Liposome encapsulation prolongs alfentanil spinal analgesia and alters systemic redistribution in the rat.
(49/188)
The effect of liposome encapsulation on the analgesia produced by intrathecally administered alfentanil was examined in the rat. In rats prepared with chronic intrathecal catheters, alfentanil in doses of 1-50 micrograms was administered intrathecally in either saline or in multilamellar liposomes (dipalmitoylphosphatidylcholine and cholesterol). Animals were then tested for analgesia by hot-plate and paw-pressure tests. A second group of animals received intrathecal injections of 30 micrograms alfentanil in saline or liposomes, and blood samples were obtained at 5, 15, 45, and 135 min thereafter for measurement of alfentanil plasma concentrations. The liposome preparation markedly prolonged spinal analgesia in the paw-pressure test and to a lesser extent in the hot-plate test. Neither the time to peak analgesia nor the intensity of analgesia differed between the saline and liposome groups. Liposome encapsulation significantly reduced the peak alfentanil plasma concentration at 5 min and prolonged the period in which low but measurable levels of alfentanil could be measured in plasma. These pharmacokinetic data demonstrate that liposome encapsulation resulted in a slow but prolonged appearance of free alfentanil into a diffusible pool available for uptake into the spinal cord. Consistent with the lower peak plasma concentration of alfentanil, the liposome group demonstrated a significantly lower incidence of catalepsy, indicating less systemic redistribution of alfentanil to supraspinal sites. Liposome encapsulation thus appears to produce a significant reduction in peak plasma concentration with a concomitant reduction in systemic side effects and an increase in the duration of action for a given intrathecal dose of the otherwise rapidly cleared alfentanil. (+info)
Potential antipsychotic and extrapyramidal effects of (R,S)-3,4-dicarboxyphenylglycine [(R,S)-3,4-DCPG], a mixed AMPA antagonist/mGluR8 agonist.
(50/188)
An involvement of glutamatergic transmission in schizophrenia has been postulated for several years. According to that view, hypofunction of NMDA receptors and a compensatory increase in glutamate release which overstimulates non-NMDA receptors contributes to psychotic symptoms. Therefore, potential antipsychotic drugs are searched for among compounds which block AMPA receptors and inhibit glutamate release. (R,S)-3,4-dicarboxyphenylglycine [(R,S)-3,4-DCPG] is a mixed antagonist of AMPA receptors and agonist of an autoreceptor, i.e. metabotropic glutamate receptor 8. The aim of the study was to look for putative antipsychotic properties of (R,S)-3,4-DCPG in the model of locomotor stimulation induced by amphetamine or phencyclidine in mice. Moreover, a risk of extrapyramidal side-effects induced by this compound was examined, as capability to induce catalepsy in the bar test and to increase the proenkephalin mRNA expression, measured autoradiographically in striatal slices by in situ hybridization. (R,S)-3,4-DCPG (80 mg/kg i.p.) decreased the amphetamine (2.5 mg/kg s.c.)-but not phencyclidine (3 mg/kg s.c.)-induced hyperactivity. That dose of (R,S)-3,4-DCPG did not decrease the spontaneous locomotor activity of mice. However, a dose of 100 mg/kg ip of that compound evoked catalepsy and enhanced the catalepsy and striatal proenkephalin mRNA expression induced by haloperidol (1-2 mg/kg i.p.). The study seems to suggest that (R,S)-3,4-DCPG may possess antipsychotic properties at doses close to those evoking extrapyramidal side-effects which speaks for its rather typical than atypical neuroleptic profile. (+info)
Developmental exposure to 4-hydroxy-2,3,3',4',5-pentachlorobiphenyl (4-OH-CB107): long-term effects on brain development, behavior, and brain stem auditory evoked potentials in rats.
(51/188)
In the present study the developmental neurotoxic effects of the PCB metabolite 4-OH-2,3,3',4',5-pentachlorobiphenyl (4-OH-CB107) were compared with effects caused by a mixture of parent polychlorinated biphenyl (PCB) congeners (Aroclor 1254). Pregnant female Wistar rats were exposed to 0.5 or 5 mg 4-OH-CB107, or 25 mg Aroclor 1254 per kg body weight from gestation days 10 to 16. Plasma thyroid hormone levels were significantly decreased in the offspring of all treatment groups at postnatal day 4 (PND 4). Behavioral experiments using an open field paradigm revealed an impaired habituation in male offspring of all treatment groups at PND 130. Passive avoidance experiments indicated significant influences on the time course of step-down latencies across trials in exposed male rats. Catalepsy induced by haloperidol showed increases in latencies to movement onset in female offspring exposed to 0.5 mg 4-OH-CB107 compared to Aroclor 1254 treated offspring at PND 168-175. Male offspring exposed to 4-OH-CB107 or Aroclor 1254 showed decreases in latencies compared to control animals. Brain stem auditory evoked potentials (BAEPs) measured at PND 300-310 showed significant increases in auditory thresholds in the low frequency range between Aroclor 1254 and 4-OH-CB107 (5 mg/kg bw) treated animals. Measurements of neurotransmitter levels revealed effects of Aroclor 154 exposure on both the dopaminergic and the serotonergic systems, whereas 4-OH-CB107 exposure affected dopaminergic and noradrenergic systems, with slight but not significant effects on the serotonergic system. These results indicate that 4-OH-CB107 is able to induce long-term effects on behavior and neurodevelopment. The observed effects for 4-OH-CB107 are similar to, but in some aspects different from, the effects observed after Aroclor 1254 exposure. (+info)
Neurotensin receptor antagonist SR 142948A alters Fos expression and extrapyramidal side effect profile of typical and atypical antipsychotic drugs.
(52/188)
Antipsychotic drugs (APDs) have previously been shown to alter Fos expression in a regionally specific manner. Increases in Fos expression in the nucleus accumbens (NAcc) are common to all clinically effective APDs. In contrast, APD-induced Fos expression increases in the caudate-putamen (CPu) and prefrontal cortex (PFC) are associated with the extrapyramidal side effect liability of typical APDs or the effectiveness against negative symptoms of atypical APDs, respectively. Considerable evidence suggests that the neuropeptide neurotensin (NT) mediates some of the effects of APDs. To determine whether NT neurotransmission is also involved in APD-induced Fos expression in brain regions relevant for therapeutic efficacy, the NT receptor antagonist SR 142948A (10 or 100 microg/kg i.p.) was coadministered with APDs (haloperidol (2.0 mg/kg s.c.), olanzapine (5 mg/kg i.p.), or clozapine (20 mg/kg s.c.)). Fos expression was evaluated in the PFC, NAcc shell, dorsomedial, and dorsolateral CPu and the lateral septum. SR 142948A attenuated haloperidol-induced Fos expression in the CPu but, in contrast, increased olanzapine-induced Fos expression in this brain region. The effects of the NT receptor antagonist were paralleled by its effects on catalepsy in olanzapine--but not haloperidol--treated animals. (+info)
Narcolepsy in Singapore: is it an elusive disease?
(53/188)
INTRODUCTION: The aims of the study were to determine the demographic, clinical, and polysomnographic characteristics of narcolepsy, and to address the difficulties in diagnosing narcolepsy and cataplexy, which is a cardinal symptom. We also ventured to investigate the differences between narcolepsy with and without cataplexy. MATERIALS AND METHODS: Data were collected retrospectively from patients diagnosed with narcolepsy at the Sleep Disorder Unit of Singapore General Hospital over 5 years. Each patient had had a detailed clinical evaluation and overnight polysomnography (PSG) followed by a multiple sleep latency test (MSLT). RESULTS: A total of 28 cases were studied. Males made up 85.7% of the total and females, 14.3%. The mean age was 30.9 years. All had excessive daytime sleepiness. Other manifestations were cataplexy (48.1%), sleep paralysis (51.9%), hypnogogic hallucinations (84%), disturbed night sleep (29.2%), automatisms (17.4%) and catnaps (95.8%). The mean duration of symptoms was 7.24 years. In the MSLT, the mean values for mean sleep latency and number of sleep onset rapid eye movement (REM) periods (SOREMP) were 4.3 minutes and 2.7, respectively. Narcolepsy was associated with obstructive sleep apnoea and periodic limb movement disorder (35.7%). All the variables were compared between those who had narcolepsy with cataplexy and without cataplexy. The duration of presenting complaint, REM latency, respiratory disturbance index, number of SOREMPs and the presence of sleep paralysis were significantly different in the 2 groups. CONCLUSIONS: Narcolepsy predominantly affects young males. Concurrence of other sleep disorders is not uncommon. Some differences are evident between those who have narcolepsy with and without cataplexy. (+info)
Delta9-tetrahydrocannbinol accounts for the antinociceptive, hypothermic, and cataleptic effects of marijuana in mice.
(54/188)
Although it is widely accepted that delta9-tetrahydrocannabinol (delta9-THC) is the primary psychoactive constituent of marijuana, questions persist as to whether other components contribute to marijuana's pharmacological activity. The present experiments assessed the cannabinoid activity of marijuana smoke exposure in mice and tested the hypothesis that delta9-THC mediates these effects through a CB1 receptor mechanism of action. First, the effects of delta9-THC on analgesia, hypothermia, and catalepsy were compared with those of a marijuana extract with equated delta9-THC content after either i.v. administration or inhalation exposure. Second, mice were exposed to smoke of an ethanol-extracted placebo plant material or low-grade marijuana (with minimal delta9-THC but similar levels of other cannabinoids) that were impregnated with varying quantities of delta9-THC. To assess doses, delta9-THC levels in the blood and brains of drug-exposed mice were determined following both i.v. and inhalation routes of administration. Both marijuana and delta9-THC produced comparable levels of antinociception, hypothermia, and catalepsy regardless of the route of administration, and these effects were blocked by pretreatment with the CB1 antagonist SR141716 [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazol e-3-carboxamide HCl]. Importantly, the blood and brain levels of delta9-THC were similar in mice exhibiting similar pharmacological effects, regardless of the presence of non-delta9-THC marijuana constituents. The present experiments provide evidence that the acute cannabinoid effects of marijuana smoke exposure on analgesia, hypothermia, and catalepsy in mice result from delta9-THC content acting at CB1 receptors and that the non-delta9-THC constituents of marijuana (at concentrations relevant to those typically consumed) influence these effects only minimally, if at all. (+info)
Elucidation of dose-effect relationships for different opiate effects using alfentanil in the spontaneously ventilating rat.
(55/188)
In addition to producing antinociception and mild sedation, opiates diminish spontaneous movement and produce muscle rigidity. Examination of the relationship between different opiate effects may lead to a better understanding of the mechanism and sites of action of opiate anesthesia. Previous studies have compared the dose-effect relationships for morphine and fentanyl between antinociception and loss of righting reflex. However, neither muscle rigidity nor lack of spontaneous movement (as measured by catalepsy) has been fully examined or directly compared with either antinociception or loss of righting reflex. This study, therefore, compared five clinically relevant opiate endpoints (antinociception, muscle rigidity, catalepsy, loss of righting reflex, and respiratory depression) using the mu-selective agonist alfentanil in the spontaneously ventilating rat. Rats were randomized to receive alfentanil (0-500 micrograms/kg) subcutaneously. For muscle rigidity, 59 rats had electromyographic activity measured with percutaneous hindlimb electrodes. After alfentanil injection, electromyographic data were recorded for 60 min. For antinociception and catalepsy, 49 rats were studied for 120 min after alfentanil. Catalepsy was measured from the time the rat's forelimbs were placed on a 10-cm-high bar until either limb was removed. Antinociception was studied by measuring tail-flick response to hot (55 degrees C) water. For righting reflex, 40 rats were studied for 120 min. Alfentanil-induced respiratory depression was assessed in 40 rats with indwelling tail arterial catheters. Alfentanil was administered after baseline arterial blood gas measurements, and then additional samples were obtained for 45 min. For each effect, data were converted into quantal responses and were then transformed to probit-log dose-response curves for analysis.(ABSTRACT TRUNCATED AT 250 WORDS) (+info)
Neuroleptic-induced catalepsy: electrophysiological mechanisms of functional recovery induced by high-frequency stimulation of the subthalamic nucleus.
(56/188)
High-frequency stimulation (HFS) of the subthalamic nucleus (STN) remarkably alleviates motor disorders in parkinsonian patients. The mechanisms by which STN HFS exerts its beneficial effects were investigated in anesthetized rats, using a model of acute interruption of dopaminergic transmission. Combined systemic injections of SCH-23390 [R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5,-tetrahydro-1H-3-benzazepine] and raclopride, antagonists of the D1 and D2 classes of dopaminergic receptors, respectively, were performed, and the parameters of STN HFS that reversed the neuroleptic-induced catalepsy were determined in freely moving animals. The effects of neuroleptics and the impact of STN HFS applied at parameters alleviating neuroleptic-induced catalepsy were analyzed in the substantia nigra pars reticulata (SNR), a major basal ganglia output structure, by recording the neuronal firing pattern and the responses evoked by cortical stimulation. Neuroleptic injection altered the tonic and regular mode of discharge of SNR neurons, most of them becoming irregular with bursts of spikes and pauses. The inhibitory component of the cortically evoked response, which is attributable to the activation of the direct striatonigral circuit, was decreased, whereas the late excitatory response resulting from the indirect striato-pallido-subthalamo-nigral circuit was reinforced. During STN HFS, the spontaneous firing of SNR cells was either increased or decreased with a global enhancement of the firing rate in the overall population of SNR cells recorded. However, in all of the cases, SNR firing pattern was regularized, and the bias between the trans-striatal and trans-subthalamic circuits was reversed. By these effects, STN HFS restores the functional properties of the circuits by which basal ganglia contribute to motor activity. (+info)