Diazepam--morphine hypnotic synergism in rats.

The effect of diazepam-morphine combination on the righting reflex was studied in rats. Doses of the drugs given alone and in combination that block righting reflex (RR ED50) were determined with a probit procedure. Brain concentrations following equieffective doses of the drugs administered separately and in combination were determined by radioimmunoassay. Equieffective intravenous doses and corresponding brain concentrations for the agents were compared with fractional (algebraic) and isobolographic analyses. Interaction between diazepam and morphine was found to be synergistic. It is not likely to be pharmacokinetic in nature.

Disability profiles and objective quantitative assessment in Parkinson's disease.

A new technique for quick objective and quantitative determination of important aspects of the motor handicap in movement disorders is presented. A compound, but natural, test movement was used to find out if the degree of dysfunction in postural, locomotor and manual motor functions differed among the patients and if medication influenced these functions differently. After 12 h without medication, 16 patients with Parkinson's disease showed a movement time between 1.5 and 13.6 times that of an age-matched normal subject and a greater performance variability on repeated examination. In some patients the increase of test movement time was caused mainly by the locomotion component while in others the time for the postural or manual part of the movement was more markedly augmented. Thus, a specific motor disability profile was found for each patient and expressed in quantitative terms. The effects of l-dopa treatment were quantified in each patient.

Posture in Parkinson's disease: impairment of reflexes and programming.

The leg muscle electromyographic responses induced during stance by impulsive displacements of a treadmill belt (directed forward or backward and at different rates) were studied in a group of patients with Parkinson's disease and a group of age-matched healthy subjects. Young normal subjects were also studied both before and after intake of a dopamine antagonist (haloperidol). Compensatory gastrocnemius electromyographic responses resulting from backward-directed displacements were significantly smaller in both the patients and the young normal subjects following intake of haloperidol. The reduced sensitivity of the gastrocnemius muscle to stretch correlated with an inability to compensate for the perturbations. In the patients, the gastrocnemius response was followed by enhanced activation of the tibialis anterior muscle. This was not the case in the normal subjects after intake of dopamine antagonist and is probably not, therefore, the consequence of acute dopamine deficiency. In the patients the angular rotation at the ankle joint induced during faster backward-directed displacements was slower than that in normal subjects, despite identical amounts of gastrocnemius electromyographic activity. This supports earlier findings of changes in intrinsic muscle stiffness in Parkinson's disease. None of these differences were seen when the tibialis anterior muscle was stretched. This differential behavior of the antagonist leg muscles can best be explained by the different function fulfilled by these muscles in regulation of stance and gait.

Abnormal gait sequence in locomotion after atropine treatment of catecholamine-deficient akinetic rats.

Excessive, abnormal locomotion occurs after a high dose (25-50 mg/kg) of atropine sulfate to rats already akinetic due to catecholamine deficiency from intraventricular administration of 6-hydroxydopamine. This abnormal locomotion involves an abnormal gait sequence [right (R) hindleg (H), left (L) foreleg (F), LH, RF] instead of the normal gait sequence (RH, RF, LH, LF). In such animals atropine progressively (i) decreases hindleg step size, (ii) decreases arching of the trunk, and (iii) increases foreleg step size. These factors combine to change the ratio of front/hind body support. If the body stretches too far and the hindleg step is too small, a given hindleg step supports insufficient weight to remove weight from the ipsilateral foreleg; consequently, the opposite foreleg must execute the next step, producing the abnormal gait sequence. Thus, atropine affects gait sequence indirectly; it acts on at least three variables that affect how body weight is distributed and shifted during locomotion. To maintain stability during such locomotion, gait sequence is appropriately altered.

Morphine and fentanyl hypnotic interactions with thiopental.

The effects of morphine-thiopental and fentanyl-thiopental combinations on the righting reflex were studied in rats. Doses that block the righting reflex for the agents given alone and for their combinations were determined with a probit procedure and compared with an isobolographic analysis. Interaction between morphine or fentanyl and thiopental on blockade of the righting reflex were both found to be synergistic. The degree of synergism was relatively small for the fentanyl-thiopental combination; the maximal deviation from additive interaction (expected/observed ratio) for ED50 dose level was 1.15 (P less than 0.01). The degree of synergism was greater for the morphine-thiopental combination; the maximal deviation from additive interaction was 2.27 (P less than 0.001). Comparison of the results with the outcomes of opioid-barbiturate interactions in relation to blockade of purposeful movement response to tail clamping, which was antagonistic, shows that the combination of a barbiturate with an opioid gives different outcomes for different end-points of anesthesia. This suggests that the anesthetic effect of an agent is composed of several components, each with a different mechanism of action.

Lisuride inhibits temporarily sexual behavior in female rats.

The effect of lisuride (0.1 and 0.2 mg/kg IP) on the sexual behavior was studied in the adult, ovariectomized and chronically estradiol-primed female rats. The behavioral tests were done under dyadic interaction with males 60 min before and 30, 120 and 360 min after lisuride or saline injection. Lisuride induced a prompt, short-termed and dose-dependent loss of the precopulatory patterns (darting, hopping, presenting posture) while the effect on the copulatory (lordosis) behavior was weaker. A partial restoration of the precopulatory behavior was observed in the 120th min, the full restoration of the original precopulatory states was found in the 360th min. The inhibitory effect of lisuride on feminine sexual behavior is in contrast with its facilitatory effect on masculine sexual behavior in rats. The results suggest that the serotonergic system participates in the mediation of both copulatory (receptive) behavior and precopulatory (proceptive) behavioral patterns.

Antagonism of sexual behavior in female rats by ventromedial hypothalamic implants of antiestrogen.

The present experiments sought to identify brain regions in which implants of an antiestrogen would antagonize the ability of a systemic estradiol treatment to activate sexual behavior in female rats. In experiment 1, ovariectomized female rats were implanted subcutaneously with 5-mm Silastic capsules containing a 5% concentration of estradiol and injected with 500 micrograms progesterone 2 days later, 4-5 h before testing for sexual behavior. Bilateral intracranial implants of 1% crystalline concentrations of the high-affinity antiestrogens monohydroxytamoxifen (TAM) or keoxifene placed into the ventromedial nucleus of the hypothalamus (VM) 24 h prior to estradiol treatment significantly reduced lordosis responsivity compared with control females receiving empty cannulae. Implants of 1% TAM into the medial preoptic area or medial amygdala 24 h prior to estradiol that no significant effect on lordosis. Similarly, implants of 1% TAM into the VM 12 h after estradiol had no effect on lordosis. In experiment 2, lordosis was activated by subcutaneous implants of Silastic capsules containing 1% estradiol plus 500 micrograms progesterone. In this experiment, implants of 1% TAM into the VM 24 h prior to estradiol significantly reduced lordosis only if both cannulae tips were in, or adjacent to, the VM. Females receiving intracranial 1% TAM, but whose cannulae (even unilaterally) were outside the VM, had levels of lordosis equivalent to those of control females. Increasing the concentration of intracranial TAM to 10% virtually eliminated lordosis in females with bilateral implants in the VM, whereas females receiving intracranial 10% TAM in the region of, but outside, the VM showed no evidence of a lordosis deficit.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of turning by direct intrastriatal injection of dopaminomimetic drugs in mice: pharmacological analysis of a simple screening model.

A new simple model designed for the screening of dopaminomimetic drugs in mice is presented. When injected directly into the right striatum of conscious mice, the dopamine (DA) receptor agonists apomorphine, SKF 38393 and bromocryptine, the indirect DAmimetic drugs (+)-amphetamine and nomifensine, the atypical DAergic antidepressant drug minaprine, induced contralateral rotations. Rotations induced by DA mimetics were antagonized by i.p. injected haloperidol. A pretreatment with the D1 antagonist SCH 23390 (s.c.) antagonized the turning induced by apomorphine or by the D1 agonist SKF 38393, and, to a lesser extent, that induced by the D2 agonist bromocryptine. In contrast, the D2 antagonist (-)-sulpiride (i.p.) blocked the effects of the 3 agonists to the same extent. A pretreatment with alpha-methylparatyrosine (i.p.) antagonized rotations induced by bromocryptine, (+)-amphetamine and minaprine, but not those induced by nomifensine or apomorphine. The results suggest that this model could represent a useful screening tool for the search of new DAmimetic drugs, and for the assessment of DA receptor blockade.

Prenatal benzodiazepine effects in mice: postnatal behavioral development, response to drug challenges, and adult discrimination learning.

Oxazepam treatment of primiparous mouse dams on days 12-16 of pregnancy (15 mg/kg p.o. twice daily) produced a transient retardation of postnatal body growth and neurobehavioral development, a reduction of the hyperactivity response to amphetamine in open-field tests on postnatal days 14-16, and a selective impairment of adult active avoidance in four go-no go discrimination tasks. Equally important for understanding the nature of the prenatal benzodiazepine syndrome were several negative results, namely, the absence of changes in homing performance on postnatal day 10, an intact hyperactivity response to scopolamine on postnatal days 21-23, a lack of effects on adult activity, and a normal passive avoidance performance in the go-no go tasks. A modification in monoaminergic regulatory functions may account for the overall profile of prenatal drug effects. Based on the results of this experiment, of a preliminary multidose study (0-50 mg/kg), and of an additional cross-fostering experiment, several methodological issues are addressed. These include the choice of appropriate treatment schedules and of testing procedures adequate for each developmental stage, and the control for various confounding variables such as litter effects, postnatal maternal influences, and developmental history.

Single dose pharmacokinetics and pharmacodynamics of oral loprazolam in the elderly.

The pharmacokinetics of the benzodiazepine hypnotic, loprazolam (1.0 mg orally), and the pharmacodynamic response to single oral doses (0.5 mg and 1.0 mg) have been compared in young and elderly healthy volunteers. No difference between the groups in peak plasma concentration (Cmax) or in the time to peak (tmax) was found, but the elimination half-life t1/2,z and area under the plasma concentration-time curve (AUC) were significantly greater in the elderly group. The immediate effects of loprazolam on all three performance tests used (postural sway, critical flicker fusion threshold (CFFT) and choice reaction time (CRT] and on subjective sedation tended to be more pronounced in the elderly subjects, though intersubject variability in response was high in both groups. The corresponding plasma concentrations did not differ significantly between the two groups. The higher (1.0 mg) dosage was associated with significant residual (11 h) impairment of standing steadiness in the elderly subjects. No other hangover effects were observed. The results are compatible with previous evidence of increased 'sensitivity' to benzodiazepines in the elderly and suggest that a lower (0.5 mg) starting dose of loprazolam would be appropriate for older recipients. Further investigation would be necessary to establish whether clinically relevant accumulation of loprazolam occurs in the elderly following repeated dosage.

Responsiveness to oral diazepam in the elderly: relationship to total and free plasma concentrations.

The immediate and residual response to single doses of oral diazepam 10 mg was measured in 11 young and 12 elderly healthy volunteers using postural sway, digit symbol substitution scores and subjective ratings. The effect on postural sway was markedly accentuated in the older volunteers, but the difference between groups in the effect on the other measures used did not achieve significance. The corresponding plasma total diazepam concentrations were lower in the older subjects beyond 0.5 h post dose and the concentrations of plasma desmethyldiazepam did not differ between the groups. Diazepam plasma protein binding was significantly reduced in the elderly subjects, but the plasma free (unbound) diazepam concentrations did not exceed those in the young group. There was poor correlation between the responses measured and the concentrations of either total diazepam, desmethyldiazepam or free diazepam. The results suggest the occurrence of a non-uniform effect of age on different aspects of benzodiazepine response, and that where an accentuated effect occurs the mechanisms are substantially pharmacodynamic.

Forelimb placing and hopping reflexes in haloperidol- and morphine-treated cataleptic rats.

Although both haloperidol and morphine produce catalepsy, there are fundamental differences in their neurological effects (De Ryck, Schallert, & Teitelbaum, 1980). Haloperidol-treated rats show brisk righting, bracing, and clinging reflexes, effects suggesting that motor subsystems subserving static postural support are dominant over those involved in more phasic locomotor and orienting movements. In contrast, morphine-treated rats show impaired righting, bracing, and clinging, effects suggesting that postural support mechanisms are suppressed. In order to determine whether phasic postural reactions other than righting are also differentially affected by these drugs, forelimb placing and hopping reflexes were evaluated in rats given either haloperidol (0, 0.25, 0.5, 1, and 5 mg/kg) or morphine sulfate (0, 10, 20, and 40 mg/kg). Morphine produced a dose-dependent impairment in all tests. In contrast, haloperidol did not impair contact placing to dorsal stimulation of the limb or chin placing. Hopping and contact placing to lateral stimulation of the limb were impaired by haloperidol, perhaps because stimulation induced a competing tendency to brace. These results provide additional evidence that morphine and haloperidol produce functionally different neurological states.

Effects of ovariectomy and estrogen replacement on intrastriatal dopamine-elicited postural deviation.

The effects of ovariectomy, sham ovariectomy, and estradiol benzoate replacement on unilateral intrastriatal dopamine-induced postural deviation were studied in rats. Animals were tested prior to surgery, and at both two and seven days after surgery. Relative to the pre-surgery test, ovariectomized rats greatly increased this behavioral response two days after surgery while sham ovariectomy resulted in no significant change. Estradiol benzoate treatment in ovariectomized animals not only prevented this increase but significantly suppressed it at both two and seven days after surgery relative to pre-surgery levels. Thus, removal of endogenous estrogen in female rats resulted in an acute increase in a striatal DA-mediated behavior which could be prevented by hormone replacement. These results are consistent with the hypothesis that estrogen suppresses some striatal DA-mediated behaviors.

Studies in vivo with ICI 174864 and [D-Pen2, D-Pen5]enkephalin.

We studied the in vivo pharmacology of a selective agonist (DPDPE) and a selective antagonist (ICI 174864) at delta opioid receptors. ICI 174864 (10 micrograms icv) caused postural abnormalities, barrel rotation and hypothermia in rats. DPDPE induced behavioural arousal (at 75 micrograms icv) and barrel rotation (at 125 micrograms) in rats. ICI 174864 (10 micrograms icv) attenuated acetic acid induced writhing in mice. This action was antagonized by naloxone (10 but not 2 mg/kg s.c.). A lower, non-agonist dose of ICI 174864 (5 micrograms) antagonized DPDPE (3 micrograms icv) in this test without affecting DAGO (0.0006 micrograms icv), a selective agonist at mu receptors. In the mouse tail flick test, ICI 174864 (10-50 micrograms icv) did not significantly antagonize the agonist actions of DPDPE (40 micrograms icv) or DAGO (0.3 micrograms icv). At 10-50 micrograms icv, ICI 174864 had no marked effect on gastrointestinal transit in mice. ICI 174864 (25 micrograms icv or 20 mg/kg s.c.) did not interact with mu opioid receptors in mice rendered physically dependent on morphine.

Reassessing morphine effects in cats: I. Specific behavioral responses in intact and unilaterally brain-lesioned animals.

Behavioral responses to single low doses of morphine (0.5-3.0 mg/kg IP) were measured in intact cats and in cats with removal of one cerebral hemisphere or one caudate nucleus. Responses were dose-dependent and formed 3 stages: (1) autonomic stage (0-15 min postdrug): with vocalization, salivation, licking, swallowing, retching and vomiting; (2) quiet stage (15-60 min postdrug): sitting, fixed gaze, mydriasis, and pricked pinnae; (3) head movement stage (from 30-60 min postdrug and decreasing by the 5th hr): fully aroused but mostly sitting; showing discrete, complex head movements of a visual-tracking type with pouncing/avoidance paw movements, and with irregular, dose-dependent bouts of rocking, pivoting, and backing. Sleep, grooming, micturition and defecation were suppressed. In hemispherectomized cats the frequency of head movements was increased only towards the side of the ablation, and there was a strong bias for body turning to that side together with a significant bias to move the ispilateral paw. None of these biases were significant in cats with a unilateral caudate ablation. We conclude that the cat is an excellent model for behavioral morphine studies when dose levels below those inducing "feline mania" are used. CNS sites underlying these responses are discussed.

Rotation and postural deviation elicited by microinjections of dopamine into medial and lateral regions of dorsal striatum.

Unilateral microinjections of DA (25 micrograms/0.25 microliter) into several medial to lateral regions of the dorsal striatum of female rats produced both contralateral postural deviation and rotation. However, injections of DA into the medial striatum were more effective in producing rotation than postural deviation, whereas the opposite was the case for lateral striatal injections.

Gamma-aminobutyric acid and basal ganglia outflow pathways.

Neurons containing gamma-aminobutyric acid (GABA) are important outflow pathways from the striatum to the pallidal complex and substantia nigra. From these areas GABA-containing neurons pass to the thalamus and to various areas of the brainstem. Manipulation of GABA function in outflow zones in the rat can produce catalepsy, locomotor hyperactivity, stereotypy or circling behaviour, so mimicking the effect of altered dopamine function within basal ganglia. However, the behaviours produced by such manipulation do not form part of the animal's normal activities. Consequently manipulation of GABA action in the outflow zones of the basal ganglia may mimic extrapyramidal movement disorders more closely than the normal functions of these regions of the brain.