Enhancement of morphine antinociception by ibogaine and noribogaine in morphine-tolerant mice

BACKGROUND: The authors evaluated and compared the efficacy of 20 mg versus 40 mg of paroxetine in a randomized, double-blind, parallel-group study during a maintenance period of 28 months. METHOD: Ninety-nine inpatients with recurrent, unipolar depression (DSM-IV criteria) who had at least 1 depressive episode during the 18 months preceding the index episode were openly treated with paroxetine 40 mg/day. Seventy-two subjects had a stable response (Hamilton Rating Scale for Depression score < 8) to paroxetine treatment and remained in the continuation treatment as outpatients for 4 months. At the time of recovery, 68 patients were randomly assigned to 1 of the 2 maintenance treatment groups: paroxetine 20 mg or paroxetine 40 mg daily. RESULTS: Sixty-seven patients completed the 28-month follow-up period. Seventeen (51.5%) of 33 patients in the 20-mg paroxetine regimen had a single recurrence compared with 8 (23.5%) of 34 subjects in the 40-mg dose regimen (chi2 = 5.56, p = .018). CONCLUSION: These data suggest that a full dose of paroxetine is recommended in unipolar patients who are at high risk for recurrent depressive episodes.     

Behavioral effects of atriopeptin in rats

High densities of atriopeptin-immunoreactive fibers and of highly specific and selective atriopeptin receptor sites are present in brain areas involved in animal behavior. The possible influence of these peptides on behavior was thus investigated in adult rats. The intracerebroventricular injection of atriopeptin II modified male sexual behavior (reduction in mount latency) at the dose of 5 micrograms/animal; lower and higher doses were ineffective. Open-field behavior was also modified by i.c.v. atriopeptin II at the doses of 5 and 10 micrograms/rat, which induced an increase in the number of external and internal crossings and of external rearings. Finally, in fasted rats, atriopeptin II, at the dose of 10 micrograms/rat, significantly increased the amount of food intake 30 and 60 min after injection. These findings indicate that atriopeptins may modify different animal behaviors.     

Central effects of dehydroepiandrosterone in Zucker rats

OBJECTIVES: To investigate whether dehydroepiandrosterone (DHEA), an adrenal/gonadal androgen, can act centrally to reduce energy intake in a model of genetic obesity, the Zucker fatty rat. To investigate a possible mechanism of action. DESIGN: Two experiments were performed in lean and obese female Zucker rats. In the first experiment, 24 h following administration of i.p. DHEA (200 mg/kg), three hypothalamic regions [lateral hypothalamus (LH), ventromedial nucleus (VMH), and paraventricular nucleus (PVN)] were analyzed for monoamine neurotransmitter concentrations. In the second experiment, DHEA (50 micrograms) was administered by i.c.v. injection. Energy intake for the following day was measured. MEASUREMENTS: In the first experiment, concentrations of norepinephrine (NE), epinephrine (EPI), dopamine (DA), serotonin (5HT), the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) were measured. Ratios of 5HT/5HIAA were calculated. In the second experiment, kilojoules consumed per 24 h were calculated. RESULTS: All LH monoamines, and PVN DA, displayed lower concentrations in obese than lean control rats. DHEA treatment reversed these reductions in obese rats without affecting lean rats. DHEA increased VMH EPI in obese rats only. DHEA increased PVN NE in both lean and obese rats. I.C.V. DHEA decreased energy intake in obese but not lean rats. CONCLUSION: The i.c.v. results suggest that DHEA exerts a phenotype specific, centrally mediated inhibitory effect on food intake. In addition, in doses previously shown to reduce energy intake in obese but not lean rats, i.p. DHEA reversed reduced concentrations of many monoamines, particularly in the LH, in obese animals only. These latter changes provide indirect evidence to suggest that these central neurotransmitters may play an important role in the antiobesity effect of DHEA in the Zucker fatty rat.     

Antagonism of etonitazene''s effects in rats and pigeons

The effect of a proteolytic enzyme, pronase, on material present in cisternae of the granular endoplasmic reticulum of mole pinealocytes demonstrates their proteinaceous nature.     

The effects of propranolol HCl in hippocampal-lesioned rats

Experiments were conducted to determine the effects of propranolol administration in rats lesioned in the hippocampal area. Chronic oral administration of propranolol to intact rats produced a significant decrease in mean systolic blood pressure. No significant changes in blood pressure were produced with propranolol treatment in rats lesioned in the septal or anterior hypothalamic areas, whereas, in rats lesioned in the hippocampal area, a significant elevation of blood pressure was observed. These findings confirm previous results that suggest that the hypotensive effects observed with chronic propranolol administration are mediated via the hippocampus.     

Contrast effects in escape conditioning of rats.

In Exp I 39 male Holtzman albino rats ran for 20 trials from an alley where they received .2-, .4-, or .8-ma shocks to a goal box where there was no shock. All Ss were then shifted to .4 ma in the alley for 20 trials. Results show that rapid adjustment of running speeds occurred with shifts in amount of escapable shock. More importantly, however, positive and negative contrast occurred. In Exp I an experimental group (n = 10) received .2 ma on half of the trials and .4 ma on the other half, and 2 control groups (n = 10) received either .4 or .2 ma on all trials. Results show that the experimental group escaped faster on .4-ma trials than the .4-ma control group (positive contrast) and escaped more slowly on .2-ma trials than the .2-ma control (negative contrast). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypotensive effects of peptide T in conscious rats

1. The present study investigated the effects of peptide T on mean arterial blood pressure (MAP) in conscious normotensive Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHR) and two-kidney one-clip (2K1C) hypertensive rats. 2. Peptide T was infused via the left jugular vein at a rate of 1 mg/kg per h in SD, SHR and 2K1C rats and then at doses of 0.1, 0.25, 0.5, 1 and 5 mg/kg per h in SHR, with 0.9% saline as a sham control in SHR and 2K1C. Mean arterial pressure was measured directly before, during and after infusion. 3. Peptide T (1 mg/kg per h) decreased blood pressure in both SHR (P < 0.01) and 2K1C (P < 0.05). In normotensive SD rats the fall in MAP approached statistical significance (P = 0.06). The effect of peptide T was not significantly different in normotensive compared with hypertensive rats. Saline infusion had no effect. The blood pressure lowering effect of peptide T appeared to be dose-dependent in SHR.     

Endocrine and behavioral effects of airpuff-startle in rats

Computerized tests of neurobehavioral function are frequently administered in neurotoxicological studies with little attention given to the optical properties of test stimuli or to the vision of subjects. Yet many test stimuli are small or briefly presented, and test endpoints often involve short reaction times. Stimulus detection and reaction time are known to be strongly dependent upon stimulus luminance, contrast, and size, as well as on the subject's visual abilities. The current study assessed the influence of visual contrast sensitivity on Neurobehavioral Evaluation System 2 (NES2) test results in three data sets. Analyses indicated that vision was associated with up to 24% of the variance (Hand Eye Coordination test) in NES2 scores, even when visual acuity was normal, and that vision often influenced the significance of group differences. It is suggested that researchers measure the luminance, contrast, and size of test stimuli, the distance from the subject's eyes to the monitor, and the subject's visual contrast sensitivity. The measurement and control of stimulus parameters and the inclusion of visual function scores in analysis models could reduce the variability among computerized test scores both within and between studies. Models that assess the influence of vision on computerized test results may help to identify the CNS domains and specialized functions adversely affected by neurotoxicant exposures.     

Anxiolytic effects of cytotoxic hippocampal lesions in rats.

Rats with cytotoxic lesions of the hippocampus were given 3 anxiety tests: social interaction with a novel rat, the elevated zero-maze (a modification of the plus-maze), and hyponeophagia (eating familiar and novel foods in a novel place). Marked anxiolytic effects were seen in the social interaction and hyponeophagia tests, but not on the zero-maze. These results confirm and extend previous experiments that used traditional lesion techniques. The zero-maze result was consistent with other experiments using the plus-maze, in which intrahippocampal administrations of pharmacological agents were not anxiolytic, although variability in ethological tests may also be a factor. As the hyponeophagia test used an elevated apparatus, as in the zero- and plus-mazes, the lack of a lesion effect in the zero-maze was unlikely to have been due to an inability to relieve height-induced anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral effects of differential experience in hypophysectomized rats.

Examined whether the effects of enriched and impoverished environments on brain chemistry and weights in rats may be mediated hormonally. 3 experiments were done on 78 male Fischer and Long-Evans rats hypophysectomized at about 30 days and on normal controls. Environmental treatments lasted about 35-65 days of age. Among operates as among controls the enriched-environment Ss showed significantly greater cortical weight, decreased cortical acetylcholinesterase (AChE)/weight, and increased cholinesterase (ChE)/AChE. Thus these effects of differential environment do not require mediation by hormones of the pituitary or those regulated by the pituitary. Hypophysectomized Ss had significantly lower brain weights, lower cortical AChE/weight, and greater cortical ChE/AChE than did controls. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immunoregulatory effects of ginsenoside Rg1 in aged rats

It has been well documented that the immune function declines with age in the human and animals. The possible causes for the decline are the inability of lymphocytes to proliferate in response to mitogenic stimulation and the decrease of IL-2 production. In the present studies, Rg1 was shown to selectively enhance the proliferation of lymphocytes and the production of IL-2 in aged rats. Using Northern blot and Western blot analyses, Rg1 was found to promote IL-2 gene expression which showed increase of IL-2 mRNA and IL-2 protein contents. Interestingly, under the same conditions, studies were carried out on the effect of Rg1 on the immune function of young adult rats, but no marked influence was observed. According to these results, it is reasonable to consider Rg1 an immunoregulator rather than a purely "immunopotentiating agent".     

The effects of cyclophosphamide on pulmonary thrombopoiesis in rats

Cyclophosphamide (CP), an antineoplastic and immunosuppressive agent, even when administered in large doses, slightly affects the quantity of blood platelets. The aim of the present study was to analyse the effect of single intraperitoneal administration of CP (150 mg/kg b.w.) on the quantitative changes in platelets obtained from the left and right ventricle of the heart, as well as to evaluate the occurrence of megakaryocytes in lung tissue depending on the period of time that passed from CP administration. In control subgroups, fewer platelets were found in the blood collected from the RV compared with the left ventricle at all time intervals. After 1 and 3 days following i.p. administration of CP, a decrease was observed in the number of platelets both in the blood from the right ventricle and left ventricle when compared with control. However, after 14 days, the number of platelets in the blood from the left ventricle was higher, compared with the left ventricle and right ventricle of control animals, and significantly higher (p < 0.001747), compared with their number obtained from the right ventricle of CP-receiving animals. Simultaneous ultrastructural examinations with transmission electron microscopy revealed the increased number of platelets in the lung vascular bed of CP-receiving rats at all time intervals. However, megakaryocytes were found 7 and 14 days after administration of CP. The findings clearly indicate that the lungs could be a major place of thrombopoiesis following therapy with a single large dose of CP.     

The effects of intrathecal clonidine in spontaneously hypertensive rats

The relationship between intrathecal clonidine and hypertension was investigated in SHR rat and WKY rat. After the animals were given clonidine 15 micrograms into the lumbar intrathecal space, blood pressure, heart rate and respiratory rate were recorded for 60 minutes under nembutal anesthesia. Percent change of mean blood pressure was significantly larger in SHR rat than in WKY rat at 50 and 60 minutes after clonidine injection. No difference was observed in percent change of heart rate and respiratory rate. The results suggest the possibility that lumbar intrathecal clonidine injection produces greater hypotension in hypertensive subjects than in normotensive subjects.     

Differential effects of ethanol in adolescent and adult rats

Alcohol use in children and adolescents is widespread. However, very little is known about the effects of alcohol exposure during this period of postnatal development. The goal of the present study was to compare the relative sensitivity to the sedative effects of alcohol in periadolescent and adult rats. After treatment with either 4 or 5 g/kg ethanol, both 20- and 30-day-old rats regained their righting reflex significantly earlier than 60-day old rats. In 30-day-old rats, serum ethanol concentrations (SECs) were significantly greater at the time of the recovery of the righting reflex than 60-day-old rats. Developmental differences in the effects of ethanol on locomotor activity were also observed. In 60-day-old rats, 2.5 g/kg ethanol generally decreased locomotor activity. Ethanol did not significantly alter locomotor activity in 20- and 30-day-old rats. Finally there were significant developmental differences in the pharmacokinetics of ethanol with a significant delay in the time to peak SECs in 60-day-old rats relative to 20- and 30-day-old rats. These findings indicate that peri-adolescent rats are less sensitive to the sedative effects of ethanol as they recovered their righting reflex earlier and at significantly higher SECs than adult rats.     

Pathophysiological effects of hemodilution in chronic mountain sickness in rats

We examined the effect of isovolemic hemodilution in a rat model of chronic mountain sickness (CMS). After 30 days at simulated high altitude (5,500 m), Hilltop rats had developed evidence of CMS: severe hypoxemia, polycythemia, and pulmonary arterial hypertension. Isovolemic hemodilution to a mean hematocrit of 46 +/- 5% was well tolerated by both the hypoxia-sensitive Hilltop rats and the companion Madison rat strain that does not develop CMS. After hemodilution, we found no evidence of sustained improvements in ventilation or gas exchange in either strain. Despite the fall in blood viscosity, cardiac output increased only marginally, and pulmonary arterial hypertension persisted in the Hilltop rats. Vascular hindrance increased after hemodilution, preventing a significant decline in pulmonary and systemic vascular resistances in the Hilltop rats. Blood O2 content and the coefficient of O2 delivery fell after hemodilution, but O2 consumption was sustained at a normal level after hemodilution by increasing the extraction fraction in the Hilltop strain. There was systemic hypotension through the first day of hemodilution, but this was the only apparent adverse effect of hemodilution. We conclude that isovolemic hemodilution was well tolerated despite the reduction in tissue O2 delivery. However, hemodilution failed to improve any of the respiratory and cardiovascular manifestations of CMS in Hilltop rats.     

Sexually dimorphic effects of anti-NGF treatment in neonatal rats

To investigate the sensitivity to changes in excitability of motoneuron pool dependent on voluntary motor commands, we recorded motor evoked potentials (MEPs) and H-reflexes from the right flexor carpi radialis (FCR) muscle of normal human subjects. Amplitudes of MEPs were always larger than those of the H-reflex in both tonic and phasic muscle contractions. Furthermore, amplitudes of MEP and H-reflex were larger in phasic than in tonic muscle contraction. These results indicate that there are differences in the sensitivity to changes in motoneuronal excitability related to the production of excitatory postsynaptic potentials for H-reflex and MEP responses, respectively.     

Nicotine-like discriminative stimulus effects of bupropion in rats.

Bupropion, a tobacco-cessation product, shares discriminative stimulus effects with cocaine and methamphetamine. The discriminative stimulus effects of these drugs, in turn, overlap with those of nicotine. This study investigated the overlap in discriminative stimulus effects of bupropion and nicotine. Rats were trained to discriminate 0.4 mg/kg (-)-nicotine from saline in 2-lever drug discrimination. Both nicotine and bupropion substituted for nicotine: however nicotine's effects were blocked by the nicotinic antagonist mecamylamine, whereas those of bupropion were not. These results suggest that bupropion may be producing its nicotine-like discriminative stimulus effect though a different mechanism that nicotine. Give bupropion's shared pharmacology with dopamine transport inhibitors, these effects may be produced in part through bupropion's actions on dopaminergic neurotransmission. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential conditioning and contrast effects in rats.

Considers previous research, using a differential conditioning procedure to examine contrast effects in the runway, inadequate due to the operation of a ceiling effect and/or a decision-time problem. A special procedure (delay of reward and massing trials) was used to solve these problems in an experiment with 40 male Holtzman albino rats. Results reveal reliable positive and negative contrast effects. Data support the conclusions, that (a) it is reasonable to seek a common explanation of behavioral contrast (operant) and incentive contrast (runway) data; (b) perceptual theories of contrast, predicting both positive and negative contrast, are to be preferred over theories designed to predict only negative contrast; and (c) the type of response, and extraneous variables which affect it, needs to be carefully considered in dealing with reward manipulations. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparative study of anxiogenic effects of fluoroquinolones in rats

It is well known that the removal of a fixation point prior to the presentation of a peripheral target dramatically reduces saccadic reaction time (SRT). This effect has become known as the "gap effect". The present study examined several detailed kinematic variables to determine whether the removal of the fixation point also affects the manner in which saccades are produced. The findings indicate that saccades that were initiated after the removal of the fixation point had higher average velocities and reached greater peak velocities, accelerations, and decelerations than did saccades produced in the presence of the fixation point. The results suggest that the removal of the fixation point may affect the force-time curves of saccades in addition to affecting the time needed to initiate the saccades.