Pharmacologically distinctive behaviors other than burying marbles during the marble burying test in mice

In the marble burying test, we focused on the 5 distinctive behavioral parameters of mice other than burying marbles, i.e. digging, latency to the first digging, exploration around marbles, rearing and locomotor activity. Typical anxiolytics or antidepressants with different mechanisms, fluvoxamine (30 mg/kg, selective serotonin reuptake inhibitor), bupropion (60 mg/kg, noradrenaline and dopamine reuptake inhibitor), imipramine (60 mg/kg, tricyclic antidepressant) and diazepam (10 mg/kg, benzodiazepine) were used to examine whether these behavioral parameters are sensitive to pharmacological treatments. Each of the drugs demonstrated an individual action pattern on the 4 behavioral parameters (latency to the first digging, exploration around marbles, rearing and locomotor activity). On the other hand, all 4 drugs reduced burying marbles and digging, which were correlated with each other. These results suggest that the former 4 behavioral parameters are sensitive to pharmacological treatment and that pharmacological regulation mechanisms of them may be different from burying marbles and digging. They could be useful to identify the type of action of a test drug like selective serotonin reuptake inhibitor, noradrenaline and dopamine reuptake inhibitor, tricyclic antidepressant or benzodiazepine.

Inhibition of Phosphodiesterase Type 4 Decreases Stress-Induced Defecation in Rats and Mice

BACKGROUND/AIMS

Phosphodiesterase type 4 (PDE4) has been previously shown to regulate colonic contractile activity in vitro. In this study, the effects of PDE4 inhibition were assessed in a model of stress-induced defecation previously demonstrated to be due to increased colonic transit/evacuation.

METHODS

Rats were individually placed in a mild restraint cage and placed into a 12 degrees C environment (cold-restraint stress) for 60 min. Mice received restraint (only) stress at room temperature for 30 min. Loperamide (positive control compound) or two different PDE4 inhibitors (rolipram and roflumilast) were administered orally at several doses to the rodents 1 h before stress began. Vehicle alone was administered for comparison. The number of fecal pellets expelled during stress (fecal pellet output), total fecal pellet wet weight and total fecal water content were measured.

RESULTS

Loperamide produced a dose-related decrease (ID(50)s in mg/kg) in fecal pellet output (rat = 7.4, mouse = 0.7) and significantly decreased fecal wet weight (72.9%) and decreased fecal percent water content (9.4%). The two PDE4 inhibitors produced a similar dose-related inhibition of fecal pellet output. Rolipram exhibited ID(50)s in rat and mouse of 14.1 and 27.1, respectively. Rolipram significantly decreased fecal wet weight (58.8%) but increased fecal percent water content (15.0%). For roflumilast, ID(50)s were 24.2 mg/kg and 12.4 in the rat and mouse, respectively. Although roflumilast also significantly (p < 0.05) decreased fecal wet weight (47.2%), it did not significantly increase fecal percent water content.

CONCLUSIONS

These data indicate that PDE4 inhibition is effective in reducing rodent stress-induced defecation, provides the first functional data on a potential role for PDE4 activity in the colonic evacuation response to stress, and indicates the potential utility of PDE4 inhibitors in functional bowel disease such as irritable bowel syndrome requires further evaluation.

Kv7.2-7.5 voltage-gated potassium channel (KCNQ2-5) opener, retigabine, reduces capsaicin-induced visceral pain in mice

K(v)7.2-7.5 voltage-gated potassium channels (KCNQ2-5) are associated with M-current and known to distribute in the nociceptive sensory pathway (e.g., dorsal root ganglia and spinal cord). Opening of these channels leads to cell membrane hyperpolarization that results in decreased neuronal action potentials. Since, KCNQ/M-current is located in the visceral sensory system, we examined the anti-nociceptive effect of the KCNQ opener, retigabine, on visceral pain induced by an intracolonic injection of capsaicin in mice. Intraperitoneal administration of retigabine (1, 3 and 10 mg/kg) dose-dependently suppressed visceral pain behavior (i.e., the number of licking) induced by the capsaicin treatment and prolonged the latency to first licking. These data provide the first evidence that increased KCNQ channel conductance plays an inhibitory role in the visceral pain pathway.

A new automated and high-throughput system for analysis of the forced swim test in mice based on magnetic field changes

INTRODUCTION

MicroAct (Neuroscience, Tokyo, Japan) was originally developed as a new system for an automated analysis of scratching behaviors in mice. This system is based on the detection of electric current in the coils according to the movement of the magnets implanted in the hind paws. We applied and improved this system to establish an automated analysis system of forced swimming behaviors in mice, which is used as an animal model of depression.

METHODS

One day before the test, male CD-1 mice were attached with a wire ring to their hind paws under inhalation anesthesia. After attaching a small magnet to both of the wire rings, each animal was placed for 6 min in a glass cylinder filled with water, which is surrounded by a coil. The swimming behaviors of the mouse were analyzed for the measurement of duration of immobility, a major marker of depression in rodents, by the detection system (MicroAct). The duration of immobility was also determined by manual measurement using the swimming behavior-recorded videotapes produced at the same time as the automated analysis.

RESULTS

The difference of the duration of immobility between naïve mice and mice with the rings was not significant. The dose-response effect of imipramine (tricyclic antidepressant, 0, 7.5, 15, 30 and 60 mg/kg, p.o.) on the duration of immobility in the last 4-min of the 6-min testing period determined by MicroAct was similar to that assessed by the manual measurement. These data from the two different methods were significantly correlated (r=0.8805). Moreover, throughput of the automated analysis was 15 times more efficient than that of the manual analysis.

DISCUSSION

These results suggest that the automated analysis system of forced swimming of mice using MicroAct can be used as a high-throughput method to examine antidepressive activity of a compound with objectivity and reliability.

Vital role of the itch-scratch response in development of spontaneous dermatitis in NC/Nga mice

BACKGROUND

The itch sensation and the resultant response, scratching, are important symptoms of atopic dermatitis (AD) and have a significant impact on the quality of life of affected patients. However, the influence of the itch-scratch response on the pathology of AD has not been precisely elucidated.

OBJECTIVES

To investigate the role of scratching behaviour in the development of spontaneous dermatitis using conventionally raised NC/Nga mice (Conv-NC mice), which are known to be an animal model for human AD.

METHODS

Capsaicin-sensitive sensory nerves of the mice were ablated by neonatal capsaicin treatment (Cap-NC mice), and the development of spontaneous dermatitis in the Cap-NC mice was compared chronologically with that in Conv-NC mice.

RESULTS

Scratching behaviour was almost completely prevented in Cap-NC mice raised for 84 days under conventional conditions, and the development of dermatitis and elevation of the serum IgE level were significantly suppressed. Histological analysis revealed that the numbers of infiltrating eosinophils and mast cells in the lesional skin of Cap-NC mice were lower than those in Conv-NC mice. Immunological studies showed that the capability of spleen T cells to produce both T-helper (Th) 1 (interferon-gamma) and Th2 [interleukin (IL)-5 and IL-13] cytokines was diminished in Cap-NC mice. Furthermore, serum levels of IL-18 were approximately twice higher in Conv-NC mice than in Cap-NC mice.

CONCLUSIONS

These observations suggest that scratching behaviour contributes to the development of dermatitis by enhancing various immunological responses in the murine AD model, implying that prevention of the itch sensation and/or itch-associated scratching behaviour is an effective treatment for AD.

Sulpiride specifically attenuates psychological stress-induced gastric lesions in rodents

Gastric lesions were developed in the communication box paradigm (CB) in mice as well as in the activity-stress paradigm (AS) in rats. Treatment with sulpiride (10-320 mg/kg, p.o.) attenuated these psychological stress-induced gastric lesions in a dose-dependent manner, while it failed to suppress those induced by physical stress such as restraint water-immersion (WI) and indomethacin treatment (IND). In contrast, treatment with famotidine (0.32-10 mg/kg, p.o.) dose-dependently attenuated the gastric lesions induced by physical stress but not those by psychological stress. Pylorus-ligation study revealed that famotidine strongly reduced gastric acid secretion, whereas sulpiride minimally affected that. It was also demonstrated that physical stress (WI) enhanced acid secretion while psychological stress (CB and AS) rather depressed that. These results suggest that the mechanisms of gastric lesion formation are clearly different between physical and psychological stress and that sulpiride specifically attenuates psychological stress lesions possibly through a central mechanism.

FR121196, a potential antidementia drug, ameliorates the impaired memory of rat in the Morris water maze

We investigated the effects of FR121196 N-(4-acetyl-1-piperazinyl)-4-fluorobenzenesulfonamide on the performance of rats in the Morris water maze using a two-trial-per-day regimen. Escape latency to find the platform was significantly prolonged in young rats subjected to scopolamine (1 mg/kg) treatment or to nucleus basalis magnocellularis (NBM) or fimbria-fornix (FF) lesioning compared with the respective control animals. Similar memory deficit was observed in aged rats (24-26 months old) compared with young rats. Daily treatment with FR121196 (0.1-1.0 mg/kg i.p.) ameliorated all the memory deficits except in the FF-lesioned rats, whereas physostigmine (0.032-0.32 mg/kg) ameliorated the memory deficits in scopolamine-treated rats but not in the NBM-lesioned, FF-lesioned or aged rats. Methamphetamine (0.32-3.2 mg/kg) hardly ameliorated the memory deficits and, rather, aggravated those in the scopolamine-treated, NBM-lesioned and aged rats. Neurochemical analysis of the brain showed that dopamine, norepinephrine and serotonin levels were significantly reduced in the hippocampus of the FF-lesioned rats compared with the sham control, and a significant reduction of dopamine level in the cortex was also observed in the aged rats compared with young rats. None of these parameters were changed after NBM lesioning. We concluded that FR121196 ameliorates the memory deficits of rats with cholinergic dysfunction through the action on the hippocampal monoaminergic (possibly serotonergic) neurons.

The differential roles of sympathetic nerve activity in the pathogenesis of antral and corpus lesions induced by indomethacin in rats

A s.c. dose (32 mg/kg) of indomethacin induced antral ulcers and corpus erosions in refed rats, but almost exclusively corpus erosions in fasted rats. In the refed rats the antral ulcers were not affected by a preganglionic splanchnicectomy, but were significantly attenuated by 6-hydroxydopamine (80 mg/kg i.p.), prazosin (32 mg/kg p.o.), yohimbine (32 mg/kg p.o.) or streptozotocin (80 mg/kg i.v.), whereas the corpus erosions were exaggerated by the latter three treatments. Blood analysis revealed that refeeding of fasted rats caused instant increases in plasma glucose and insulin levels and a subsequent gradual increase in plasma norepinephrine (NE). These plasma parameter changes were hardly affected by an indomethacin treatment. The NE response to refeeding was reversed by 6-hydroxydopamine which minimally affected the glucose and insulin responses. Splanchnicectomy changed none of these responses, although it almost completely depleted plasma epinephrine levels. The NE response was enhanced by yohimbine and prazosin, and the insulin response was enhanced by the former. Streptozotocin abolished the insulin response and reversed the NE response. It is concluded that hyperinsulinemia in response to refeeding induces NE release and results in an activation of alpha-1 and/or alpha-2 adrenergic receptors which plays a permissive role in the indomethacin-induced antral ulcer formation. Conversely, this series of events may play a protective role against the corpus erosion formation.

Enhancement of gastric mucosal blood flow by beta-3 adrenergic agonists prevents indomethacin-induced antral ulcer in the rat

Indomethacin (32 mg/kg s.c.) produced mainly antral ulcers in refed rats but almost exclusively corpus erosions in fasted rats. Subcutaneous doses of a nonselective beta (isoproterenol), a selective beta-2 (salbutamol) and selective beta-3 adrenergic agonists CBRL35135, (R*,R*)-(+/-)-methyl 4-[2-[2-hydroxy-2-(3-chlorophenyl)ethylamino]propyl] phenoxyacetate hydrobromide; CL316,243, disodium (R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxy-ethyl]- amino]propyl]-1,3-benzodioxole-2,2-dicarboxylate; SR58611A, ethyl[(7S)-7-[(2R)-(2(3-chlorophenyl)-2-hydroxyethylamino]5,6,7, 8-tetrahydronaphthalen-2-yloxy]acetate hydrochloride) dose-dependently attenuated the antral ulcers, and their activities were in the order of BRL35135 (ED50 = 0.03 mg/kg) > CL316,243 (ED50 = 0.04 mg/kg) > SR58611A (ED50 = 0.2 mg/kg) > isoproterenol (ED50 = 0.4 mg/kg) > salbutamol (ED50 = 6 mg/kg). Whereas only isoproterenol, salbutamol and BRL35135 significantly attenuated the corpus erosions and reduced gastric acid secretion in pylorus-ligated rats. In in vitro, all the beta agonists enhanced the beating rate of guinea pig atria (beta-1 action) and inhibited spontaneous contractions of rat uterus (beta-2 action) and colon (beta-3 action). There was found a statistically significant correlation between the IC50 values of the drugs on the colon and ED50 values on the indomethacin-induced antral ulcers (r = 0.97). In addition, the beta agonists excepting salbutamol increased antral gastric mucosal blood flow in rats anesthetized with halothane, and the activities were arranged in the potency order of inhibiting colon motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible involvement of hyperinsulinemia and adrenergic activation in the pathogenesis of indomethacin-induced antral ulcers in nonfasted hamsters and refed rats

Subcutaneous doses of indomethacin (IND) produced mainly antral ulcers in refed rats, almost exclusively corpus erosions in fasted rats, but no antral or corpus mucosal insult in nonfasted rats. In contrast, IND-treatment in nonfasted hamsters caused antral ulcers but minimal corpus erosions. Mild and severe hyperinsulinemia were observed in refed rats and nonfasted hamsters, respectively. The hyperinsulinemia and antral ulcers in the animals were significantly attenuated by a pretreatment (80 mg/kg, i.v., in rats, 60 mg/kg, i.p., in hamsters) of streptozotocin. Furthermore, the antral ulcers were dose-dependently attenuated by prazosin, an adrenergic alpha-1 antagonist, and yohimbine, an adrenergic alpha-2 antagonist, but not by propranolol, an adrenergic beta antagonist. The large doses of atropine (3.2-10 mg/kg, p.o.) also attenuated the ulcers. The histamine H2 receptor antagonist, famotidine (1-10 mg/kg, p.o.), significantly attenuated the antral ulcers in nonfasted hamsters, but not in refed rats. The latter two drugs exhibited greater inhibition of the corpus erosions in fasted rats compared with the antral ulcers in refed rats and nonfasted hamsters. The corpus erosions were more extensive after streptozotocin treatment (80 mg/kg, i.v.) and were aggravated significantly by yohimbine, whereas they were hardly affected by prazosin or propranolol. It is thus concluded that hyperinsulinemia and adrenergic activation are commonly involved in the etiology of the IND-induced antral ulcers in refed rats and nonfasted hamsters. Vagal activity, which plays a crucial role in the etiology of the corpus erosions in fasted rats, may play a part in the antral ulcer formation in nonfasted hamsters, but not in refed rats.