-lick latency to heat and in jump and high-magnitude-response thresholds to footshock. Flinch and detection thresholds to footshock were also significantly decreased, though the lesion did not alter the magnitude or habituation of noise-elicited startle. Injection of 75 mg/kg serotonin into lesioned Ss returned the high-magnitude-response threshold to normal values but did not affect detection threshold. It is concluded that the increased sensitivity to painful stimuli resulted from the decrease in telencephalic content of serotonin following MFB lesions. Previous exposure of lesioned Ss to footshock resulted in a potentiation of the startle response to noise, further suggesting that the lesion had increased the aversiveness of footshock. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial forebrain bundle lesions: Specific loss of feeding to decreased glucose utilization in rats.

Found that bilateral destruction of the medial forebrain bundle in female Sherman rats eliminated feeding to decreased intracellular glucose utilization (glucoprivation). The deficit was specific. Feeding was enhanced by dietary dilution and reduced by dietary concentration. More was eaten in the cold and less in the heat. The Ss were not differentially sensitive to quinine adulteration. They returned to normal body weight following regimens of gavage or of restricted feeding. Moreover, they did not differ from normal Ss in drinking to various thirst stimuli. It is suggested that the glucoprivic mechanism makes but a minor contribution to the initiation of spontaneous feeding. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrolytic lesions of the cortical and adjacent nuclei in the amygdala differentially influence thresholds for rewarding medial forebrain bundle stimulation.

After electrolytic lesions to the cortical and adjacent amygdaloid subnuclei, thresholds for rewarding medial forebrain bundle (MFB) stimulation were tracked in 19 rats with bilateral implants and 8 with single implants. Results were categorized into 3 groups depending on the magnitude of the lesion effect on ipsilateral frequency thresholds: substantial (> 60%), small (> 26%), or none (     

Altered sensitivity to footshock after selective serotonin depletion: Comparison of electrolytic lesions and neurotoxin injections in the medial forebrain bundle of the rat.

Compared the changes in 183 male albino rats' jump threshold with changes in monoamine content of the telencephalon after damage to the lateral hypothalamus produced either by electrolytic lesions or by 6-hydroxydopamine (6-OHDA) and 5,7-dihydroxytryptamine (DHT). Electrolytic lesions produced significant decreases in jump threshold and in telencephalic content of serotonin, norepinephrine, and dopamine. Infusions of DHT, with or without pretreatment with desipramine, always reduced both jump thresholds and serotonin content, even when there was no effect on norepinephrine or dopamine. In contrast, 6-OHDA had no effect on jump thresholds or serotonin content, even though both norepinephrine and dopamine were greatly reduced. Results suggest that the increased sensitivity to footshock was solely due to the interruption of ascending serotonergic pathways within the lateral hypothalamus and was not a result of damage either to norepinephrine and dopamine pathways or to some other neural system. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of medial and lateral lesions in the amygdala on fixed-ratio performance.

Trained 18 male albino Wistar rats with medial or lateral lesions in the amygdala to respond on progressively increasing fixed-ratio schedules of reinforcement. Results indicate that medial lesions produced an earlier breakdown of responding, and lateral lesions produced perseveration of response. Interpretations of the data in terms of motivational effects and excitatory and inhibitory functions are discussed. (French summary) (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of perirhinal cortex ablation and crossed unilateral lesions of the medial forebrain bundle from the inferior temporal cortex in the rhesus monkey: Effects on learning and retrieval.

Seven monkeys learned new object-reward associations and scene problems and were overtrained on 100 problems of each type. Four monkeys received crossed lesions of the medial forebrain bundle (MFB) and inferior temporal cortex, with the later addition of a fornix section ipsilateral to the MFB lesion. The remaining 3 monkeys received bilateral perirhinal cortex ablation. Disconnection of the MFB from the inferior temporal cortex impaired postoperative new learning, but the retrieval of problems overtrained preoperatively was relatively preserved. Subjects with perirhinal cortex ablation were severely impaired in new learning and at the retrieval of scene problems, but retention of object-reward associations was relatively well preserved. The results support the hypothesis that isolation of the inferior temporal cortex from basal forebrain and midbrain afferents results in dense anterograde amnesia, whereas the role of the perirhinal cortex in learning is dependent on the perceptual difficulty of the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned suppression of medial forebrain bundle and septal intracranial self-stimulation in the rat: Evidence for a fear-relief mechanism of the septum.

In 3 experiments, a conditioned emotional response (CER) paradigm was presented to 2 groups of male albino Sprague-Dawley rats (N?=?20) during intracranial self-stimulation (ICSS). One group barpressed for medial forebrain bundle (MFB) stimulation reward; the other group barpressed for septal stimulation reward. The MFB ICSS was found to be suppressed by the CER procedure, but this procedure failed to suppress septal ICSS. The difference between the 2 sites was found only when both MFB and septal ICSS current intensities were available at their optimal levels. When ICSS current intensities were lowered to either threshold or medium level, both groups exhibited the CER suppression effect. Ss were also tested for a possible analgesic effect produced by the ICSS. MFB stimulation was found to produce some degree of analgesia, but septal stimulation failed to produce any analgesic effect. Thus, the possibility that the attenuation of the CER suppression effect in the septal group was due to analgesia was excluded. The difference in MFB and septal ICSS behavior during the presentation of the aversive stimulus suggests a possible qualitative distinction between the reward functions of the 2 sites, and a possible fear-reduction property of the septal area. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Seizure activity and lesions of neuronal cells by intrahippocampal injection of guanidinosuccinic acid in rats]

Intrahippocampal injection(ihci) of guanidinosuccinic acid (GSA) to rats, induced typical generarized clonic seizures and epileptiform discharges in electrohippocampogram (EHG) and electrocorticogram (ECoG), degenerative changes of neuronal cells in the injected side hippocampus. The pyramidal cells in CA1 area were found to be more vulnerable to GSA than the granular cells. Phenobarbital and phenytoin are typical antiepiletics, but in no case did they successfully protect against GSA induced convulsions, epileptiform discharges in the EHG and ECoG and neurolysis. Ketamine, a selective noncompetitive NMDA receptor antagonist, was shown to protect against not only seizures, but also neuronal cell damage induced by GSA. All these results indicate that GSA very like the endogenous excitatory amino acid, glutamic acid, it also has such effects mentioned above. Therefore, the NMDA receptor may mediate both effects of GSA.     

The effect of L-DOPA on the motor activity of mouse fetuses

Most patients with acute myocardial infarction do not receive or are ineligible for thrombolytic therapy, and thus their prognosis is worse than that of the populations studied in the major, randomized, lytic therapy trials. We need to devise a cost-effective strategy with which to appropriately stratify these patients. Simple, easily ascertained clinical variables that are evident soon after hospital admission can identify higher-risk patients, who are likely to be older and less able to adequately complete an exercise test. In some patients, nuclear imaging tests are appropriate; low-dose dobutamine echocardiography and ambulatory ECG monitoring may also have a role. Greater use of routine cardiac catheterization (with assessment of ventricular function) might be the most appropriate way to stratify patients because it may overcome some of the limitations of noninvasive testing, will clearly define high-risk patients, and may facilitate early discharge from the hospital. Left ventricular function and the patency of the infarct-related artery will be determined, and patients with left main coronary disease, significant three-vessel coronary artery disease, and two-vessel coronary disease (especially with proximal left anterior descending coronary artery involvement) will be identified. An aggressive strategy of revascularization to improve survival in appropriate patients may be employed. Greater use of routine coronary arteriography after acute myocardial infarction would inevitably lower the threshold for inappropriate, potentially risky, and expensive further interventions. We need to focus our attention on the most appropriate strategies for the management of patients whose prognosis is worse than the prognosis of those who receive lytic therapy after acute myocardial infarction.     

The effect of post-training hypothalamic self-stimulation on sensory preconditioning in rats.

58 male hooded water-deprived rats experienced a preconditioning session (consisting of paired or unpaired presentations of a tone and a light) followed by either no self-stimulation, immediate self-stimulation, or self-stimulation delayed by 2 or 4 hrs. On the next 2 days, Ss experienced the conditioning phase in which the light was paired with a footshock. 24 hrs after the last conditioning trial, the transfer of the conditioned emotional response from the light to the tone was evaluated using a suppression-of-drinking procedure. Self-stimulation facilitated retention of the association between the tone and the light when it occurred within 2 hrs after preconditioning training, but not when it occurred 4 hrs after training. Immediate posttraining self-stimulation had no effect on Ss that experienced unpaired tone and light presentations during preconditioning training. Data suggest that the self-stimulation treatment strengthened the association between the tone and the light retroactively and noncontingently, and show that direct activation of the neural substrate of reinforcement can improve memory for associations formed between 2 neutral stimuli. (French abstract) (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions in the medial pallium on instrumental learning in the toad (Bufo arenarum)

Lesions of the medial pallium in toads significantly retarded extinction of a water-reinforced instrumental response in a runway training situation, relative to sham-operated and intact controls. The lesion had no effect on acquisition or in the amount of water uptake during acquisition. The results suggest that the medial pallium of toads plays a role in response inhibition. This possibility is discussed in relation to the results of analogous experiments with hippocampectomized rats.     

Effects of medial prefrontal or anterior cingulate cortex lesions on responding for cocaine under fixed-ratio and second-order schedules of reinforcement in rats

Four experiments examined the effects of excitotoxic, axon-sparing lesions of the medial prefrontal cortex or anterior cingulate cortex in rats on responding under different schedules of intravenous cocaine self-administration and on the locomotor stimulant effects of cocaine. Experiment 1 tested the acquisition and maintenance of cocaine self-administration under a fixed ratio schedule. Rats with medial prefrontal cortex lesions showed facilitated acquisition and enhanced responding for low doses of the drug when lesions were induced before self-administration behaviour was established. Lesions of the anterior cingulate cortex did not affect cocaine self-administration. In experiment 2, rats were trained to respond under a second-order schedule of cocaine reinforcement, where responding during the fixed interval was reinforced by presentation of a cocaine-associated visual stimulus under fixed-ratio contingencies. In control rats, these schedule conditions were found to maintain high rates of responding and a scalloped pattern of responding over time. Omission of conditioned stimulus presentation during the fixed interval significantly disrupted response patterns, confirming that the stimulus served to maintain responding during the fixed interval. By contrast, rats with medial prefrontal cortex lesions showed higher rates and disrupted patterns of responding that were unchanged by stimulus omission. Rats with lesions of the anterior cingulate cortex responded at high rates throughout the fixed interval under all test conditions, indicating that the cocaine-associated stimulus did not serve to maintain temporal patterns of responding in these rats. Experiment 3 demonstrated the lack of effect of either lesion on the acquisition of responding for a non-drug reinforcer, sucrose. In experiment 4, measures of spontaneous and cocaine-induced locomotor activity revealed that rats in both lesion groups were significantly more active than controls regardless of test conditions. These data indicate that facilitated acquisition of cocaine self-administration and disrupted response patterns under second-order schedule contingencies may result from deficits in behavioural inhibition induced by medial prefrontal cortical lesions that contrast with deficits following damage to other limbic cortical regions, such as the basolateral amygdala or anterior cingulate cortex.     

Intraoperative electroneurodiagnostics (transcranial electrical motor evoked potentials) to evaluate the functional status of anterior spinal roots and spinal nerves during brachial plexus surgery

Intradural spinal root lesions cannot be recognized by dissecting the brachial plexus and lead to ineffective surgery if they remain undetected. Therefore, patients need to undergo a diagnostic procedure to assess the intradural status of the spinal roots. Although motor recovery is the main goal of brachial plexus surgery, the techniques currently applied do not permit adequate evaluation of the anterior root. In search of an alternative, we performed intraoperative motor evoked potentials. Ninety spinal nerves in 19 patients suffering from brachial plexus lesions were dissected. Twenty-seven spinal nerves were avulsed; 8 nerves were disrupted and 17 were completely scarred, resulting in 25 stumps. Thirty-eight nerves appeared to be undamaged. On central stimulation, nerve compound action potentials were recorded from the exposed spinal nerves. Nerve compound action potentials could only be recorded from 21 stumps and from 32 apparently undamaged nerves. No recordings were obtained from 4 stumps and 7 spinal nerves in continuity. According to these findings, it is highly probable that surgery would have been insufficient in 10 spinal nerves if intraoperative motor evoked potentials had not been performed. We conclude that (1) intraoperative motor evoked potentials are an effective means for investigating the functional status of anterior motor roots and motor fibers in exposed spinal nerves, and (2) the use of motor evoked potentials should be considered during brachial plexus surgery to improve interventions.     

The enhancement of chlorpromazine-induced hypothermia by lesions in the anterior hypothalamus

1 Administration of chlorpromazine (Cpz), either systemically or centrally, to unanaesthetized rats at an environmental temperature of 23 degrees C caused dose-dependent hypothermia. 2 In order to achieve equivalent hypothermia, intraventricular administration required a total dose of 20 microgram Cpz and and intraperitoneal administration a dose of 9.7 mg/kg body weight. Accordingly, the dose-ratio between intraventricular and intraperitoneal administration was 1 to 110. Cpz apparently exerts its hypothermic effect by acting directly on central nervous structures rather than through peripheral sites. 3 Cpz-induced hypothermia was potentiated by preoptic anterior hypothalamic (POAH) lesions but not by lesions of the ventromedial nucleus (VMN) of the hypothalamus. It was found that Cpz induced hypothermia most readily in rats with large POAH lesions (-10.4 degrees C), less so in rats with spinal lesions (-5.5 degrees C) at least with control rats (-2.9 degrees C).     

Daily zinc supplementation effect on zinc deficiency in rats during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of 47 mg zinc supplementation on deficiency of zinc in rats during 98 d of restriction of motor activity (hypokinesia), which appeared by higher plasma zinc concentration. One Hundred 13-week-old Sprague-Dawley male rats weighing 360-390 g were used to perform the studies: They were equally divided into four groups: 1. Unsupplemented control animals (UCA); 2. Unsupplemented hypokinetic animals (UHA); 3. Supplemented control animals (SCA); and 4. Supplemented hypokinetic animals (SHA). For the simulation of the effect of hypokinesia (HK), the UHA and SHA were kept in small individual cages made of wood, which restricted their movements in all directions without hindering food and water intake. The SCA and SHA received daily with their food an additional amount of zinc. Before and during the experimental period of 98 d, plasma, urinary and fecal zinc, balance of zinc, food intake, and body weight were determined at different intervals. In the SHA and UHA, the concentration of zinc in plasma, and the elimination of zinc in urine and feces increased significantly when compared with the SCA and UCA, whereas the balance of zinc was negative. The body weight and food intake decreased significantly in the SHA and UHA when compared with the SCA and UCA. The increased plasma concentration of zinc in both the SHA and UHA groups was in contrast to the observed hypozincnemia during prolonged immobilization as during prolonged hospitalization. This reaction suggests that there may be some other mechanisms that are affecting the process of control and regulation of zinc metabolism during prolonged HK. It was concluded that exposure to prolonged restriction of motor activity of rats induces significant increases in plasma concentration, fecal and urinary elimination of zinc in the presence of negative zinc balance and regardless the daily intake of large amounts of zinc with their food, leading to zinc deficiency.     

Daily magnesium supplementation effect on magnesium deficiency in rats during prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of magnesium (Mg) supplements in rats during prolonged restriction of motor activity (hypokinesia [HK]) and in the presence of Mg deficiency, which is characterized by increased rather than decreased plasma Mg concentration, as occurs in ambulatory conditions. The studies were performed during 98 days of HK on 100 13-week-old Sprague-Dawlay male rats weighing 360 to 390 g. They were equally divided into four groups: (1) unsupplemented control animals (UCA), (2) unsupplemented hypokinetic animals (UHA), (3) supplemented control animals (SCA), and (4) supplemented hypokinetic animals (SHA). For the simulation of the hypokinetic effect, SHA and UHA were kept for 98 days in small individual wood cages that restricted their movements in all directions without hindering food and water intake. The SCA and SHA took daily with their food an additional 0.35 mg of Mg. Before and during the hypokinetic period of 98 days, Mg in plasma, urine, and feces, balance of Mg, food intake of Mg, and body weight were determined at different intervals. In SHA and UHA, plasma Mg concentration and excretion of Mg in urine and feces increased significantly compared with SCA and UCA. Magnesium balance was negative in UHA and AHA throughout the hypokinetic period. Body weight and a food intake decreased significantly in SHA and UHA when compared with SCA and UCA. Significant losses of Mg in SHA and UHA occurred in the presence of Mg deficiency and suggest that prolonged HK induces another factor that influences Mg metabolism. We conclude that prolonged HK causes significant changes in Mg values of plasma, urine, and feces and a negative Mg balance in rats, despite Mg supplements leading to Mg deficiency.     

The effect of vitamin E on antioxidant tissue activity in pregnant rats with streptozocin-induced diabetes]

When home enteral nutrition is needed, there is still, despite the undisputed increase in the quality of life that can be achieved with a Percutaneous Endoscopic Gastrostomy (PEG), a reservation in its use because this technique and its maintenance is considered to be very costly. We aim to assess the true cost of home enteral nutrition using the oral route, a nasogastric tube, and PEG. PATIENTS AND METHODS: The data of 65 patients who required home enteral nutrition during 1996, were analyzed retrospectively. The access route was a nasogastric tube in 20 cases, 18 patients had PEG, and 27 candidates used an oral route. The average age was 56 years. 50% were men and 50% were women. The most common diagnoses that led to the indication were oropharyngeal-maxillofacial neoplasms and neurological disorders. In all cases the material and formula used was assessed, as were the associated complications and the cost of the at home enteral nutrition. RESULTS: The average duration of the treatment was 175 +/- 128 days, and this was similar in all three groups. The average formula/day cost was slightly higher in the patients using the oral access route. The average total day cost and the average material/day cost was slightly higher in patients with a PEG. Patients with a PEG presented fewer complications than those with a nasogastric tube. The cost derived from possible complications must be higher in the nasogastric tube group, especially considering the repeated tube changes due to obstruction or loss. CONCLUSIONS: The cost of home enteral nutrition is slightly lower if one uses a nasogastric tube. The greater incidence of complications that were mild but required a tube change, in this case a nasogastric tube, suggests higher indirect costs. The oral route is associated with the need for special formulae that are more expensive.     

Electrolytic lesions of the nucleus accumbens core (but not the medial shell) and the basolateral amygdala enhance context-specific locomotor sensitization to nicotine in rats.

We previously demonstrated that lesions of the nucleus accumbens (NAc) core enhanced locomotion and locomotor sensitization to repeated injections of nicotine in rats (Kelsey & Willmore, 2006). In this study, we compared the effects of separate lesions of the NAc core, NAc medial shell, and basolateral amygdala on context-specific locomotor sensitization to repeated injections of 0.4 mg/kg nicotine. Electrolytic lesions of the NAc core increased locomotion, and lesions of the core (but not the shell) and the basolateral amygdala enhanced context-specific locomotor sensitization by enhancing the development of sensitization in paired rats and decreasing expression in unpaired rats relative to sham-operated rats when challenged with an injection of 0.4 mg/kg nicotine in the locomotor chambers. These data are consistent with findings that the NAc core and the basolateral amygdala share a variety of behavioral functions and anatomical connections. The findings that lesions of these structures enhance context-specific locomotor sensitization while typically impairing other reward-related behaviors also indicate that the processes underlying locomotor sensitization and reward are not identical. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Combined effects of various forms of motor deprivation and gamma irradiation on the higher nervous activity in rats]

Effects of gamma-radiation at a dose of 3 Gy against either antiorthostatic hypodynamia (AOH) or hypokinesia (HK) on formation of the differentiated motor-drinking reflex (DR) were compared. Each of the forms of motor deprivation hindered the elaboration of DR; gamma-irradiation aggravated these disorders. At the same time, AOH led to significantly more severe disturbances in the higher nervous activity including the generalized excitation, pathologic aggressiveness and neurotization of animals. In contrast, hypokinesia stimulated the active elements of behavior which inhibit the passive-defensive behavior and a fear reaction. Therefore, the modifying effect of irradiation becomes apparent only if combined with AOH.