The effects of neuroleptics with central dopamine and noradrenaline receptor blocking properties in the L-DOPA and (+)-amphetamine-induced waking EEG in the rat

1 A study was carried out in rats (prepared for chronic sleep recording) of the effects of pretreatment with neuroleptics differing in their relative antinoradrenaline and antidopamine receptor potencies, on the L-DOPA and (+)-amphetamine-induced increase in waking EEG. 2 Haloperidol (0.6 mg/kg), which blocks central dopamine and noradrenaline (NA) receptors, reversed the EEG desynchronizing actions of L-DOPA and (+)-amphetamine. 3 Low doses of pimozide (0.4 to 0.8 mg/kg) which block dopamine receptors exclusively, were not able to modify the pharmacologically induced disruption of the sleep-awake cycle. However, at 1 mg/kg, a dose which also produces blockade of NA receptors, pimozide counteracted the increase in waking elicited by (+)-amphetamine. 4 Spiroperidol (1 to 4 mg/kg) which is devoided of NA receptor blocking properties, failed to reverse the L-DOPA or (+)-amphetamine-induced arousal. 5 Our results suggest that the increased waking time observed after the catecholamine agonists is related to an increased availability of NA rather than dopamine.

Effects of pretreatment with 6-hydroxydopamine or noradrenergic receptor blockers on the clonidine-induced distruption of conditioned avoidance responding

The effects of clonidine were assessed on conditioned avoidance responses (CAR) in control, 6-hydroxy-dopamine (6-OHDA)- and vehicle-treated rats, using a shuttle box device. Clonidine (100--400 micrograms/kg) produced a significant decrease of CAR in control and vehicle-treated animals. On the other hand, avoidance responding was only slightly inhibited in the 6-OHDA-lesioned rats. Pretreatment with the alpha-adrenergic blocking drugs yohimbine or phentolamine (1--8 mg/kg) prevented the CAR disrupting effects of clonidine. When animals were pretreated with the beta-adrenergic blocking agent propranolol (1--8 mg/kg) the ensuing injection of clonidine caused a greater CAR depression. Our results further support the hypothesis relating the conditioned performance depression observed after clonidine to the activation of a presynaptic negative feedback mechanism mediated by alpha-adrenoceptors. It is also suggested that propranolol increases the clonidine inhibition through the blockade of a positive feedback mechanism dependent on the activation of presynaptic beta-receptors.

The effects of the combined administration of gamma-hydroxybutyrate and diazepam on sleep parameters in the rat

The actions of diazepam and gamma-hydroxybutyrate (GHB) were assessed on the sleep-wakefulness cycle of male Wistar rats. One and 2 mg/kg diazepam and 12.5 mg/kg GHB had no effects on the sleep variables. After 25 mg/kg GHB, slow wave sleep (SWS2) was significantly increased. Following the combined administration of non-effective doses of GHB and diazepam, significantly higher amounts of SWS2 at the expense of wakefulness were obtained. The injection of a subconvulsant dose of bicuculline (2.5 mg/kg) prior to treatments which significantly increased SWS2 prevented this effect to show up. It is suggested that the actions of GHB and diazepam on the sleep-awake cycle are related to the same neurotransmitter system.

The actions of dopaminergic and noradrenergic antagonists on conditioned avoidance responses in intact and 6-hydroxydopamine-treated rats

The actions of various doses of haloperidol, pimozide, clozapine, and phenoxybenzamine were assessed on a conditioned-avoidance response (CAR) in control and 6-hydroxydopamine-treated rats, using a pole-climbing device. Haloperidol proved to be the most potent in disrupting the CAR. Pimozide was about 1.6 times less potent, and clozapine and phenoxybenzamine were approximately 52 and 155 times less potent than haloperidol, respectively. Prior treatment with 6-hydroxydopamine slightly enhanced the sensitivity to some of the doses of the DA and NE antagonists. Significantly lower levels of responding, however, were observed only after the highest dose of primozide. Clonidine was not only ineffective in reverting avoidance decrements, but also induced a further decline of the CAR. Apomorphine produced a partial, but significant, reversal of the haloperidol and pimozide-induced depression of conditioned responses. Regarding the clozapine-pretreated animals, a significant antagonism was observed only with the smaller dose of apomorphine. The highest dose induced a further decline of the CAR. The DA agonist was also ineffective in the phenoxybenzamine-injected rats. Amphetamine was effective in antagonizing the avoidance decrements produced by all the CA antagonists. Our results support the suggestion that CAR depends on both DA and NE mechanisms. DA seems to be more significant that NE, however, since the CAR was more depressed when receptors depending on the former neurotransmitter were blocked.

Effects of clozapine on the activity of central dopaminergic and noradrenergic neurons

The effects of clozapine on the spontaneous firing rate of noradrenergic (NE, locus coeruleus), dopaminergic (DA, zona compacta, ventral tegmental area) and non-dopaminergic (zona reticulata) neurons was studied in chloral hydrate anesthetized rats. Clozapine administered intraperitoneally significantly increased the spontaneous activity of NE and DA neurons. After a cumulative dose of 8 mg/kg clozapine, the increase of mean firing rate per min of zona compacta and ventral tegmental area neurons attained almost similar values. Amphetamine reversed the clozapine-induced stimulation of NE and DA neurons. Zona reticulata neurons were depressed by clozapine. Neither amphetamine nor physostigmine were effective in antagonizing the inhibition. Our results suggest that clozapine blocks central NE and DA receptors. Furthermore, they fail to reveal a smaller sensitivity of the striatum as compared to the limbic system to the effects of clozapine.

The effects of p-chlorophenylalanine, reserpine, methysergide and cyproheptadine on the dopa-induced EEG synchronization in the rat

The actions of drugs interfering with central indolaminergic mechanisms were assessed on the Dopa-induced EEG synchronization in the rat. The increased slow wave activity observed during the first 30 min following Dopa (100 mg/kg) was significantly decreased by p-chlorophenylalanine (400 mg/kg), reserpine (4 and 8 mg/kg) and methysergide (16 mg/kg). Cyproheptadine was ineffective in this respect. Our findings lend support to the hypothesis that the initial synchronization after Dopa is related to the release of 5-hydroxytryptamine.

Hypnoticlike effects of cannabidiol in the rat

The actions of cannabidiol (CBD), one of the cannabis constituents, were assessed on the sleep-wakefulness cycle of male Wistar rats. During acute experiments, single doses of 20 mg/kg CBD decreased slow-wave sleep (SWS) latency. After 40 mg/kg SWS time was significantly increased while wakefulness was decreased. REM sleep was not significantly modified. Following the once-daily injections of 40 mg/kg CBD for a period of 15 days, tolerance developed to all the above-mentioned effects.

Spontaneous behavior and sleep-wakefulness cycle in isolated and paired REM sleep deprived-marihuana treated rats

The correlation between marihuana-induced aggressive behavior and changes in the sleep-wakefulness cycle was studied in chronically implanted rats. Marihuana injection in non-REM deprived rats did not induce aggressiveness irrespective of the animals being caged in isolation or paired. During this procedure quantization of the sleep-awake cycle revealed that wakefulness was increased while slow wave and REM sleep were decreased, mainly in the paired animals. REM deprived-marihuana injected animals recorded in isolation behaved like the control solution-injected rats. They showed a large rebound of REM and were not aggressive at the end of the 8 hr sessions. Conversely, when these animals were paired during the recording periods, they remained continuously awake and showed numerous episodes of aggressiveness. These results suggest that the aggressiveness inducing properties of marihuana are related to the REM deprivation and to the increased environmental stimulation achieved by pairing the animals.

Increased disrupting effects of haloperidol on a conditioned avoidance response after 6-hydroxydopamine treatment

The influence of prior catecholamine depletion was studied on the behavioral depressant effects of haloperidol using a conditioned avoidance response. The butyrophenone disrupting effects on the avoidance behavior were significantly increased by 6-hydroxydopamine pretreatment.

The actions of flunitrazepam (Rohypnol) on heart and respiratory rates and skin potential fluctuations during the sleep cycle in normal volunteers and neurotic patients with insomnia

The actions of flunitrazepam (Rohypnol) were assessed on the sleep cycle, heart and respiratory rates and skin potential fluctuations of normal volunteers and neurotic patients with insomnia by means of all night recordings. The most conspicuous effect of flunitrazepam (2 mg p.o.) in the healthy subject's sleep cycle was an increase of the latency for the appearance of the first REM period. In the insomniacs the compounds was effective in inducing and maintaining sleep. Flunitrazepam diminished heart rates during the REM phases and significantly decreased the variability indices, this effect being more prominent in the normal subjects. Skin potential fluctuations during stages 2 and REM sleep were also decreased although tolerance developed rapidly in this connection.

The actions of dihydroxyphenylalanine and dihydroxyphenylserine on the sleep-wakefulness cycle of the rat after peripheral decarboxylase inhibition

1. The actions of dihydroxyphenylalanine (DOPA) and dihydroxyphenylserine (DOPS) were assessed on the sleep-wakefulness cycle of male Wistar rats. 2. In comparative studies the extracerebral decarboxylase was inhibited with serinetrihydroxybenzylhydrazide (RO 4-4602) before injection of DOPA or DOPS. 3. DOPA (80-160 mg/kg, i.p.) with or without previous inhibition of the peripheral decarboxylase gave rise to an initial significant increase of slow wave activity, which may be related to a release of 5-hydroxytryptamine. 4. During the subsequent 8 h sessions, DOPA significantly decreased slow wave sleep and rapid eye movement sleep (REM) and increased wakefulness. 5. DOPS (80-160 mg/kg, i.p.) did not significantly modify the sleep-wakefulness cycle apart from a decrease of the latency for the first REM episode after 160 mg/kg in the RO 4-4602 pretreated animals.

Reversal of the 6-hydroxydopamine-induced suppression of a CAR by drugs facilitating central catecholaminergic mechanisms

The intraventricular injection of 6-hydroxydopamine (200 mug) blocked a previously learned conditioned avoidance response (CAR) in rats. The administration of NE, DOPA, amphetamine, phenelzine, desipramine and clonidine induced the reappearance of the CAR. These results are in agreement with current hypotheses on the mechanism of action of 6-hydroxydopamine on the central nervous system.

The incidence of premature contractions in coronary patients during the sleep-awake cycle

Mean heart rates and their variability indices during REM sleep and the frequency of cardiac arrhythmias during the sleep-awake cycle were determined in a group of coronary patients with disturbances of cardiac rhythm. In some patients there was a temporal relationship of atrial and ventricular premature contractions with slow-wave sleep, REM sleep or wakefulness. However, when they were considered as a group, no significant correlation could be observed. Furthermore, the sinus arrhythmia characteristic of REM sleep was not found to be exaggerated in those patients.

Pharmacology of scopinium bromide

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