Quantitative assessment of the microstructure of rat behavior: II. Distinctive effects of dopamine releasers and uptake inhibitors

The effects of four indirect dopamine agonists,d-amphetamine (0.25–4.0 mg/kg), cocaine (2.5–40.0 mg/kg), GBR 12909 (10.0–30.0 mg/kg), and nomifensine (5.0–20.0 mg/kg), on the behavioral organization of movements in an unconditioned motor paradigm were investigated in rats. The extended scaling hypothesis using the fluctuation spectrum of local spatial scaling exponents was used to quantify the geometrical characteristics of movements. The results reveal a qualitatively similar disruption of behavioral organization by lower doses of these drugs. Specifically, rats treated withd-amphetamine (<2.0 mg/kg), cocaine (<20.0 mg/kg), GBR 12909 (<20.0 mg/kg), or nomifensine (<10.0 mg/kg) exhibited a reduced range in the fluctuation spectrum, reflecting a predominance of meandering movements with local spatial scaling exponents between 1.3 and 1.7. This reduction was accompanied dynamically by a reduced predictability of movement sequences as measured by the dynamical entropy,h. By contrast, higher doses of these drugs produced distinctly different changes in behavioral organization. In particular, 4.0 mg/kgd-amphetamine and 40.0 mg/kg cocaine increased the fluctuation range, reflecting relative increases in both straight and circumscribed movements that are interpreted as a combination of spatially extended and local perseveration. In contrast, high doses of 30.0 mg/kg GBR 12909 and 20.0 mg/kg nomifensine induced only local perseveration. High doses ofd-amphetamine, cocaine, GBR 12909 and nomifensine reduced the dynamical entropy,h, indicating an increased predictability of the movement sequences. These results suggest that the generic behavioral change induced by low doses of dopamine agonists is characterized by a reduced variety of path patterns coupled with an increased variability in sequential movement sequences. The differential effects of higher doses of these drugs may be due to their influences on other neurotransmitter systems or differential affinities for different dopamine subsystems.     

Expression of the hyperpolarization-activated current, I(f), in cultured adult rat ventricular cardiomyocytes and its modulation by hypertrophic factors.

The hyperpolarization-activated, cyclic nucleotide-gated (HCN) current, I(f), is typically overexpressed in myocytes from hypertrophied and failing hearts, where it may play an arrhythmogenic role. Signaling pathways activated by agonists such as angiotensin-II, endothelin-1 and phenylephrine, via G protein-coupled receptors (GPCR), promote myocardial hypertrophy, but their effect on cellular electrophysiological remodeling, particularly I(f) expression is largely unknown. Thus, I(f) expression was measured by patch-clamp and quantitative RT-PCR measurement in cultured adult rat ventricular cardiomyocytes (VCM) exposed to different culture conditions, that is, in the absence or presence of: fetal bovine serum (FBS, 5%), 0.1 microM angiotensin-II, 0.1 microM endothelin-1 or 20 microM phenylephrine. Membrane capacitance (C(m)) was used to estimate cell size and current density in patch-clamped VCM. At 8 days of culture, about 60% of VCM showed I(f). In serum-free medium, I(f) density was increased by phenylephrine (2.28+/-0.51 vs. 0.84+/-0.30 pA/pF in CTR, p<0.05) and endothelin-1 (2.20+/-0.38 vs. 1.03+/-0.34 pA/pF in control, p<0.05), not by angiotensin-II (1.60+/-0.50 pA/pF, not significant vs. control). Similarly, in cells cultured with 5% FBS, phenylephrine and endothelin-1 significantly increased I(f) density by 159.3% and 59.5% (p<0.05 vs. untreated cells), while angiotensin-II did not modify it. The effect of endothelin-1 was abolished by using the selective endothelin receptor type A (ET(1A)) antagonist BQ-123 (1 microM). mRNA levels for HCN2 and HCN4 were significantly increased during in vitro culture; exposure to endothelin-1 increased HCN2 mRNA. A similar pattern of I(f) overexpression was detected in hypertrophied left ventricular cardiomyocytes from old hypertensive rats. Thus, adult VCM in primary culture undergo changes in I(f) expression reminiscent of in vivo hypertrophy; endothelin-1 (but no angiotensin-II) seems to play a role in ionic remodeling.     

The effects of methadone on the social behavior and activity of the rat

Pairs of 80-day-old female rats were given SC injections of either 0, 1, 2.5, or 4 mg/kg of methadone hydrochloride on each of 6 days. Both animals of the pair received the same dose. One hour postinjection, each pair was observed in a circular arena for a five minute period during which the following dependent measures were recorded: total time in contact, latency to initial contact, frequency of aggressive grooms, and locomotor activity. The results indicated that the rats with methadone spent less time in contact, took longer to contact, and aggressively groomed each other less frequently than rats treated with a saline vehicle. Also, the results suggested that the disruption of social behavior produced by methadone was not a reflection of decreased activity levels.     

The neurotoxicity of radiosensitizing drugs: a biochemical assessment of desmethylmisonidazole (DMM) in the rat

This study evaluates a major metabolite of misonidazole, desmethylmisonidazole, for its potential to induce peripheral nerve damage using the lysosomal enzyme correlates of neuropathological change, namely beta-glucuronidase and beta-galactosidase. The results showed that desmethylmisonidazole like misonidazole had a similar potential for inducing peripheral nerve damage as measured biochemically, but the dosing regimen had to be maintained for 10 consecutive days as opposed to the 7 days required for misonidazole.     

Novelty-oriented behavior in the rat after selective damage of locus coeruleus projections by DSP-4, a new noradrenergic neurotoxin

Open-field behavior and reactions to a novel object (white-colored cube) or a familiar object (drinking bottle) were investigated in rats treated with DSP-4 N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, a new noradrenergic neurotoxin which selectively damages locus coeruleus projections. Altered behavior in the open-field and in the presence of the novel object (white cube) was observed in DSP-4 rats. This was reflected in decreased exploration-oriented locomotor responses and in longer latencies to approach the novel cube. Also, there was a trend towards fewer center entries and a shorter duration of object exploration. Although these behavioral responses of DSP-4 rats were indicative of enhanced neophobia, other measures of emotionality, such as grooming and defecation, were either unchanged or slightly decreased. Moreover, when the familiar drinking bottle was present in the open-field, water-deprived DSP-4 rats showed no change in any measure of fear including the latency to the first approach and lick, and the duration of the licking episodes. The results of this study suggest that noradrenergic neurons of the locus coeruleus are involved in the regulation of certain, but not all, novelty-oriented responses in the rat. Explorative behavior in the novel environment seems to be particularly dependent on central noradrenaline.     

Formulation of fenbufen suppositories. I. quantitative histological assessment of the rectal mucosa of rats following treatment with suppository bases

Quantitative histology was used to assess the interaction of suppositories of hard fats (Suppocire AP and OS1X; Witepsol H12 and H19) and polyethylene glycol (PEG 1500) with the rectal mucosa of rats. All bases significantly increased epithelial cell loss but only following PEG treatment was the natural capacity of the epithelium to resist disruption exceeded, thereby resulting in areas of complete desquamation with a bare basal lamina. On the basis of these data it was possible to rank the interaction of the suppositories with the rectal lining; Suppocire OS1X < Suppocire AP = Witepsol H12 < H19 < PEG 1500.     

Anxiogenic and aversive effects of corticotropin-releasing factor (CRF) in the bed nucleus of the stria terminalis in the rat: role of CRF receptor subtypes

Rationale Corticotropin-releasing factor (CRF) produces anxiety-like and aversive effects when infused directly into the various regions of the brain, including the bed nucleus of the stria terminalis (BNST). However, the CRF receptor subtypes within the BNST mediating these phenomena have not been established.Objectives We used selective CRF receptor antagonists to determine the receptor subtypes involved in the anxiogenic-like and aversive effects CRF in the BNST.Materials and methods Male Long–Evans rats were bilaterally infused with CRF (0.2 or 1.0 nmol) either alone or in combination with the CRF₁ receptor antagonist CP154,526 or the CRF₂ receptor antagonist anti-sauvagine 30 (AS30) before behavioral testing in the elevated plus maze or place conditioning paradigms.Results Intra-BNST administration of CRF produced a dose-dependent reduction in open arm entries and open arm time in the elevated plus maze, indicating an anxiogenic-like effect. These effects were inhibited by co-infusion of CP154,526 but not of AS30, indicating that the anxiogenic-like effects of CRF in the BNST are mediated by CRF₁ receptors. Place conditioning with intra-BNST administration of CRF produced a dose-dependent aversion to the CRF-paired environment that was prevented by co-infusion of either CP154,526 or AS30, indicating that both CRF receptor subtypes mediate the aversive effects of this peptide. Intra-BNST infusions of the CRF receptor antagonists alone produced no effects in either behavioral paradigm.Conclusions CRF₁ receptors in the BNST mediate the anxiogenic-like effects of CRF in this region, whereas both CRF₁ and CRF₂ receptor subtypes mediate the conditioned aversive effects of this peptide within the BNST.     

Effects of pre- and postnatal exposure to the UV-filter octyl methoxycinnamate (OMC) on the reproductive, auditory and neurological development of rat offspring

Octyl Methoxycinnamate (OMC) is a frequently used UV-filter in sunscreens and other cosmetics. The aim of the present study was to address the potential endocrine disrupting properties of OMC, and to investigate how OMC induced changes in thyroid hormone levels would be related to the neurological development of treated offspring.Groups of 14-18 pregnant Wistar rats were dosed with 0, 500, 750 or 1000 mg OMC/kg bw/day during gestation and lactation. Serum thyroxine (T₄), testosterone, estradiol and progesterone levels were measured in dams and offspring. Anogenital distance, nipple retention, postnatal growth and timing of sexual maturation were assessed. On postnatal day 16, gene expression in prostate and testes, and weight and histopathology of the thyroid gland, liver, adrenals, prostate, testes, epididymis and ovaries were measured. After weaning, offspring were evaluated in a battery of behavioral and neurophysiological tests, including tests of activity, startle response, cognitive and auditory function. In adult animals, reproductive organ weights and semen quality were investigated.Thyroxine (T₄) levels showed a very marked decrease during the dosing period in all dosed dams, but were less severely affected in the offspring. On postnatal day 16, high dose male offspring showed reduced relative prostate and testis weights, and a dose-dependent decrease in testosterone levels. In OMC exposed female offspring, motor activity levels were decreased, while low and high dose males showed improved spatial learning abilities. The observed behavioral changes were probably not mediated solely by early T₄ deficiencies, as the observed effects differed from those seen in other studies of developmental hypothyroxinemia. At eight months of age, sperm counts were reduced in all three OMC-dosed groups, and prostate weights were reduced in the highest dose group. Taken together, these results indicate that perinatal OMC-exposure can affect both the reproductive and neurological development of rat offspring, which may be a cause of concern, as humans are systematically exposed to the compound through usage of sunscreens and other cosmetics.     

Delta-9-tetrahydrocannabinol, EEG and behavior:the importance of adaptation to the testing milieu.

Delta-9-Tetrahydrocannabinol (delta-9-THC) in doses of 0.01, 0.05, 0.1, 0.5, and 1.0 mg/kg, i.v. was administered to adult rabbits previously adapted to the testing chamber. Additionally, a group of rabbits not adapted to any part of the testing regimen was administered 1.0 mg/kg delta-9-THC. Cortical and hippocampal electroencephalographs as well as postural and activity behaviors of the unrestrained animals were recorded. In the adapted rabbits, there were dose-related increased in cortical voltage output, disruption of hippocampal theta rhythm and cortical polyspike bursts. Behaviorally, there was a dose-related tendency for standing and exploration to decrease, and at 0.5 and 1.0 mg/lh, delta-9-THC produced sprawling. In the nonadapted rabbits, administration of 1.0 mg/kh of the drug caused EEG and behavioral stimulation followed by depression of both, The results suggest that the bahavioral actions of cannabinols are largely dependent upon the animal's existing state of arousal.     

The effects of intracranial administration of hallucinogens on operant behavior in the rat. I. Lysergic acid diethylamide

Lysergic acid diethylamide (LSD) was infused in one microliter volumes into discrete brain regions of rats trained to press a bar for food reinforcement. The sites were chosen as major areas of the brain 5-hydroxytryptamine (5HT) system: the dorsal and median raphe nuclei, dorsal hippocampus, lateral habenular nuclei, and the prefrontal cortex. Following training in a fixed ratio-40 (FR-40) operant behavior rats were implanted for the lateral habenular nuclei, dorsal hippocampus and the prefrontal cortex. Following recovery from surgery, LSD (8.6 to 86 micrograms) or vehicle was infused immediately before a daily operant session. Infusion of vehicle was inactive. LSD produced a dose-dependent decrease in reinforcements and an increase in 10-sec periods of non-responding (pause intervals). LSD was significantly more potent when infused into the dorsal raphe nucleus than following intracerebroventricular (ICV) administration, whereas LSD was less potent when infused into the median raphe, lateral habenula or dorsal hippocampus. ED50s for increases in pause intervals were 9, 13, 23, 25, and 54 micrograms for infusion into the dorsal raphe, prefrontal cortex, dorsal hippocampus, median raphe, and lateral habenular nuclei, respectively. The ED50 for ICV administration in a previous study was 15 micrograms. The ED50 of LSD placed into the prefrontal cortex did not differ significantly from that of the ICV infusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of chlordiazepoxide (Librium) on the intensity and habituation of agonistic behavior in male Siamese fighting fish

The effects of chlordiazepoxide (Librium) on the intensity and habituation of the threat display in male Siamese fighting fish (Betta splendens) was evaluated by exposing each subject to a male conspecific eliciting stimulus. In an independent groups design, the subjects were tested in either plain tap water, or a drug solution of 15 g/ml or 30 g/ml. Chlordiazepoxide attenuated threat behavior and facilitated habituation of the display without inducing noticeable sedation. The results were evaluated in term of a sdual-process theory of habituation involving independent hypothetical processes of sensitization and habituation which produce the net observed habituation.This research was supported by a National Science Foundation Institutional Development Grant to Earlham College and Grant AYE-8525 from the National Science Foundation awarded to the author. Portions of this research were presented at the Eastern Psychological Association meetings, Boston, 1972. The chlordiazepoxide (Librium) was supplied by Hoffmann-La Roche, Inc., Nutley, New Jersey, U.S.A.     

The effect of dantrolene sodium on rat skeletal muscle in relation to the plasma concentration.

Dantrolene sodium is a muscle relaxant used in the treatment of spasticity. It has been shown to interfere with calcium release from the sarcoplasmic reticulum and thus to inhibit excitation--contraction coupling. The effect of dantrolene sodium on the twitch tension of the tibialis anterior muscle of the rat was measured after 2 mg/kg i.v. or 25 mg/kg orally. Plasma concentrations were estimated at maximum twitch depression and during recovery from the block. In a separate series of experiments the half-life of labelled dantrolene sodium was measured in blood plasma, skeletal muscle and heart muscle of rats. Dantrolene sodium 2 mg/kg i.v. gave a maximal block of approximately 47%, the mean dantrolene sodium concentration was then 5.8 microgram/ml. A half-life for distribution of 1.1 min and an elimination half-life of 31 min after intravenous administration were observed, elimination rate constants in skeletal and heart muscle were comparable. Recovery from the block went much slower, the half-time of the process being approximately 80 min. Dantrolene sodium 25 mg/kg orally gave a maximal block of approximately 38% at a mean plasma concentration of 3.6 microgram/ml after 14 min. The recovery was again very slow. These experiments demonstrated that dantrolene sodium acts according to a two-compartment pharmacokinetic model. There was a discrepancy between duration of effect and plasma concentration of dantrolene sodium in the rat. This suggests that the receptor for dantrolene sodium is not located in the central compartment.     

Differential antagonism of the effects of dopamine D1-receptor agonists on feeding behavior in the rat

A series of experiments was conducted to examine the effects of dopamine D₁ receptor agonists on food intake in rats. In the first experiment, the D₁ agonist SKF 38393 (3.0–30.0 mg/kg) dose-dependently suppressed feeding during a 40 min food-access period, both in food-deprived rats and in non-deprived rats fed a highly palatable diet. Non-deprived rats were more sensitive to these effects of SKF 38393. Using the limited-access, food-deprivation procedure, a comparison was made between the anorectic effects of three D₁ agonists with differing intrinsic efficacies and receptor selectivities. Rank order of potencies for reducing food intake was SKF 82958 > SKF 77434 > SKF 38393 (ED₅₀ values: 0.7, 3.6 and 15.7 mg/kg, respectively). Dose-related, surmountable antagonism by the D₁ antagonist SCH 23390 (0.01 and 0.03 mg/kg) was only obtained with SKF 82958 (0.1–10.0 mg/kg). In contrast to the other compounds, the effects of SKF 38393 were not appreciably altered by the D₁ antagonist. The effects of SKF 82958 were also antagonized by the D₂ receptor antagonist spiperone (0.05 and 0.1 mg/kg), although not in a dose-dependent manner. The present results support a role for D₁ receptors in central feeding mechanisms. They also suggest that the effects of SKF 38393 on feeding may not be mediated exclusively by the D₁ receptor and, further, that SKF 38393 may not serve well in behavioral studies as a prototypical D₁ agonist. The results also demonstrate the need for comparisons among several compounds in studies of D₁ mediated behavioral effects.     

Amphetamine,apomorphine and investigatory behavior in the rat: Analysis of the structure and pattern of responses

In the present experiments, the effects of a wide range of doses of d-amphetamine and apomorphine were studied on investigatory behavior in an automated eight-hole box. Amphetamine (0.125, 0.25, 0.5, 1.0, 3.0, 5.0 mg/kg) increased frequency and total duration of responses, and decreased mean duration in a dose-dependent manner. The strategy and organization of responses, as measured by the order of hole-visits and hole-switching, were unchanged at lower doses of amphetamine but were altered at higher doses. Perseverative hole-poking was observed at the highest dose (5.0) as indicated by increased number of hole-pokes per hole-visit. Apomorphine (0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 mg/kg) decreased mean duration of responses, but in contrast to amphetamine markedly diminished frequency. Locomotor activity was also measured at all doses of both drugs. Our observations indicate that these two stimulant drugs both of which increase motor activity, have markedly different effects on investigatory responses. It is likely that amphetamine increases prepotent response tendencies (i.e., hole-poking), although this does not necessarily reflect enhanced exploration. Further, the results obtained with amphetamine support predictions made by the Lyon-Robbins behavioral theory of amphetamine effects.     

Neuropharmacological profile of R 18 503-induced wet-shake behavior in the rat: Noradrenergic and opiate components

R 18 503 (α-(p-chlorophenyl)-β, β-dimethylimidazole-1-ethanol) 40 mg/kg IP produced a mean of 168 (SEM ± 4) wet shakes in the 35 min following its administration to 100 g male Wistar rats. No other behavioural abnormalities were seen at this dose. The wet-shakes were not caused by reduced body temperature. However, 20–30 min after R 18 503, body temperature was significantly elevated in comparison with saline treated controls. This supports a role for wet-shakes in thermogenesis in the rat, but suggests that R 18 503-induced wet-shakes are not adapted towards the maintenance temperature homeostasis. R 18 503-induced wet-shakes were potently antagonized by 5 narcotic analgesics, but not by aspirin-like drugs. A further 18 non-narcotic compounds including putative serotonin antagonists, neuroleptics and compounds thought to act on the α-adrenergic system, also antagonized R 18 503-induced wet-shakes. Spectral map analysis showed a close link between ED₅₀-values of the non-narcotic R 18 503 wet-shake antagonists and their ED₅₀'s to antagonize noradrenaline-induced lethality; this was further confirmed by a highly significant Spearman Rank correlation between the two test (r_s = 0.77, p<0.001). However, the spectral mapping and Spearman correlation analysis showed no relationship between antagonism of R 18 503-induced wet-shakes and antagonism of apomorphine-induced stereotypy, tryptamine-induced bilateral forepaw clonus, mescaline- induced head twitches, and 5-HT-induced contractions of rat caudal artery. It is postulated that R 18 503-induced wet-shakes result from an interaction between the opiate system and the α-adrenergic system.     

The fate of dibenz[b,f]-1,4-oxazepine (CR) in the rat, rhesus monkey and guinea-pig. Part I. Metabolism in vivo

The fate of dibenz[b,f]-1,4-[11(14)-C]oxazepine (CR) in rats, rhesus monkey and guinea-pig and in isolated perfused rat livers has been examined. 14C-CR was administered to rats at doses from 1.56 to 3470 mumol/kg and irrespective of dose or route of administration most (59-93%) was eliminated in the urine as primarily the sulphates of the 7-, 4- and 9-hydroxylated 10,11-dihydrodibenz[b,f]-1,4-oxazepine-11(10H)-one. In blood, both in vivo and in liver perfusates, CR concentrations decreased biphasically to be replaced initially with CR-lactam (dihydrodibenz[b,f]-1,4-oxazepine-11(10H)-one), followed by the sulphates of the 7-, 4- and 9-hydroxylactams. The rate of disappearance of CR in liver perfusates was slower than in vivo. Bile contained only small amounts of sulphate conjugates and significant amounts of conjugated 2-amino-2'-hydroxymethyldiphenyl ether (amino alcohol). This was not identified in the urine or blood of rats. Preliminary studies in rhesus monkey and the guinea-pig show similar excretory patterns and metabolites. However, only free hydroxylactams were isolated from monkey urine and traces of the amino alcohol were detected in guinea-pig urine. Whole-body autoradiography of mice confirm the rapid disappearance of CR from blood into heart, liver, kidneys and small intestine with evidence of biliary excretion. It is consistent with the rat studies showing the rapid absorption of a highly lipophilic compound undergoing hepatic metabolism, biliary secretion, enterohepatic recirculation and renal excretion.     

The effects of exposure to diazepam during various stages of gestation or during lactation on the development and behavior of rat pups

In the present study we have investigated the effects of diazepam (DZP) (10 mg/kg) treatment of rat dams during different periods of gestation or during lactation on the development and behavior of their offspring. The results show that DZP exposure during different phases of early development has differing effects on later behavior. Exposure during mid-gestation resulted in early and transient hyperactivity, but no learning or memory deficits at 2 months of age were observed. However, both late prenatal and early postnatal exposure to DZP resulted in significant behavioral changes. Late prenatal treatment caused no hyperactivity but resulted in poor performance on the learning and retention of a choice discrimination task, while early postnatal exposure resulted in consistent and lasting hyperactivity and in substantial discrimination learning and retention deficits at 2 months of age.     

Comprehensive observational assessment: Ia. A systematic,quantitative procedure for assessing the behavioral and physiologic state of the mouse

Summary A systematic observational method is described for comprehensively assessing and quantifying the behavioral and physiologic state of the mouse and its response to drugs. With this method, the pattern profile of various classes of pharmacologic agents and their members can be identified and differentiated, and the relative specificity of their actions defined. The method is applicable to a wide range of investigative goals. Inter- and intra-observer reliability studies have shown it to meet the pragmatic requirements for research.The procedure was developed initially at Schering Corp., Bloomfield, N. J. Its further development and revision was supported by grant No. MH 10990 of the National Institutes of Mental Health.     

The discovery of the selective I(f) current inhibitor ivabradine. A new therapeutic approach to ischemic heart disease.

Coronary artery disease is still a major cause of morbidity and mortality in the industrialized countries, despite the advances in pharmacological treatments, risk factor control and the beneficial effect of myocardial revascularization procedures. Medical anti-ischemic treatment is still essential in most patients, but should be improved in terms of efficacy and tolerance to ensure better prevention of mortality and improvement of the quality of life and symptom control. Since increased heart rate plays a major role in coronary artery disease, not only as a trigger of most of the ischemic episodes but also as an independent predictor of mortality, inhibition of the pacemaker I(f) current to induce a direct and selective decrease in heart rate represents an attractive therapeutic approach for coronary artery disease. The screening of original benzocycloalkane compounds, at Servier Research Institute, has led to the selection of ivabradine for clinical development. Preclinical data showed that ivabradine inhibits the I(f) current of the sinus node, induces a selective reduction in heart rate, both at rest and during exercise, preserves myocardial contractility, atrio-ventricular conduction and ventricular repolarization. Ivabradine prevents exercise-induced myocardial ischemia as effectively as a beta-blocker while offering better protection of regional myocardial contractility. These data have been confirmed in humans, and in particular, the anti-ischemic efficacy of ivabradine, at least as effective as a beta-blocker, in patients with stable angina. Large ongoing clinical trials aim to assess the therapeutic value of ivabradine to improve the prognosis of patients with stable coronary disease and left ventricular systolic dysfunction by reducing mortality and the occurrence of major cardiovascular events.