Instanton Equations for the Supersymmetric CP^{N-1} Sigma Model on Non(anti)commutative Superspace

We study the instanton equation of the supersymmetric CP^{N-1} sigma model on non(anti)commutative superspace in two dimensions. We show that the undeformed instanton equation is consistent with the deformed equations of motion. Then we conclude that the instanton equation is not deformed by superspace non(anti)commutativity.Comment: 6 page

Differential Effects of Psychological and Physical Stress on the Sleep Pattern in Rats

In the present study, we investigated the acute effects of 2 different kinds of stress, namely physical stress (foot shock) and psychological stress (non-foot shock) induced by the communication box method, on the sleep patterns of rats. The sleep patterns were recorded for 6 h immediately after 1 h of stress. Physical and psychological stress had almost opposite effects on the sleep patterns: In the physical stress group, hourly total rapid eye movement (REM) sleep and total non-REM sleep were significantly inhibited, whereas psychological stress enhanced hourly total REM sleep but not total non-REM sleep. Further results showed that total REM sleep, total non-REM sleep, total sleep and the total number of REM sleep episodes in 5 h were reduced, and that sleep latency was prolonged compared to the control group. On the other hand, in the psychological stress group, the total REM sleep in 5 h was increased significantly due to the prolongation of the average duration of REM sleep episodes and reduced REM sleep latency. In addition, the plasma of corticosterone increased significantly after physical stress but not after psychological stress. These results suggested that the sleep patterns, particularly the patterns of REM sleep following physical and psychological stress, are probably regulated by 2 different pathways.</p

Influence of imipramine on the duration of immobility in chronic forced-swim-stressed rats.

We studied the influence of imipramine on the duration of immobility in chronic forced-swim-stressed rats. Both single and chronic administration of imipramine potently shortened immobility in naive rats during forced-swim testing. However, chronic, 14-day forced-swim stress testing blocked the immobility-decreasing effect induced by a single administration of imipramine. When imipramine was administered for 14 days concurrently with forced-swim stress testing, immobility was shortened significantly. From the viewpoint of imipramine's effect, these findings suggest that chronic forced-swim stress testing in rats may be an effective animal model for depression.</p

Motivational Effects of Nicotine as Measured by the Runway Method Using Priming Stimulation of Intracranial Self-stimulation Behavior

It is well known that priming stimulation promotes the motivational effects of intracranial self-stimulation(ICSS) behavior. An experimental methodology using the runway method could separately study the reward and motivational effects of ICSS behavior. In the present study, we examined the motivational effect of nicotine as measured by the runway method using priming stimulation of ICSS behavior. Electrodes were implanted chronically into the medial forebrain bundle (MFB) in rats. A lever for stimulation of the MFB was set on the opposite side of the start box in the apparatus, and rats were trained to get a reward stimulation (50-200 microA, 0.2 ms, 60 Hz) of MFB when the goal lever was pressed. After the rats were trained to press the lever, a priming stimulation of the MFB was performed. After receiving the priming stimulation, rats were placed at the start box of the runway apparatus, and the running time duration until the goal lever was pressed was measured. Subcutaneous injection of nicotine at a dose of 0.2mg/kg produced an increase in running speed to obtain the reward stimulation, and priming stimulation facilitated the motivational effect to obtain the electrical brain stimulation reward in the rats. These results suggest that nicotine significantly enhanced the motivational effect on ICSS behavior as determined using the runway method. The runway method using priming stimulation of ICSS behavior may become the new experimental methodology with which to measure the motivational effect of some drugs.</p

Effect of Brewer's Yeast-Induced Pyrexia on Aminophylline-Elicited Convulsions in Mice

Theophylline-associated convulsions have been observed most frequently in children with fever, but the mechanism is not fully understood. In this study, we investigated the basic mechanism of aminophylline [theophylline-2-ethylenediamine]-induced convulsions and the effects of Brewer's yeast-induced pyrexia in mice. Diazepam (5-10mg/kg, i.p.), a benzodiazepine receptor agonist, significantly prolonged the onset and significantly decreased the incidence of convulsions induced by aminophylline (350mg/kg, i.p.). However, the gamma aminobutyric acid (GABA)A receptor agonist muscimol (1-4mg/kg, i.p.), the GABAB receptor agonist baclofen (2-4mg/kg, i.p.) and the N-methyl-D-aspartic acid receptor antagonist dizocilpine (0.1-0.3mg/kg, i.p.) failed to protect against the convulsions. 20% Brewer's yeast (0.02ml/g, s.c.) increased body temperature by 1.03, and also significantly shortened the onset and significantly increased the incidence of convulsions induced by aminophylline. The anticonvulsant action of diazepam (2.5-10mg/kg, i.p.) on the convulsions induced by aminophylline was reduced by Brewer's yeast-induced pyrexia. The proconvulsant actions of the GABAA receptor antagonists picrotoxin (3-4mg/kg, i.p.) and pentylenetetrazol (40-60mg/kg, i.p.) were enhanced by Brewer's yeast. These results suggest that the anticonvulsant action of diazepam against aminophylline is reduced by Brewer's yeast-induced pyrexia, and that GABAA receptors are involved in the aggravation of the convulsions by Brewer's yeast in mice.</p

The Influence of Hyperactivity of the Hypothalamic-pituitary-adrenal Axis and Hyperglycemia on the 5-HT2A Receptor-mediated Wet-dog Shake Responses in Rats

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis induces hyperglycemia and serotonin (5-HT)2A receptor supersensitivity. In the present study, to investigate the effect of hyperglycemia on the function of 5-HT2A receptors, we compared the 5-HT2A receptor-mediated wet-dog shake responses in rats treated with adrenocorticotropic hormone (ACTH), dexamethasone and streptozotocin. ACTH (100 &#956;g/rat per day, s.c.), dexamethasone (1 mg/kg per day, s.c.) and streptozotocin (60 mg/kg, i.p.) produced significant hyperglycemia at 14 days after the start of these treatments, and the hyperglycemia was most pronounced in the streptozotocin-treated rats. The wet-dog shake responses induced by (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT2A receptor agonist, were significantly enhanced at 14 days after repeated treatment with ACTH and dexamethasone. However, streptozotocin-induced diabetes had no effect on the wet-dog shake responses. The results of the present study suggest that hyperglycemia is not strongly associated with the enhanced susceptibility of 5-HT2A receptors under the condition of hyperactivity of the HPA axis.</p

Inhibitory Effects of Valproate on Impairment of Y-maze Alternation Behavior Induced by Repeated Electroconvulsive Seizures and c-Fos Protein Levels in Rat Brains

We previously showed that inhibition of repeated electroconvulsive shock (ECS)-induced seizures through 7-day administration of anti-epileptic drugs suppressed the impairment of spontaneous alternation behavior in the Y-maze test in rats. To clarify the precise mechanism(s), we investigated the effect of valproate on such impairment and examined the levels of brain-derived neurotrophic factor (BDNF) and c-Fos protein in the prefrontal cortex and the hippocampus 24h after the last administration of ECS. Seven-day intraperitoneal (i.p.) administration of valproate (400mg/kg) suppressed the impairment of spontaneous alternation behavior. Repeated ECS increased the BDNF protein levels in the hippocampus and prefrontal cortex in the presence or absence of valproate, indicating that the increase in BDNF protein levels resulted from electrical stimulation. c-Fos protein levels were significantly decreased in the hippocampal dentate gyrus after repeated ECS, but valproate had no significant effect on decreased c-Fos protein levels. Valproate＋ECS significantly increased the c-Fos protein levels of the prefrontal cortex compared with the ECS group. These findings suggest that the inhibitory effect of valproate on repeated ECS-induced impairment of spontaneous alternation behavior may be linked to the prefrontal cortex

Effects of anxiolytic drugs on rewarding and aversive behaviors induced by intracranial stimulation.

In considering the characteristics of the action of anxiolytic drugs and their mechanism in the brain, it may be necessary not only to study the behavioral pharmacology but also to perform brain site research. In the present study, the action of anxiolytic drugs was examined with respect to various behaviors that were induced by stimulating the brain areas related to emotions such as reward (pleasure) or aversion in rats. First, the low rate of response in lateral hypothalamic self-stimulation behavior was induced by schedules of low current brain stimulation, variable interval (VI) and differential reinforcement of low rate (DRL). Anxiolytic drugs such as benzodiazepines facilitated these low-rate responses. The drug susceptibility was highest in the low current stimulation, lower in the VI stimulation, and lowest in the DRL stimulation schedules. Furthermore, it was found by the auto-titration method in intracranial self-stimulation behavior that anxiolytic drugs decreased the threshold of stimulation reward. Second, it was recognized using the decremental lever pressing (DLP) paradigm that anxiolytic drugs increased the threshold of aversive stimulation of mesencephalic dorsal central gray (DCG), and this increasing effect of the drug was antagonized by GABA receptor blockers such as biccuculline. Finally, it was examined whether or not the conflict situation is established by combining brain stimulation reward and aversion, such as foot-shock or DCG stimulation. As a result, the conflict behavior was established by combining not only the brain stimulation reward and foot-shock aversion, but also the brain stimulation reward and DCG stimulation aversion. Further anxiolytic drugs exhibited anti-conflict action in both situations. The susceptibility of anxiolytic drugs was higher with respect to the conflict behavior induced by intracranial reward and aversion than to that induced by the conventional method based on milk reward and foot-shock aversion. These results suggest that behavioral methods using brain stimulation can examine the mechanisms of direct drug action at the brain stimulation site. Indeed, in the present brain stimulation behavioral study, anxiolytic drugs such as benzodiazepines increased the stimulation threshold in lateral hypothalamic self-stimulation and inhibited the DCG aversive stimulation, thus resulting in an anticonflict action of the drugs.</p