A. Wauquier

Photochemical stroke model: flunarizine prevents sensorimotor deficits after neocortical infarcts in rats.

We produced unilateral photochemical infarcts in the hindlimb sensorimotor neocortex of 186 rats by intravenous injection of the fluorescein derivative rose bengal and focal illumination of the intact skull surface. Infarcted rats showed specific, long-lasting deficits in tactile and proprioceptive placing reactions of the contralateral limbs, mostly the hindlimb. Placing deficits were most prominent during transition to immobility and/or when independent limb movements were required. Administration of flunarizine, a Class IV calcium antagonist, 30 minutes after infarction resulted in marked sparing of sensorimotor function in 30 rats. In contrast to 20 vehicle-treated rats, which remained deficient for at least 21 days, 15 (75%) of the rats treated with 1.25 mg/kg i.v. flunarizine showed normal placing on Day 1 after infarction, whereas the remaining five (25%) recovered within 5 days. Oral treatment of 10 rats with 40 mg/kg flunarizine was also effective. Neocortical infarct volume and thalamic gliosis, assessed 21 days after infarction, did not differ between 30 flunarizine- and 30 vehicle-treated rats. However, when 4-hour-old infarcts were measured in 16 rats, posttreatment with intravenous flunarizine reduced infarct size by 31%. In combination with appropriate behavioral analyses, photochemical thrombosis may constitute a relevant stroke model, in which flunarizine preserved behavioral function during a critical period, corresponding to the spread of ischemic damage.

Evidence for a role of the N-methyl-d-aspartate (NMDA) receptor in cortical spreading depression in the rat

The neurotransmitter glutamate activates the N-methyl-D-aspartate (NMDA), quisqualate and kainate receptors. It has been proposed, but also disputed, that local release of glutamate would play a pivotal role in cortical spreading depression (SD). We tested this hypothesis by investigating the influence of NMDA antagonists on SD, using the non-competitive NMDA antagonists ketamine, phencyclidine (PCP) and MK-801 and the competitive NMDA antagonist DL-2-amino-7-phosphonoheptanoate (2-APH), injected intraperitoneally in rats anesthetized with alfentanil. SD was elicited by cathodal DC-stimulation of the frontal cortex. SD propagation was followed using two ion-sensitive microelectrodes placed in the parietal and occipital cortex. The NMDA antagonists increased SD threshold, decreased the propagation velocity and decreased the duration of the accompanying extracellular DC, K+ and Ca2+ changes at the following doses: 40 mg/kg ketamine, 10 mg/kg PCP, 0.63 mg/kg MK-801, 10 and 40 mg/kg 2-APH. With each NMDA antagonist failure of SD propagation between both microelectrodes could be observed. SD elicitation (or propagation) was inhibited completely with 80 mg/kg ketamine, 3.1 mg/kg MK-801 and 160 mg/kg 2-APH. These NMDA antagonists have also anticonvulsant properties. None of these effects on SD were observed with high doses of other anticonvulsants such as 80 mg/kg phenytoin or 40 mg/kg diazepam. These experiments indicate that endogenous release of excitatory amino acids and their action on the NMDA receptor play an important role in the initiation, propagation and duration of SD.

Functional role of 5-HT2 receptors in the regulation of sleep and wakefulness in the rat

Recently developed agents specifically acting on different 5-hydroxytryptamine (5-HT) receptor populations were used to analyze the functional role of 5-HT2 receptor subtypes in the sleep-wakefulness cycle of the rat. The 5-HT2 receptor antagonist ritanserin injected intraperitoneally (IP) (0.04–2.5 mg/kg) induced an increase in deep slow wave sleep (SWS2) duration at the expense of wakefulness (W), light slow wave sleep (SWS1) and paradoxical sleep (PS). The stimulation of 5-HT2 receptors by 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) produced a dose-related increase in W and a dose-dependent decrease in both SWS2 and PS. Pretreatment with ritanserin (0.16–2.5 mg/kg) or with cinanserin (2.5–5 mg/kg), another 5-HT2 receptor antagonist, dose-dependently reversed the W enhancement and the SWS2 deficit produced by DOM, but not the PS deficit. Sleep-wakefulness alterations (increase in W and SWS1 combined with a suppression of SWS2 and PS) observed after IP injection of two putative 5-HT1 receptor agonists, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) (2.5 mg/kg) and 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole (RU 24969) (0.63 mg/kg), were not modified by ritanserin pretreatment (0.16–2.5 mg/kg). These results further support the hypothesis that the serotonergic system plays an active role in the regulation of the sleep-wakefulness cycle in the rat and that 5-HT2 receptors are involved in this action. In addition it is suggested that 5-HT1 receptor subtypes are unlikely to interact with 5-HT2 receptors in the sleep-wakefulness modulation mediated through 5-HT2 receptors.

Double-Blind Placebo-Controlled Trial of Flunarizine as Add-on Therapy in Epilepsy

Summary: In a therapy‐resistant epileptic population with partial complex seizures with or without secondary generalization, addition of flunarizine to existing therapy was accompanied by a significant reduction in complex partial and tonic‐clonic seizures. This result did not appear to be due to serial effects or changes in the plasma levels of the co‐medication. Side effects were rare. The serum flunarizine levels (13.8 ng/ml; range, 3–32.5 ng/ml) were lower than previously reported on a daily dose of 10 mg. This may reflect increased metabolism due to induction of liver enzymes by the co‐medication. Given this finding, together with the low incidence of side effects, a further study is required to determine whether higher blood levels would give an improved degree and incidence of seizure reduction.

Behavioral analysis of the effects of 15 anticonvulsants in the amygdaloid kindled rat.

One hundred-four Wistar rats were implanted with a bipolar electrode aimed at the right basolateral amygdala, and stimulated bipolarly twice daily (interval between stimulations 30 min) with a 150 μA, 4-s train of biphasic square-wave 1-ms pulses (100 pulses/s). Seventy-four animals developed a stimulation-induced clonic convulsion and, after further testing, 41 animals satisfied the stability criteria for entrance into the drug study. These criteria were three convulsions in response to three stimulations on the tenth stimulation day, and a convulsion after each stimulation for a period of 1 week on the drug-testing schedule. In the standardized test system, kindled rats were given two control stimulations; drug was then administered IP and, 30 min and 24 h later, further stimulation was given. After each stimulation the presence or absence of ipsilateral turning, closing of the ipsilateral eye, rearing up, falling over, facial clonus, forepaw clonus, hind paw clonus, hind paw tonus, and wet-shaking was assessed and the duration of forepaw clonus was measured. ID50 values (mg/kg) for inhibition of forepaw clonus 30 min after injection are: Clonazepam, 0.28; diazepam, 0.28; chlordiazepoxide, 0.86; carbamazepine, 5.0; meprobamate, 11.2; mesuximide, 17.5; depamide, 22.4; diphenylhydantoin, 31.5; phenacemide, 31.6; flunarizine, 42.8; mephenytoin, 64.7; valproate sodium, 64.7; acetazolamide, 80.0; trimethadione, 120.0; and primidone, 142.2. The ED50 doses for inhibition of the other seizure components were significantly correlated (P<0.01) with their ID50 value for forepaw clonus. These results suggest that the kindled rat is an appropriate and sensitive model with which to assess anticonvulsant drugs.

Effects of ritanserin on sleep disturbances of dysthymic patients

Ritanserin, a selective and potent serotonin-2 antagonist, is effective in the treatment of a variety of syndromes related to anxiety and depression, including dysthymic disorder. In animals and healthy volunteers, ritanserin specifically increases slow-wave sleep and the hypothesis arises that this effect on sleep may contribute to its therapeutic properties. Therefore, we studied the effects of ritanserin on sleep in a group of dysthymic patients (DSM-III). Polygraphic recording as well as subjective evaluations of the quality of sleep were performed before and at the end of a 4-week period of double-blind medication with either ritanserin (10 mg o.d. in the morning) or placebo. At baseline, patients showed at fragmented and superficial sleep, with low amounts of slow wave sleep. Ritanserin significantly increased Slow Wave Sleep and changed the frequency and distribution of some stage transitions during the night. No other sleep parameters were modified by ritanserin treatment.

Neuroleptics and Brain Self-Stimulation Behavior

Publisher Summary Pharmacological studies on self-stimulation and neurochemical identification of the involved pathways gave rise to the catecholamine hypothesis of self-stimulation behavior. According to this hypothesis, the effects of electrical self-stimulation are mediated by noradrenergic and dopaminergic neuronal pathways. However, it is shown that self-stimulation behavior can also be induced by applying electrical stimulation to non-aminergic structures. There are a variety of neuroleptics belonging to different chemical classes—namely, the rauwolfia alkaloids (reserpine-like), the phenothiazines (chlorpromazine-like), the butyrophenones (haloperidol-like), and the diphenylbutylamines (pimozide-like). Particular attention is directed towards neuroleptics that effectively control psychotic symptoms, reduce relapse, and enable patients to be reintegrated into society. The differential inhibition suggests that the neuroleptic inhibitory property depends on the strength of the stimulation. Within a given structure, different response rates are obtained by varying the stimulus parameter combinations (SPCs) and possibly reflect a different rewarding or discriminating level. The neuroleptics are compared based on different pharmacological tests, and appropriate methods make it possible to integrate the self-stimulation test within the results of other pharmacological experiments.

Behavioral analysis of amygdaloid kindling in beagle dogs and the effects of clonazepam, diazepam, phenobarbital, diphenylhydantoin, and flunarizine on seizure manifestation.

Abstract This paper describes the behavioral changes seen in beagle dogs during kindling and reports on the effects of clonazepam, diazepam, phenobarbital, diphenylhy-dantoin, and flunarizine on kindled seizures. Eight dogs were implanted stereotaxically in the right basolateral amygdala. After recovery, they were stimulated once daily at stimulation parameters evoking mastication in the first sessions. Generalized tonic-clonic seizures developed rapidly in all dogs with an intermediate stage of facial clonus, head nodding, and profuse salivation. Kindled seizures began with facial clonus, head nodding, and salivation, and were followed by opisthotonos, lifting of the contralateral forepaw, falling over backward, clonicity of the hind legs, tonic extension of the forelegs and hindlegs, quiescence, myoclonic jerking or running seizures; and terminated with wetshaking. Diazepam (2.5 mg/kg) and phenobarbital (10 mg/kg) inhibited all phenomena in all animals. Clonazepam (≥0.63 mg/kg) and flunarizine (≥5 mg/kg) protected two of three animals against tonic and clonic seizures, but clonazepam was ineffective against facial clonus. Diphenylhydantoin was ineffective at doses to 40 mg/kg. Spontaneous seizures were seen occasionally in all animals. Four dogs died after developing status epilepticus. Kindling in dogs occurred rapidly and did not show the five stages seen in rats, and when kindled, animals were susceptible to the development of spontaneous seizures and status epilepticus.

Open dose-ranging trial of flunarizine as add-on therapy in epilepsy.

Summary: A double‐blind placebo‐controlled crossover trial of flunarizine as add‐on treatment in therapy‐resistant epilepsy offered significant evidence of efficacy, but the plasma levels of flunarizine were lower than anticipated, probably due to induction of liver enzymes by comedication. An open dose‐ranging trial was therefore undertaken to investigate the relationships among dose, efficacy, side effects, and blood level. With basal medication held constant, flunarizine was added at 3‐month intervals in increasing doses of 0, 10, 15, 20, and 25 mg daily, or until side effects occurred or marked seizure reduction was obtained. Forty‐seven patients completed the trial; all were adults with therapy‐resistant epilepsy who had at least 3 seizures per month. All had complex partial seizures, with additional types in 20. Sixteen patients showed a 50% and 24 a 25% reduction of seizure incidence on flunarizine; 6 and 7, respectively, showed a corresponding increase. The greatest seizure reduction, when observed, occurred generally at a daily dose of 15–20 mg. Side effects, chiefly drowsiness and weight gain, increased markedly between 15 and 20 mg daily. Flunarizine administration produced no change in serum levels of comedication, but flunarizine levels were lower in patients taking more than one other drug. Seizure reduction was obtained most consistently in patients with secondary generalized epilepsy or neurologic deficits. The findings confirm the antiepileptic action of flunarizine in humans and justify further trials.

Differential antagonism by naloxone of inhibitory effects of haloperidol and morphine on brain self-stimulation.

Haloperidol (0.16 mg/kg) or morphine sulfate (40 mg/kg), injected subcutaneously, completely suppressed bar-pressing for brain self-stimulation in rats implanted with electrodes in the lateral hypothalamus. Haloperidol also caused catalepsy and ptosis while morphine produced catatonia with exophthalmia. Naloxone in a dose (5 mg/kg) which was ineffective when given alone, differentially reversed the morphine-effects but was without any reversing influence on the actions of haloperidol.