Effect of p-chlorophenylalanine and tryptophan on sleep, EEG and motor activity in the rat

The effects of zimeldine and alaproclate combined with a small dose of 5-HTP on waking and sleep stages in cats

Sleep and waking stages in cats were studied 8 h following administration of zimeldine and alaproclate, in combination with saline or 5-hydroxy-1-tryptophan (5-HTP). Both drugs in combination with saline reduced rapid eye movement sleep and ponto-geniculo-occipital wave activity, and the effects were potentiated with 5-HTP. After administration of zimeldine in combination with 5-HTP there was an increase in synchronized waking (W-2), followed by an increase in slow wave sleep (SWS), at first SWS-1 with spindles and then highly synchronized SWS-2. The changes were interpreted as reflecting a serotonergic deactivating effect expressed by an electroencephalographic synchronizing effect. This is consistent with earlier studies following serotonin depletion and serotonin precursor loading. After alaproclate in combination with 5-HTP there were changes in W-2 and SWS-1 suggestive of the same process but much less pronounced. The difference between the two serotonin uptake inhibitors is interpreted as being due to regional differences in their uptake inhibition.

Similar effect on REM sleep but differential effect on slow wave sleep of the two 5-HT uptake inhibitors zimeldine and alaproclate in cats and rats

Sleep and waking in cats and rats were studied 6-10 hours following acute administration of zimeldine, alaproclate or saline. The effects on slow wave sleep of the two compounds markedly differed in the cats. Following zimeldine, sleep with a high amount of synchronized slow waves (SWS-2) was increased, and total sleep was unchanged. Following alaproclate, SWS-2 did not increase, and total sleep was reduced. In the rats, zimeldine increased SWS-2 during the first 4 hours after administration, while there was no change in SWS following alaproclate. Both zimeldine and alaproclate increased REM latency and reduced REM sleep in both species with somewhat more pronounced effects in cats than in rats. The results on SWS-2 following zimeldine are consistent with earlier results following serotonin depletion in both species. The differential effects on SWS-2 are discussed in terms of regional differences in uptake inhibition and other differences between the two uptake inhibitors. The results on REM sleep confirm earlier results involving serotonin uptake inhibitors and serotonin precursor loading and indicate that increased synaptic serotonin concentrations suppress REM sleep.

Turnover rate of interstitial albumin in rat skin and skeletal muscle. Effects of limb movements and motor activity

Fractional removal rate (FRR) of radioactive-labelled human serum albumin (I-HSA) injected subcutaneously or intramuscularly was determined by external gamma-detecting equipment. Radioactivity over the injection site fell monoexponentially during registration periods up to 6 h. The FRR was calculated as the turnover rate constant of the radioactivity removal. The FRR fell into one of two ranges: in anaesthetized rats FRR was 0.02-0.03 h-1, and in awake and freely moving rats FRR was 0.08-0.11 h-1. In awake rats, FRR was similar during day and night (spontaneous motor activity is four times higher during the night). Passive limb movements at 1 Hz in anaesthesia increased FRR in skin to that in awake rats, while FRR in skeletal muscle was unchanged. Immobilization resulted in FRR similar to that in anaesthesia. Interstitial albumin mass did not change during 6 h of anaesthesia. It is concluded that the observed FRR reflects steady state changes in albumin turnover. In the awake and freely moving rats at least 3/4 of the removal of albumin is by the lymphatics. Calculated lymph flow was 10 microliters g-1 h-1 and 40 microliters g-1 h-1 in skeletal muscle and skin respectively with corresponding figures during anaesthesia of 3 microliters g-1 h-1 and 10 microliters g-1 h-1 respectively.

Platform sleep deprivation affects deep slow wave sleep in addition to REM sleep

Rats were sleep deprived by the platform method to look for differential effects on light and deep slow wave sleep depending on platform size. Diameters of large and small platforms were 15 cm and 5.1 cm respectively. Sleep was recorded during a baseline light period (09.00-19.00 h), continuously during 48 h of sleep deprivation and during the first lights on recovery period (09.00-19.00 h). In both platform conditions REM sleep was virtually abolished during the first light period (hours 0-10 of sleep deprivation), while NREM sleep was reduced to approximately half of control values. During the second light period (hours 22-34 of sleep deprivation) REM sleep recovered somewhat in the large platform group. Light slow wave sleep (SWS-1) was comparable to baseline while deep slow wave sleep (SWS-2) was still significantly reduced. In the small platform group both SWS-2 and REM sleep was considerably reduced on day 2. Over the whole deprivation period there was an effect of platform size on SWS-1 (higher in the small platform group), and on SWS-2 and REM sleep (lower in the small platform group). During the 9 h light-time recovery sleep there was an REM sleep rebound in both groups. SWS-1 was reduced in both groups while SWS-2 was not significantly increased. The ratio SWS-2/SWS-1 was, however, significantly increased only in the small platform group recovery sleep. The results suggest that platform sleep deprivation deprives the animals of deep slow wave sleep in addition to REM sleep. This has implications for conclusions on REM sleep function based upon REM sleep deprivation.

Partial insomnia, hyperactivity and hyperdipsia induced by repeated administration of toluene in rats: their relation to brain monoamine metabolism

In an attempt to examine chronic effects of toluene on sleep, spontaneous locomotor activity and drinking behavior, rats were repeatedly administered toluene i.p. at doses of 100 and 200 mg/kg body weight for 14 consecutive days. The 200-mg/kg injections induced a decrease in total sleep on Day 1, an increase in locomotor activity on Days 1 through 4 and an increase in drinking activity on Days 0 through 6 after discontinuation of the daily injections. Both the reduced sleep and the increased locomotor activity appeared during the light period, whereas the drinking activity increased during the dark period. In order to find neurochemical correlates of the toluene-induced changes in behavior, regional concentrations of brain monoamines and their metabolites were determined. The toluene-induced partial insomnia and hyperactivity were associated with lowered concentrations of serotonin in frontal cortex, hippocampus and midbrain and 5-hydroxyindoleacetic acid in midbrain and hypothalamus. The increased drinking activity was associated with increased concentrations of striatal 3,4-dihydroxy-phenylacetic acid and homovanillic acid and hypothalamic noradrenaline and 3-methoxy-4-hydroxyphenylethyleneglycol. Central monoaminergic mechanisms were implicated in the toluene-induced partial insomnia, hyperactivity and hyperdipsia.

Effect of local 5,6-dihydroxytryptamine on the rat olfactory bulb responsiveness during wakefulness and sleep

This study investigated a possible participation of the centrifugal serotonergic (5-HT) innervation of the olfactory bulb (OB) in the control of the multiunit mitral cell responsiveness in behaving rats. A bilateral injection of 5,6-dihydroxytryptamine solution (5,6-DHT) into the OB induced in this structure an average 70% reduction in the level of endogenous serotonin. Control and treated animals were habituated to eat a single 2 h daily meal. Recording sessions were performed either after a 22 h fasting period or just after the meal. The summated multiunit mitral cell activity and vigilance state parameters were recorded in the absence of and during repeated stimulation by puffs of food odour and isoamyl acetate. The results showed that the 5,6-DHT treatment did not modify significantly previously established centrifugal controls exerted at the OB level: (1) the selective enhancement of the mitral cell responsiveness to food odour occurring in waking food-deprived animals; (2) the inhibition of the olfactory input during slow wave sleep. However, the considered 5-HT projections could mediate some inhibitory influence on mitral cell activity during wakefulness only. Finally, the 5-HT innervation of the OB did not seem to be involved in basic mechanisms of olfactory recognition.

Effects of metergoline and quipazine on locomotor activity of rats in novel and familiar environments

Many studies have investigated the effects on locomotor activity of various manipulations of the brain's serotonin (5-hydroxytryptamine, 5-HT) systems but the results have not been consistent. However, besides employing different techniques for manipulating brain 5-HT, previous studies have differed in size of apparatus, amount of apparatus pre-exposure and length of session. To test the possibility that apparatus familiarity interacts with the effects of 5-HT manipulations on locomotor activity, this variable was manipulated in groups of rats treated with the 5-HT receptor blocker, metergoline or the agonist, quipazine. Within each drug treatment group, 18 rats had prior experience with the activity monitoring photocell chambers (pre-exposed condition) and 18 were not previously exposed (novel condition); each condition was further subdivided into 3 dose subgroups (n = 6). Testing consisted of 3 30-min sessions with subgroups receiving metergoline (0, 2.5, 5.0 mg/kg) or quipazine (0, 2.5, 5.0 mg/kg) 30 min before. Results with metergoline treatment revealed no significant drug effect in the pre-exposed groups but a decrease in activity in the novel condition. Quipazine, on the other hand, had no significant effect in the novel condition but produced a time-dependent effect on activity in the pre-exposed condition. These results suggest that the effects on locomotor activity of compounds affecting 5-HT neurotransmission may interact with the familiarity of the test apparatus and with the duration of testing. Interexperiment differences in these variables may account for some of the inconsistencies previously reported.

Effect of S-adenosyl-L-homocysteine upon sleep in p-chlorophenylalanine pretreated rats

S-Adenosyl-L-homocysteine (7 mg/kg), administered to PCPA-pretreated rats, was able to restore normal SWS and PS quantities, as well as circadian rhythms. This effect was at its maximum when SAH was injected 48 h after PCPA (400 mg/kg). These results are discussed in terms of post-synaptic synergetic control by SAH of serotonergic and noradrenergic nerve terminals via the periventricular system and caudal medulla in relation to environmental input.

The effect of sleep deprivation on sleep in rats with suprachiasmatic lesions

The effect of 24-h sleep deprivation on sleep was investigated in rats whose circadian rest-activity rhythms were extensively disrupted by bilateral lesions of the suprachiasmatic nuclei (SCN). Sleep deprivation caused an increase in total sleep, REM sleep and the slow wave sleep fraction of non-REM sleep. It is concluded that the homeostatic component of sleep regulation is morphologically and functionally distinct from the circadian component.

Significance of biogenic amines for opioid-induced locomotor activity in rats

The effect of the opioid levorphanol on locomotor activity was investigated in rats treated with p-chlorophenylalanine (PCPA) or 6-hydroxydopamine (6-OHDA). Acute oral administration of 10 or 30 mg/kg levorphanol induces a time- and dose-dependent alteration in motility. Ingestion of 10 mg/kg levorphanol in rats with an intact biogenic amine content results in an increase of locomotion for 180 min followed by a longer lasting, small but significant, reduction of motor activity. The course of motility after 30 mg/kg is similar to that after 10 mg/kg, but the initial peak appears after a 3-h delay. In 5-hydroxytryptamine (5-HT)-deficient rats, the first excitation of motility is enhanced and its subsequent depression intensified. After administration 30 mg/kg a general reduction in motor activity occurs. The effect of 10 mg/kg levorphanol after 6-OHDA treatment is on a lower level, similar to that of rats with intact amine content. After 30 mg/kg levorphanol an immediate and longer lasting increase in activity appears. Chronic ingestion of about 40 mg/levorphanol/kg per day enhances the total amount of activity in normal rats as well as in animals with catecholamine (CA) depletion, but not in those treated with PCPA. In all cases, withdrawal of the opioid results in a reduction of activity below that of control levels.

Increased sleep following intracerebroventricular injection of the delta sleep-inducing peptide in rats

Synthetic delta sleep-inducing peptide (DSIP) was injected intracerebroventricularly into rats in a dose of 7 nmol/kg. A significant, 20% increase in total slow wave sleep (and total sleep) was found in the DSIP-injected rats, compared to a baseline recording following a sham injection procedure. Rats injected with the Ringer solution vehicle did not change their sleep compared to their baseline recording.

Serotoninergic mechanisms and sleep rebound

The administration of p-chlorophenylalanine (PCPA), an inhibitor of serotonin (5-HT) biosynthesis, at the end of a 48 h sleep deprivation does not impair the subsequent rebound of deep slow wave sleep (SWS2) and paradoxical sleep (PS). On the contrary, the administration of PCPA during a 48 h sleep deprivation is followed by a great decrease of light slow wave sleep (SWS1) and by total disappearance of SWS2 while some rebound of PS still occurs in narcoleptic-like attacks. These experiments provide evidence that sleep inducing materials are accumulated during sleep deprivation. Serotoninergic processes appear to be involved in the regulatory mechanisms of the biosynthesis and the accumulation of SWS2 and PS factors.

Effect of ambient temperature on the 24-hour sleep-wake cycle in normal and capsaicin-treated rats

The 24-hour sleep-wake cycle of untreated, normal rats and of capsaicin-treated rats was continuously recorded by telemetry. Recordings were made on two baseline days at 22 degrees C, two days at 29 degrees C, and two final days at 22 degrees C. In untreated animals the daily amount of waking was reduced by the elevated ambient temperature and nonREM sleep was enhanced. This effect was mainly due to the frequent interruption of the dark-time waking episodes by sleep. In capsaicin-treated animals, raising the ambient temperature did not significantly enhance sleep. However, in both groups of rats the slow wave sleep (SWS) fraction of nonREM sleep was increased after elevating the temperature to 29 degrees C. REM sleep showed a minor increase which was significant only for the capsaicin-treated group. The results suggest that a moderate increase of ambient temperature has two effects: (1) It causes an enhancement of sleep by a reduction in the duration of waking episodes, an effect that may represent a heat-defense response. The attenuation of this response in capsaicin-treated rats may be a consequence of the impairment of warm-receptors. (2) It favors the occurrence of SWS and REM sleep.

Effect of voluntary locomotor activity on sleep in the rat

The effect of voluntary wheel-turning activity on sleep was investigated in the rat. In addition to scoring the conventional sleep states, a frequency analysis of the telemetrically recorded EEG-signal was performed to define a slow wave sleep (SWS) fraction of non-REM sleep (NREMS). The animals had access to the running-wheel during the first 3.5 days and the last 2.5 days of the 8-day recording period, but were prevented from entering the wheel in the 2 intervening days. Wheel-running (average distance run per day: 3015 m) occurred mainly during the dark-phase. The level of SWS was not significantly different for periods with access and without access to the wheel. The dark-time level of SWS relative to NREMS showed a trend towards higher values in the wheel-access period. The dark-time level of REM sleep was negatively correlated with the distance run in the wheel, and was lower in the access nights than in the no-access nights. Although locomotor activity produced some shifts in the sleep state distribution in the dark-phase, it had practically no effect on the rat's main daily sleep period in the light-phase.