Effects of d- versus l-amphetamine, food deprivation, and current intensity on self-stimulation of the lateral hypothalamus, substantia nigra, & medial frontal cortex of the rat.

Studied intracranial self-stimulation (ICSS) in 18 adult Sprague-Dawley rats with chronically implanted lateral hypothalamic, substantia nigra, or medial frontal cortex bipolar electrodes. A comparison of the effects of dextro- and levoamphetamine on ICSS response rate indicated that the dextro isomer had a greater facilitatory effect than the levo isomer at lateral hypothalamic and substantia nigra electrode sites but that neither isomer significantly affected medial frontal cortex ICSS. Dextroamphetamine resulted in a dose-related increase in motor activity, but the same doses of the levo isomer resulted in decreased motor activity. Only lateral hypothalamic ICSS response rates increased significantly in response to food deprivation. Increases in current intensity above the level used for amphetamine and food-deprivation testing facilitated lateral hypothalamic and substantia nigra ICSS response rates. The responsiveness of ICSS at each electrode site appeared to be correlated with the fiber- and cell-body densities of catecholaminergic systems in the brain. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dopaminergic and serotoninergic components of the self-stimulation reaction of the lateral hypothalamus in rats with disruption of the medial prefrontal cortex

The hospital in the future will be faced with the major problem of managing and optimizing the use of images provided from numerous sources examining both anatomy (MRI, CT-scan...) and function (gamma-camera, PET-scan...). One of the first to benefit from such rationalization will be the surgeon. After studying the results of the physical examination, the laboratory reports and the medical imaging, the surgeon will decide on the best curative measured and the best surgical route before operating. He thus needs a computer to assist him in integrating the multi-modal information available for his patient, in particular the imaging with automatic integration and visualisation in synoptic mode (perception step), showing the trajectory of possible access routes to the target organ, memorization of the chosen route (decision step) and real operation either using laser or a manuel tool, or with robot assistance under human control (action step). This close cooperation between surgery and computers is called computer-assisted surgery. A few examples of current uses an future perspectives of this new field of surgery are presented.     

Self-stimulation thresholds and dorso-ventral variation in the lateral hypothalamus in mouse: effects of food and water deprivation

During the thermal decomposition of cysteine, cystine, N-acetylcysteine, 4-thiazolidinecarboxylic acid, cysteine methyl ester, in soy bean oil at 200 degrees C, a series of compounds containing sulphur are formed. Besides 15 alkylthiazoles, -thiazolines and -thiazolidines, compounds with 2 and 3 S-atoms can also be identified: ethane-1,2-dithiole, diethyldisulfide, diethyltrisulfide, 2-methyl-1,3-dithiolane, 1,2-dithiane, thialdine, 1,2,4-trithiolanes, 1,2,4-trithianes and 2-methyl-thiazolidino-(3,4-b-)-thiazolidine. N,N'-dibutyrylcystamine shows an antioxidant effect.     

Changes in self-stimulation at stimulation-bound eating and drinking sites in the lateral hypothalamus during food or water deprivation, glucoprivation, and intracellular or extracellular dehydration.

Examined the effects of hunger induced by food deprivation, 2-deoxy-{d}-glucose (200 mg/kg), or insulin (2 U/kg) and thirst induced by water deprivation, sodium chloride (4 M), or polyethylene glycol (5 ml of 30% w/w) on lateral hypothalamic self-stimulation in 40 male Long-Evans rats. Changes in self-stimulation were evaluated at electrodes that produced stimulation-bound eating and/or drinking or neither behavior. Daily 30-min test sessions consisted of 3 5-min periods of self-stimulation alternated with 3 5-min periods when barpresses resulted in 5-sec time-out from experimenter-delivered stimulation (stimulation escape). Food deprivation significantly increased self-stimulation; insulin, 2-deoxy-{d}-glucose, and sodium chloride significantly suppressed self-stimulation; water deprivation mildly inhibited self-stimulation; and polyethylene glycol had no effect. This pattern of findings was noted at electrodes that did and those that did not elicit eating and/or drinking. Findings do not support the hypothesis that the magnitude of lateral hypothalamic self-stimulation is differentially and predictably controlled by specific drive mechanisms indexed by the consummatory behaviors also elicited by the stimulation. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competition between lateral hypothalamus and ventromedial tegmentum in electrical self-stimulation in the rat.

Used 14 male Sprague-Dawley rats with 2 bipolar electrodes, one in the lateral hypothalamus (LH) and the other in the ventromedial tegmentum (VMT). After training, barpressing rates for LH and VMT self-stimulation were studied separately by switching the stimulation alternately to LH and to VMT (single-bar test), or were studied in a choice test where Ss had to choose between LH and VMT stimulation by pressing 2 independent bars. In the single-bar test when threshold currents were used, Ss self-stimulated significantly more in LH than in VMT, but the reverse was observed at high current intensities. Some negative behaviors observed in LH with strong currents did not generalize when stimulation was switched to the VMT probe, suggesting a relative independence between LH and VMT. The comparison between the relative preference of Ss for LH or VMT stimulation in the choice test and the barpressing rates in the single-bar test shows that in this last test barpressing rates reflect the rewarding value of stimulation only when weak current intensities are used. (French summary) (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeding and drinking pathways between medial and lateral hypothalamus in the rat.

Carried out 3 experiments, using 101 female rats of the CFE strain. Bilateral parasagittal transections were made at different lateral and dorsal-ventral positions in and between the ventromedial hypothalamus (VMH) and lateral hypothalamus (LH). Cuts through or just lateral to the VMH produced hyperphagia and obesity, while cuts through or medial to the LH produced, depending upon their exact position and the diet, either temporary aphagia-hypophagia, mild hyperphagia, or no effect. The cuts medial to the LH, but not the others, abolished insulin-induced eating. All cuts produced deficits in drinking regulation that varied according to their exact position. These deficits included hypodipsia, mild hyperdipsia, and reduced water/food ratios, as well as reduced drinking responses to food deprivation, water deprivation, hypertonic sodium chloride injections, and polyethylene glycol injections. The knife cuts also produced changes in gustatory reactivity. The hypothalamic pathways responsible for these effects are discussed. (54 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Possible regeneration of rat medial frontal cortex following neonatal frontal lesions

The experiments described here show that the cavity left by midline frontal cortex removals at 10 days of age (P10) fills in with neural tissue. Similar changes are not found at earlier and later ages. This neuronal filling is blocked by prior pretreatment by administration of Bromodeoxyuridine (BrdU) on embryonic day 13. Administration of BrdU following the P10 lesion does not interfere with regrowth. Subsequent immunohistochemical staining for BrdU demonstrates the regrown area to be composed of newly generated cells. which include pyramidal and nonpyramidal neurons. Injections of a retrograde tracer into the striatum or posterior parietal cortex shows that the new neurons have connections similar to those of undamaged brains. The regrowth of this tissue is correlated with recovery of function in a test of forelimb use. Thus, the mammalian brain, during some privileged postnatal stages of growth. is capable of extensive reorganization that includes regeneration of lost neurons. These results are discussed in relation to the proximity of the lesion to the stem cells in the lateral ventricle and their postnatal migrational activities.     

Time-dependent changes in amphetamine self-administration following frontal cortex ablations in rats.

Conducted 2 experiments with a total of 28 operated, 25 sham-operated, and 21 normal female Sprague-Dawley albino rats. Ss were trained to intravenously self-administer dextroamphetamine (.01 mg/kg per reward infusion) during daily 1-hr testing sessions. Following removal of frontal cortex, rates of dextroamphetamine self-administration were higher at early (3-5 days) postoperative intervals but lower at later (2-4 wks) postoperative intervals. These and other results indicate that, as a function of time after surgery, frontal Ss were first hyposensitive and then became increasingly hypersensitive to the rewarding effect of dextroamphetamine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal activity, behavior, self-stimulation, and heart rate during electrical stimulation of the lateral hypothalamus.

Observed hippocampal electrical activity in relation to behavior elicited by stimulation of the lateral hypothalamus in 30 male hooded rats. Rhythmical slow activity (RSA) was always present during walking, rearing, digging, bar pressing, and other presumably "voluntary" movements, but at low stimulation intensities it was often absent during licking, chewing, face washing, and other presumably "automatic" movements. At higher stimulation intensities, Ss became hyperactive and RSA was almost continually present. No relation was found between RSA and heart rate or licking movements. An ascending hypothalamic system may require hippocampal participation in the control of voluntary movements, but hippocampal participation may not be required for the control of more automatic movements. (30 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Afferent connections of the medial frontal cortex of the rat. II. Cortical and subcortical afferents

In order to compare the frontal cortex of rat and macaque monkey, cortical and subcortical afferents to subdivisions of the medial frontal cortex (MFC) in the rat were analyzed with fluorescent retrograde tracers. In addition to afferent inputs common to the whole MFC, each subdivision of the MFC has a specific pattern of afferent connections. The dorsally situated precentral medial area (PrCm) was the only area to receive inputs from the somatosensory cortex. The specific pattern of afferents common to the ventrally situated prelimbic (PL) and infralimbic (IL) areas included projections from the agranular insular cortex, the entorhinal and piriform cortices, the CA1-CA2 fields of the hippocampus, the subiculum, the endopiriform nucleus, the amygdalopiriform transition, the amygdalohippocampal area, the lateral tegmentum, and the parabrachial nucleus. In all these structures, the number of retrogradely labeled cells was larger when the injection site was located in area IL. The dorsal part of the anterior cingulate area (ACd) seemed to be connectionally intermediate between the adjacent areas PrCm and PL; it receives neither the somatosensory inputs characteristic of area PrCm nor the afferents characteristic of areas PL and IL, with the exception of the afferents from the caudal part of the retrosplenial cortex. A comparison of the pattern of afferent and efferent connections of the rat MFC with the pattern of macaque prefrontal cortex suggests that PrCm and ACd areas share some properties with the macaque premotor cortex, whereas PL and IL areas may have characteristics in common with the cingulate or with medial areas 24, 25, and 32 and with orbital areas 12, 13, and 14 of macaques.     

Differential role of the medial and lateral prefrontal cortices in fear and anxiety.

In the rat, both the medial and lateral prefrontal. cortices (PFC; mPFC and lPFC, respectively) have direct connections with limbic structures that are important in the expression of fear and anxiety. The present study investigated the behavioral effects of excitotoxic lesions of either the mPFC or the lPFC on conditioned and unconditioned fear paradigms. In both unconditioned fear paradigms (open field, elevated plus-maze), lesions of the mPFC decreased anxiety. In fear conditioning, lPFC lesions substantially increased freezing throughout the different phases of the experiment, whereas mPFC lesions increased freezing to contextual cues and showed reduced freezing to discrete cues. These results support the functional role of the PFC in mediating or modulating central states of fear and anxiety and suggest a functional dissociation between the lPFC and mPFC in their role in fear and anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Residual effects of food deprivation on food consumption and runway performance in the satiated rat.

2 experiments studied the residual effects of prior food deprivation in 35 female and 28 male Holtzman rats as measured by probability to eat and acquisition of a running response under satiated conditions. Although the effects were positively related to the severity of prior deprivation (Exp II), a drive-conditioning interpretation was questioned because of 3 findings: (a) effects were not dependent on exposure to the test situation when Ss were deprived (Exp I and II); (b) prolonged testing during satiation increased rather than decreased the effects (Exp I and II); and (c) the instrumental response decreased only when reward was withheld (Exp I). (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the frontal cortex in the mouse in behavioral sensitization to amphetamine

Symptom production in groundnut plants infected with groundnut rosette virus (GRV) depends on the presence of satellite RNA (sat-RNA) in the GRV culture, and sat-RNA variants that induce only mild symptoms are known. One such variant drastically diminished the replication of GRV genomic RNA in infected Nicotiana benthamiana plants. This down-regulating ability did not involve either of the two open reading frames in the sat-RNA but was controlled by a region near its 5' end, which is required for sat-RNA replication. When N. benthamiana plants were inoculated with GRV and the mild satellite and challenged by inoculation with a GRV isolate (YB) containing a sat-RNA that induces yellow blotch symptoms, no symptoms appeared and little GRV genomic RNA or sat-RNA was detected in the plants, provided the two inoculations were no more than 2 days apart. A GRV isolate containing a sat-RNA that neither induces symptoms in N. benthamiana nor affects genomic RNA accumulation also provided protection against yellow blotch symptom production if inoculated before or up to 2 days after isolate YB. However, in this case protection ws incomplete and both GRV RNA and sat-RNA accumulated to normal levels. It is suggested that sequences from the mild sat-RNA may provide a novel source of resistance against rosette disease.     

Flavor and the frontal cortex.

Rats were trained to discriminate an aqueous compound of an odor and taste (amyl acetate and NaCl) from the components of the compound before removal of one olfactory bulb and the contralateral ventrolateral frontal cortex. In postoperative tests, experimental rats performed much more poorly than nonlesioned controls or controls which had all lesions made in the same hemisphere. However, there were no significant differences among groups on tests for detection of amyl acetate and NaCl. These results provide evidence that integration of taste and smell in the production of flavor occurs in the ventrolateral frontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovery of delayed alternation in rats after lesions in medial frontal cortex and septum.

Two experiments using contingently reinforced T-maze alternation with 48 male Long-Evans and hooded rats found that (a) normal Ss, after achieving high accuracy in alternation with brief (0 sec) intertrial intervals (ITIs), dropped to chance levels with longer ITIs (90 sec) but reacquired effective alternation with additional practice; (b) small lesions in mediodorsal pregenual cortex had no effect on postoperative retention of alternation at either short or long ITIs; (c) however, small lesions in posterodorsal septum temporarily disrupted alternation at brief ITIs, whereas at long ITIs Ss chose randomly and never recovered; and (d) large lesions in medial frontal cortex disrupted retention of alternation at brief ITIs of 10 sec but significant recovery did occur with additional experience. Implications regarding task difficulty and locus of lesion for recovery of function are discussed. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the effects of morphine, pentazocine, cyclazocine and amphetamine on intracranial self-stimulation in the rat

Rats were trained to press a lever in order to stimulate their hypothalamus through a chronically implanted electrode. Dose-response curves were determined for the effects of morphine (0.3-10 mg/kg), pentazocine (1.0-30 mg/kg), cyclazocine (0.03-30 mg/kg) and d-amphetamine (0.1-3.0 mg/kg) on responding for intracranial stimulation, and then were redetermined in the presence of one or two doses of naloxone. The three analgesics produced only dose-related decreases in responding with the following relative potencies: cyclazocine greater than morphine greater than pentazocine. The well-documented rate-increasing effects of d-amphetamine on intracranial self-stimulation were observed at 0.3 and 1.0 mg/kg of the drug; decreases in responding at 3.0 mg/kg were associated with stereotyped behavior. Naloxone, which had no effect of its own on self-stimulation, increased the dose of the analgesics required to depress response rate in a manner consistent with a competitive antagonism. In contrast, response rates at all doses of d-amphetamine tested in the presence of naloxone. Thus, the interaction between naloxone and d-amphetamine is qualitatively different from the one between naloxone and the analgesics. This finding extends to intracranial self-stimulation the generality of a previous report of interactions between d-amphetamine and naloxone on behavior in the rat.     

Neuronal activity in medial frontal cortex during learning of sequential procedures

To study the role of medial frontal cortex in learning and memory of sequential procedures, we examined neuronal activity of the presupplementary motor area (pre-SMA) and supplementary motor area (SMA) while monkeys (n = 2) performed a sequential button press task, "2 x 5 task." In this paradigm, 2 of 16 (4 x 4 matrix) light-emitting diode buttons (called "set") were illuminated simultaneously and the monkey had to press them in a predetermined order. A total of five sets (called "hyperset") was presented in a fixed order for completion of a trial. We examined the neuronal activity of each cell using two kinds of hypersets: new hypersets that the monkey experienced for the first time for which he had to find the correct orders of button presses by trial-and-error and learned hypersets that the monkey had learned with extensive practice (n = 16 and 10 for each monkey). To investigate whether cells in medial frontal cortex are involved in the acquisition of new sequences or execution of well-learned procedures, we examined three to five new hypersets and three to five learned hypersets for each cell. Among 345 task-related cells, we found 78 cells that were more active during performance of new hypersets than learned hypersets (new-preferring cells) and 18 cells that were more active for learned hypersets (learned-preferring cells). Among new-preferring cells, 33 cells showed a learning-dependent decrease of cell activity: their activity was highest at the beginning of learning and decreased as the animal acquired the correct response for each set with increasing reliability. In contrast, 11 learned-preferring cells showed a learning-dependent increase of neuronal activity. We found a difference in the anatomic distribution of new-preferring cells. The proportion of new-preferring cells was greater in the rostral part of the medial frontal cortex, corresponding to the pre-SMA, than the posterior part, the SMA. There was some trend that learned-preferring cells were more abundant in the SMA. These results suggest that the pre-SMA, rather than SMA, is more involved in the acquisition of new sequential procedures.     

Cognitive resources and dual-task interference effects at retrieval in normal people: The role of the frontal lobes and medial temporal cortex.

Conducted 3 experiments to examine the hypothesis that concurrent secondary tasks at retrieval will interfere more with long-term, episodic memory functions involving the frontal lobes than those involving the medial temporal lobes hippocampus (MTL/H). The rationale is that strategic retrieval processes mediated by the frontal lobes place greater demands on cognitive resources than do relatively automatic associative retrieval processes (ecphory) mediated by the temporal lobes. In Exps 1 and 2, sequential finger tapping was performed at encoding, at retrieval, at both, or at neither. Recall of a categorized list of 16 words from the California Verbal Learning Test in Exp 1, and release from proactive inhibition (PI) in Exp 2, both being tests that involve the frontal lobes, were impaired if normal Ss tapped at both encoding and retrieval. Concurrent tapping had little effect on rate of learning in Exp 1 and on total words recalled during the buildup of PI in Exp 2, both of which are indices that are affected more by MTL/H than by frontal lesions. In Exp 3, tapping by normal Ss affected letter fluency, a test more sensitive to frontal lobe than temporal lobe damage, but not category fluency, for which the reverse is true. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of dopamine in maintaining intracranial self-stimulation in the ventral tegmentum, nucleus accumbens, and medial prefrontal cortex.

Male albino Wistar rats were prepared with 2 chronic bipolar electrodes implanted ipsilaterally in the ventral tegmentum and either the nucleus accumbens or the medial prefrontal cortex. Once stable intracranial self-stimulation was elicited from both midbrain and forebrain electrodes, 6-hydroxydopamine lesions were placed into the ascending dopaminergic pathways between the rewarding electrode placements at the level of the lateral hypothalamus. Data suggest that dopamine plays an important role in self-stimulation in the ventral tegmentum and contributes to this behavior in the prefrontal cortex. Findings also show that nondopaminergic systems contribute to the phenomenon of brain-stimulation reward. (French summary) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)