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The medical uses of cannabidiol (CBD), a constituent of the Cannabis sativa, have accelerated the legal and social acceptance for CBD-based medications but has also given the momentum for questioning whether the long-term use of CBD during the early years of life may induce adverse neurobiological effects in adulthood, including sleep disturbances. Given the critical window for neuroplasticity and neuro-functional changes that occur during stages of adolescence, we hypothesized that CBD might influence the sleep-wake cycle in adult rats after their exposure to CBD during the adolescence. Here, we investigated the effects upon behavior and neural activity in adulthood after long-term administrations of CBD in juvenile rats. We pre-treated juvenile rats with CBD (5 or 30 mg/Kg, daily) from post-natal day (PND) 30 and during 2 weeks. Following the treatments, the sleep-wake cycle and NeuN expression was analyzed at PND 80. We found that systemic injections of CBD (5 or 30 mg/Kg, i.p.) given to adolescent rats (post-natal day 30) for 14 days increased in adulthood the wakefulness and decreased rapid eye movement sleep during the lights-on period whereas across the lights-off period, wakefulness was diminished and slow wave sleep was enhanced. In addition, we found that adult animals that received CBD during the adolescence displayed disruptions in sleep rebound period after total sleep deprivation. Finally, we determined how the chronic administrations of CBD during the adolescence affected in the adulthood the NeuN expression in the suprachiasmatic nucleus, a sleep-related brain region. Our findings are relevant for interpreting results of adult rats that were chronically exposed to CBD during the adolescence and provide new insights into how CBD may impact the sleep-wake cycle and neuronal activity during developmental stages.

Cannabidiolic acid methyl ester (HU-580) is a more stable compound than cannabidiolic acid (CBDA) which has been shown to be effective in reducing nausea, anxiety, depression behaviors in animal models. Here we extend the investigation of this compound to determine its effect on the sleep-wake cycle in male Wistar rats. HU-580 dose-dependently (0.1, 1.0 or 100 μg/Kg, i.p.) prolonged wakefulness (W) and decreased slow wave sleep (SWS) duration whereas rapid eye movement sleep (REMS) showed no statistical change. In addition, the brain microdialysis probes either placed at nucleus accumbens (NAc) or into the basal forebrain in freely moving animals were used to evaluate the effects of HU-580 treatment on neurotransmitters related to the sleep-wake cycle modulation. HU-580 enhanced extracellular levels of dopamine, serotonin collected from NAc while adenosine and acetylcholine were increased in basal forebrain. In summary, HU-580 seems to possess wake-promoting pharmacological properties and enhances the levels of wake-related neurochemicals. This is the first report of effects of HU-580 on sleep modulation expanding the very limited existent data on the neurobiological effects of HU-580 on rats.

© Springer-Verlag GmbH Germany, part of Springer Nature 2020., Rationale: The nuclear receptor retinoid X receptor (RXR) belongs to a nuclear receptor superfamily that modulates diverse functions via homodimerization with itself or several other nuclear receptors, including PPARα. While the activation of PPARα by natural or synthetic agonists regulates the sleep-wake cycle, the role of RXR in the sleep modulation is unknown. Objectives: We investigated the effects of bexarotene (Bexa, a RXR agonist) or UVI 3003 (UVI, a RXR antagonist) on sleep, sleep homeostasis, levels of neurochemical related to sleep modulation, and c-Fos and NeuN expression. Methods: The sleep-wake cycle and sleep homeostasis were analyzed after application of Bexa or UVI. Moreover, we also evaluated whether Bexa or UVI could induce effects on dopamine, serotonin, norepinephrine epinephrine, adenosine, and acetylcholine contents, collected from either the nucleus accumbens or basal forebrain. In addition, c-Fos and NeuN expression in the hypothalamus was determined after Bexa or UVI treatments. Results: Systemic application of Bexa (1 mM, i.p.) attenuated slow-wave sleep and rapid eye movement sleep. In addition, Bexa increased the levels of dopamine, serotonin, norepinephrine epinephrine, adenosine, and acetylcholine sampled from either the nucleus accumbens or basal forebrain. Moreover, Bexa blocked the sleep rebound period after total sleep deprivation, increased in the hypothalamus the expression of c-Fos, and decreased NeuN activity. Remarkably, UVI 3003 (1 mM, i.p.) induced opposite effects in sleep, sleep homeostasis, neurochemicals levels, and c-Fos and NeuN activity. Conclusions: The administration of RXR agonist or antagonist significantly impaired the sleep-wake cycle and exerted effects on the levels of neurochemicals related to sleep modulation. Moreover, Bexa or UVI administration significantly affected c-Fos and NeuN expression in the hypothalamus. Our findings highlight the neurobiological role of RXR on sleep modulation., This work was supported by the Escuela de Medicina, Universidad Anáhuac Mayab (PresInvEMR2018), given to E. MR.

Cannabis and, to a lesser extent, synthetic cannabinoids are used during adolescence, a period in which multiple brain areas are still undergoing development. Among such areas is the hypothalamus, which is implicated in the control of sleep-wake cycle. In the present report, we show that exposing adolescent rats to the cannabinoid receptor agonist WIN 55, 212–2 (0.1, 0.3 or 1.0 mg/kg, i.p) for 14 days during adolescence (i.e., from post-natal day 30–44) resulted in significant sleep disturbances when the animals became adult (post-natal day 80). These included decreased wakefulness and enhanced rapid eye movement sleep. Furthermore, we found that labeling for NeuN, a marker of postmitotic neurons, was significantly increased the dorsomedial hypothalamic nucleus of rats treated with WIN 55, 212–2. The results suggest that excessive cannabinoid receptor activation during adolescence can persistently influence sleep patterns and neuronal activity later in life.

The peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear protein that plays an essential role in diverse neurobiological processes. However, the role of PPARα on the sleep modulation is unknown. Here, rats treated with an intrahypothalamic injection of Wy14643 (10μg/1μL; PPARα agonist) enhanced wakefulness and decreased slow wave sleep and rapid eye movement sleep whereas MK-886 (10μg/1μL; PPARα antagonist) promoted opposite effects. Moreover, Wy14643 increased dopamine, norepinephrine, serotonin, and adenosine contents collected from nucleus accumbens. The levels of these neurochemicals were diminished after MK-886 treatment. The current findings suggest that PPARα may participate in the sleep and neurochemical modulation.

Continuous spontaneous alternation behavior (SAB) in a Y-maze is used for evaluating working memory in rodents. Here, the design of an automated Y-maze equipped with three infrared optocouplers per arm, and commanded by a reduced instruction set computer (RISC) microcontroller is described. The software was devised for recording only true entries and exits to the arms. Experimental settings are programmed via a keyboard with three buttons and a display. The sequence of arm entries and the time spent in each arm and the neutral zone (NZ) are saved as a text file in a non-volatile memory for later transfer to a USB flash memory. Data files are analyzed with a program developed under LabVIEW® environment, and the results are exported to an Excel® spreadsheet file. Variables measured are: latency to exit the starting arm, sequence and number of arm entries, number of alternations, alternation percentage, and cumulative times spent in each arm and NZ. The automated Y-maze accurately detected the SAB decrease produced in rats by the muscarinic antagonist trihexyphenidyl, and its reversal by caffeine, having 100 % concordance with the alternation percentages calculated by two trained observers who independently watched videos of the same experiments. Although the values of time spent in the arms and NZ measured by the automated system had small discrepancies with those calculated by the observers, Bland-Altman analysis showed 95 % concordance in three pairs of comparisons, while in one it was 90 %, indicating that this system is a reliable and inexpensive alternative for the study of continuous SAB in rodents.

Modafinil (MOD) it has to be considered as a wake-inducing drug to treat sleep disorders such as excessive sleepiness in narcolepsy, shift-work disorder, and obstructive/sleep apnea syndrome. Current evidence suggests that MOD induces waking involving the dopamine D1 receptor. However, little is known regarding the molecular elements linked in the wake-promoting actions of MOD. Since the D1 receptor activates the mitogen-activated protein kinase (MAP-K) cascade, it raises the interesting possibility that effects of MOD would depend upon the activation of MAP-K. Here we tested the expression of MAP-K in hypothalamus as well as pons after the microinjection of MOD (10 or 20 μg/1 μL) in rats into anterior hypothalamus, a wake-inducing brain area. Intrahypothalamic injections of MOD promoted MAP-K phosphorylation in hypothalamus and pons. Taken together, these results suggest that the wake-inducing compound MOD promotes the MAP-K phosphorylation.

Cannabis sativa is a plant that contains more than 500 components, of which the most studied are Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD). Several studies have indicated that CBD displays neurobiological effects, including wake promotion. Moreover, experimental evidence has shown that injections of CBD enhance wake-related compounds, such as monoamines (dopamine, serotonin, epinephrine, and norepinephrine). However, no clear evidence is available regarding the effects of CBD on additional wake-related neurochemicals such as acetylcholine (ACh). Here, we demonstrate that systemic injections of CBD (0, 5, 10 or 30 mg/kg, i.p.) at the beginning of the lights-on period, increase the extracellular levels of ACh collected from the basal forebrain and measured by microdialysis and HPLC means. Moreover, the time course effects on the contents of ACh were present 5 h post-injection of CBD. Altogether, these data demonstrate that CBD increases ACh levels in a brain region related to wake control. This study is the first to show the effects of ACh levels in CBD-treated rats and suggests that the basal forebrain might be a site of action of CBD for wakefulness modulation.

The peroxisome proliferator-activated receptor alpha (PPARα) is a member of the nuclear receptor superfamily that has been suggested as a modulator of several physiological functions. The PPARα recognizes as an endogenous ligand the anorexic lipid mediator oleoylethanolamide (OEA) which displays wake-inducing properties. Despite that recent evidence indicates that activation of PPARα by synthetic agonists such as Wy14643 enhances waking as well as the extracellular contents of wake-related neurotransmitters, the role of PPARα in sleep recovery after prolonged waking has not been fully described. Thus, the aim of this study was to characterize if PPARα regulates sleep rebound after total sleep deprivation (TSD). We report that after 6 h of TSD activation of PPARα by pharmacological systemic administration of OEA (10, 20 or 30 mg/Kg, i.p.) promoted alertness by blocking the sleep rebound after TSD. Besides, wake-linked compounds such as dopamine, norepinephrine, serotonin, or adenosine collected from nucleus accumbens were enhanced after TSD in OEA-treated animals. These sleep and neurochemical results were mimicked after injection of PPARα agonist Wy14643 (10, 20, 30 mg/Kg, i.p.). However, similar findings from the sham of vehicle groups were observed if PPARα antagonist MK-886 was administered to rats (10, 20, 30 mg/Kg, i.p.). Our results strengthened the hypothesis that PPARα might modulate sleep and neurochemical homeostasis after sleep deprivation.

Anatomical and functional studies have shown that the NADPH-diaphorase-positive cholinergic neurons of the pedunculopontine nucleus (PPN) send projections to several areas in the brain. The purpose of this work was to investigate whether bilateral lesions with quinolinic acid, a neurotoxin with greater selectivity for NADPH-diaphorase-positive neurons, aimed at the compact portion of the PPN would affect the performance of adaptive behaviors, such as sleep, locomotion, and spontaneous alternation. Lesioned animals were divided in a low lesion group (LL

Extrapyramidal syndromes (EPS) impose a heavy burden on patients receiving antipsychotic therapy. Anticholinergics are the drugs of choice for preventing EPS, but they also produce many adverse reactions. Using the EPS model of haloperidol-induced catalepsy we evaluated the potential therapeutic value of a mixture of low doses of the non-selective adenosine antagonist theophylline (0.93 and 1.86 mg/kg), and the muscarinic antagonists benztropine (0.134 and 0.268 mg/kg) and ethopropazine (0.116 and 0.232 mg/kg). In rats pretreated with vehicle (distilled water), the cumulative catalepsy time over 5 h was 4199 ± 228 s, and the mean latency was 67.5 ± 7.8 min. Applied separately, neither of the drugs at the doses used caused significant changes of catalepsy intensity vs. control rats. However, the combination of the larger doses of theophylline and benztropine caused a significant reduction of catalepsy intensity (− 41 ± 10%) compared with the effects of the vehicle, vs. the lower dose of benztropine, and vs. both doses of theophylline alone. The mixture of the larger doses of theophylline and benztropine also delayed catalepsy onset (156 ± 21 min) as compared with the lower doses of these same drugs applied alone. In the case of theophylline plus ethopropazine, only the association of the larger doses showed a non-significant tendency to inhibit catalepsy (− 21 ± 8%) and to prolong its latency (108 ± 13 min). Further, neither catalepsy intensity nor its latency was affected by a combination of the selective A 1 R antagonist DPCPX (1 mg/kg,) with the larger doses of both anticholinergics. In contrast, the anticholinergics showed synergism with a subthreshold dose of the selective A 2A R antagonist ZM 241395 (0.5 mg/kg), causing a significant reduction of catalepsy intensity (ethopropazine, − 27 ± 5%; benztropine, − 35 ± 9%) and prolonging its latency (ethopropazine, 65 ± 9 min; benztropine, 78 ± 11 min), compared with the effect of their respective vehicle (DMSO plus mineral oil: catalepsy time, 5100 ± 196 s; latency, 17.5 ± 2.5 min). These findings suggest that neuroleptic-induced EPS could be effectively controlled by a combination of lower doses of theophylline and anticholinergics, with the advantage of maximizing their efficacy and minimizing their adverse reactions.

Increasing evidence suggests that sleep alterations could favor subsequent depression development. In order to identify the simultaneous occurrence of these parameters in young people, in this work we evaluated the prevalence of depressive symptoms, sleep habits, and possible sleep disturbances in college students.Beck Depression Inventory (BDI), Epworth Sleepiness Scale (ESS), and a Sleep Habits Questionnaire were applied to students registered at the Autonomous University of Yucatan, Merida (mean age 20.2 +/- 2.6 years). The final sample was composed of 340 (53%) women and 298 (47%) men. Reliability of the BDI and ESS was assessed by Cronbach's alpha method.Taking 10 as ESS cut-off point, it was found that 31.6% of the students had a high level of sleepiness. Students with depressive symptoms had a greater number of days with somnolence during class (p0.05) and perceived that this affected their academic performance at a higher level (p0.001) than the students without symptoms. In comparison to subjects without depressive symptoms, students with those symptoms rated their sleep quality as poor (p0.001), perceived a greater latency to initiate sleep after going to bed (p0.03), and experienced a greater number of awakenings (p0.04).We found diverse sleep alterations in a large proportion of the studied subjects, which were more severe in those who showed depressive symptoms. Educating students for appropriate sleep hygiene and encouraging them to seek professional advice to treat sleep disturbances may be useful to prevent depression.

Administration of d-glucose enhances learning and memory in several tasks and also attenuates memory impairments and other behavioral effects of several drugs, including morphine. The present experiment compared the effects of peripherally administered d-glucose with those of l-glucose, a stereoisomer of d-glucose that is not metabolized and does not readily cross the blood-brain barrier. Like d-glucose, though at somewhat different doses, peripherally administered l-glucose attenuated morphine-induced deficits in spontaneous alternation performance in rats and mice and attenuated morphine-induced hyperactivity in mice. l-Glucose did not raise circulating levels of plasma d-glucose, suggesting that the effects of l-glucose are not secondary to increased availability of d-glucose. Using direct injections of d- and l-glucose and morphine into the medial septum of rats, the findings indicate that d-glucose but not l-glucose attenuated morphine-induced deficits in spontaneous alternation performance; indeed, intraseptal injections of l-glucose alone impaired spontaneous alternation performance. These findings suggest that peripheral l-glucose antagonizes morphine-induced behavioral effects by a peripheral signaling mechanism, one distinct from the mechanisms that mediate at least some of the effects of d-glucose on brain function.

Cannabidiol (CBD) is a constituent of Cannabis sativa that promotes wakefulness as well as enhances endogenous levels of wake-related neurotransmitters, including dopamine. However, at this date, the effects of CBD on the sleep-inducing molecules, such as adenosine (AD), are unknown. Here, we report that intrahypothalamic injection of CBD (10μg/1μL) increases the extracellular levels of AD collected from nucleus accumbens. Furthermore, the pharmacodynamic of this drug shows that effects on the contents of AD last 2h post-injection. These preliminary findings suggest that CBD promotes the endogenous accumulation of AD.

Glucose administration reverses the effects of both muscarinic and nicotinic cholinergic receptor antagonists on memory and other measures. In experiment 1, we found that glucose attenuated impairments on spontaneous alternation after muscarinic (scopolamine, 0.5 mg/kg) or nicotonic (mecamylamine, 5.0 mg/kg) receptor blockade. In experiment 2, we examined whether glucose could reverse the spontaneous alternation impairments produced by combined muscarinic-nicotinic receptor blockade. Scopolamine (0.1 mg/kg) and mecamylamine (2.5 mg/kg) when administered separately did not modify alternation performance, but when coadministered they decreased spontaneous alternation scores. This decrease was attenuated by glucose at 100, 300, 500 and 3000 mg/kg. These findings suggest that glucose may attenuate the behavioral impairment by enhancing cholinergic activity and/or other neurotransmitter systems.

Chronic caffeine consumption has been inversely associated with the risk of developing dementia and Alzheimer's disease. Here we assessed whether chronic caffeine treatment prevents the behavioral and cognitive decline that male Wistar rats experience from young (≈3 months) to middle age (≈10 months). When animals were young they were evaluated at weekly intervals in three tests: motor activity habituation in the open field (30-min sessions at the same time on consecutive days), continuous spontaneous alternation in the Y-maze (8 min), and elevated plus-maze (5 min). Afterward, rats from the same litter were randomly assigned either to a caffeine-treated group (n=13) or a control group (n=11), which received only tap water. Caffeine treatment (5 mg/kg/day) began when animals were ≈4 months old, and lasted for 6 months. Behavioral tests were repeated from day 14 to day 28 after caffeine withdrawal, a time period that is far in excess for the full excretion of a caffeine dose in this species. Thirty days after caffeine discontinuation brains were processed for Golgi-Cox staining. Compared with controls, we found that middle-aged rats that had chronically consumed low doses of caffeine (1) maintained their locomotor habituation during the second consecutive day exposure to the open field (an index of non-associative learning), (2) maintained their exploratory drive to complete the conventional minimum of nine arm visits required to calculate the alternation performance in the Y-maze in a greater proportion, (3) maintained their alternation percentage above chance level (an index of working memory), and (4) did not increase the anxiety indexes assessed by measuring the time spent in the open arms of the elevated plus maze. In addition, morphometric analysis of hippocampal neurons revealed that dendritic branching (90–140 μm from the soma), length of 4th and 5th order branches, total dendritic length, and spine density in distal dendritic branches were greater in the basal but not the apical dendrites of CA1 pyramidal neurons from rats chronically treated with caffeine, in comparison with their age- and littermate-matched controls. Altogether, the present findings strengthen the epidemiological observations suggesting that prolonged caffeine intake prevents the cognitive decline associated with aging, and open the possibility that this process could be mediated by promoting the growth of dendrites and spines in neurons of the adult mammalian brain.

The methylenetetrahydrofolate reductase (MTHFR) C677T mutation has been associated to high homocysteine levels and schizophrenia. Since cytokines are altered in schizophrenia and increments of homocysteine could promote an inflammatory response, it was investigated whether interleukin-6 (IL-6) and tumor necrosis factor alfa (TNFalpha) levels are modulated by the MTHFR genotype. Serum levels of TNFalpha, IL-6, B(12), homocysteine, folate and red blood cell (RBC) folate as well as the MTHFR genotype were determined in a group of schizophrenic patients and compared to those of a control group. RBC folate levels were reduced and homocysteine and the two cytokines' concentrations were elevated in all patients as compared to controls. RBC folate in both heterozygous (CT) and homozygous (TT) patients was significantly different to that of their respective control groups. Homocysteine levels found in patients were significantly higher than those found in controls, only in individuals carrying the TT genotype. Cytokine levels were augmented in the group of patients irrespective of the genotype, and significant differences were found in all cases, except for TNFalpha levels in those subjects carrying the CC genotype. After adjusting for sex, low levels of RBC folate, high levels of homocysteine, both medium and high levels of TNFalpha and high IL-6 levels were associated with schizophrenia. MTHFR genotype was not a risk factor for developing the disease, although a larger sample is required to confirm this finding.

Trihexyphenidyl (THP) is a drug commonly used to reduce parkinsonian symptoms. An important side effect of this agent is memory impairment. Since caffeine enhances the potency of THP to inhibit haloperidol-induced catalepsy, caffeine may be used as an adjuvant of lower doses of THP, in order to improve its antiparkinsonian effects without causing memory disruption. To further assess the synergism between caffeine and THP, both drugs were tested in reserpinized rats, another preclinical model of Parkinson's disease. Four groups of rats (n = 7) were treated with reserpine (5 mg/kg, i.p.). A control group (n = 7) was treated only with the vehicle for reserpine (dimethylsulphoxide). The spontaneous locomotor behavior was tested 24 h later in a box with infrared sensors, 30 min after receiving one of the following treatments: distilled water (1 ml/kg), caffeine (1 mg/kg), THP (0.1 mg/kg) or caffeine plus THP. The levels of horizontal locomotion (14 +/- 5%) and vertical exploration (15 +/- 10%) were significantly lower in reserpinized rats treated with distilled water, compared with the mean activity values (100%) recorded in animals pretreated only with the vehicle for reserpine. The reserpine-induced hypokinesia was neither reversed by caffeine alone nor by THP alone. However, the combination of caffeine plus THP restored locomotion (141 +/- 19%) and vertical exploration (82 +/- 17%) to levels not significantly different to those of non-reserpinized rats. Moreover, the time-course of locomotion and exploration displayed the characteristic habituation over time, in which short-term memory processes are involved. Also, the thigmotaxis index indicated that the combined treatment did not induce anxiety-like behavior. Hence, these results support the proposal that low, subthreshold doses of caffeine plus THP have the potential to alleviate the motor disabilities in parkinsonian patients, with a low risk of causing anxiety or memory impairment.

The possible synergism between caffeine and muscarinic antagonists to inhibit haloperidol-induced catalepsy was investigated with the bar test in rats. Pretreatment with low doses of caffeine (1-3 mg/kg), a non-selective adenosine antagonist, dose dependently reduced the intensity and increased the onset latency of catalepsy induced by haloperidol (0.5-2 mg/kg). Similar effects were produced by the muscarinic antagonists atropine (4.1 mg/kg), and trihexyphenidyl (THP, 0.01-3 mg/kg). THP inhibited catalepsy intensity with an ED(50) of 0.38 mg/kg, and increased its onset latency with an ED(50) of 0.52 mg/kg. The anticataleptic effect of anticholinergics was potentiated when a low dose of caffeine (1 mg/kg) was applied simultaneously. In the presence of caffeine, THP inhibited catalepsy intensity with an ED(50) of 0.19 mg/kg, and prolonged the latency with an ED(50) of 0.30 mg/kg. The synergism was more evident when THP was administered at subthreshold doses that were unable to modify haloperidol-induced catalepsy when applied alone, but produced a clear inhibition of catalepsy when injected with caffeine. To assess whether repeated administration of caffeine could induce tolerance to the synergism with THP, a group of rats was pretreated with three daily doses of caffeine (1 mg/kg) for seven days, and the catalepsy test was performed on the eighth day. In these animals, caffeine was still able to enhance the anticataleptic actions of THP, suggesting that repeated administration of 1 mg/kg caffeine does not induce tolerance to the synergism with anticholinergics. These results indicate that low doses of caffeine enhance the anticataleptic actions of muscarinic antagonists, and leave open the possibility of using caffeine as adjunctive therapy to reduce the doses and the adverse effects of anticholinergics in Parkinson's disease.

The nigrostriatal dopaminergic neurons of the substantia nigra pars compacta (SNc) and the nondopaminergic neurons of the substantia nigra pars reticulata (SNr) receive a dense synaptic input from the serotonergic neurons of the raphe nuclei. To assess whether serotonin [5-hydroxytryptamine (5-HT)] spontaneously released at the substantia nigra could modulate motor activity, the 5-HT reuptake inhibitors (SRIs), duloxetine (6–12 nmol) and clomipramine (12 nmol), were unilaterally microinjected either into the SNc or the SNr of freely moving rats, and the circling behavior was counted with an automated rotometer. In the SNc, the main effect of the SRIs was a contraversive circling behavior that was not observed when applied at distances ≥0.2 mm above the SNc. The circling induced by clomipramine was blocked by microinjection of haloperidol (53 nmol) into the ipsilateral neostriatum, suggesting that the circling elicited by microinjection of the SRIs into the SNc depends on an intact striatal dopaminergic transmission. Microinjection of 5-HT (21 nmol) only produced a significant contraversive circling response when it was coinjected with the SRIs. Pretreatment with methysergide (1 mg/kg ip), a nonselective 5-HT 2 antagonist, did not block the circling elicited by microinjection of clomipramine into the SNc, either alone or in combination with 5-HT. However, microinjection of the 5-HT 2 antagonist mianserin (2 nmol) into the SNc partially inhibited the circling induced by duloxetine (6 nmol), alone or coinjected with 5-HT. Since current theories of circling behavior hypothesize that the animal turns away from the cerebral hemisphere where dopamine neurotransmission predominates, these results suggest that the contraversive circling induced by the unilateral microinjection of SRIs into the SNc could be mediated by a 5-HT-induced increase of firing frequency of nigrostriatal dopaminergic neurons. When applied into the SNr, clomipramine and duloxetine also elicited a contraversive circling behavior and enhanced the circling induced by 5-HT. Systemic methysergide (1 mg/kg ip), but not intranigral mianserin (2 nmol), blocked the circling elicited by microinjection of clomipramine into the SNr, either alone or in combination with 5-HT. These results suggest that 5-HT 2 -like receptors are involved in the contraversive circling induced by enhancement of serotonergic transmission in the SNr.

We investigated whether the infection with Trypanosoma cruzi in rats could produce functional alterations of the central nervous system. The experimental group received an injection of 150,000 trypomastigotes / rat, whereas the control group received a saline injection. Spontaneous alternation behavior (SAB) tests and sleep-wake cycle recordings were obtained at the end of the parasitaemia. Results showed that the infected animals had significant sleep impairments, as denoted by an increase in the number of wake periods and a reduction of rapid eye movement sleep amount. SAB performance was also found to be impaired in these animals, as compared to the control group. Our results suggest that the rat is a suitable model for brain dysfunction studies in Chagas' disease.

Morphine effects on many neural and behavioral measures, including tests of learning and memory, are attenuated by increased circulating glucose levels. Using systemic injections, we investigated the ability of glucose to attenuate sleep deficits induced by morphine administration in the rat. Morphine at 1 mg/kg produced a moderate decrease in slow wave sleep which was prevented by concomitant administration of 100 mg/kg of glucose. A higher dose of morphine (10 mg/kg) severely delayed the onset of both slow wave sleep and REM sleep. These delays were attenuated by concurrent administration of 250 mg/kg of glucose. Thus, glucose reversals of morphine effects are also extended to measures of sleep.

Auditory stimulation applied during rapid eye movement (REM) sleep enhances the duration of REM sleep in cats and humans. The present experiment investigated whether auditory stimulation would enhance REM sleep in young (3-6 months) rats, and also in old (22-24 months) rats which have impaired REM sleep. Baseline sleep records were obtained on two days. Sleep patterns were then assessed during auditory stimulation test sessions. In young rats, auditory stimulation was administered during each REM sleep bout. In old rats, auditory stimulation was administered on a fixed schedule (10 min of stimulation alternating with 15 min quiet). The day after the stimulation session, an additional sleep record (Day 2) was obtained for each rat. In young rats, auditory stimulation enhanced both REM sleep duration and total REM sleep time. In the old rats, which showed impaired sleep measures as compared to young animals, auditory stimulation enhanced both total REM sleep time and the number of REM sleep periods. Residual proactive effects of auditory stimulation (Day 2) were observed in both young and old rats. Thus, auditory stimulation is an effective manipulation with which to augment REM sleep in both young and old rats, and partially attenuates REM sleep impairments in old rats.

Bilateral pontine tegmental lesions produce in cats the phenomenon known as rapid eye movement (REM) sleep without atonia. During episodes of REM sleep without atonia cats are capable of exhibiting such complex behaviors as head-raising, body-righting, standing, and in some cases, walking and attacking. Since release of such behaviors implies disinhibition of specific motor systems, the purpose of this study was to determine whether the administration of chloramphenicol (CAP), which is known to attenuate the firing frequencies of cells that become activated during REM and motor activity, could reverse this phenomenon. Cats with dorsolateral tegmental pontine (DLTP) lesions producing REM without atonia were thoroughly studied in terms of the muscular and behavioral activity they displayed during REM before and after systemic CAP administration. Thiamphenicol (TAP), a CAP analogue that does not reduce neuronal firing frequency during REM sleep, was used as a control drug. The results of these experiments showed that CAP but not TAP induced a return of the atonia during REM sleep. It is suggested that the return of atonia induced by CAP in DLPT lesioned cats is caused by attenuation in the activity of medial reticular neurons which have somatotopical representation. Such cells, which have high levels of activity during REM sleep and motor activation in wakefulness, are normally overwhelmed by the inhibitory mechanism of the atonia of REM. The return of atonia and consequent reduction in complex behavior following CAP administration may be due to withdrawal of the excitatory influence of these neurons.

It has been shown that auditory or somatic stimulation during rapid eye movement (REM) sleep is capable of producing a significant increase in ponto-geniculo-occipital (PGO) spike density as well as in REM sleep duration. The purpose of this study was to determine the role of the medial pontine reticular formation (PRF) in mediating such increase of REM sleep duration. After a baseline recording whereby on the same recording day the control and the stimulus (auditory or somatic) alternated with each REM, a group of cats was lesioned with kainic acid in the PRF. The sleep-wake cycle was recorded again on days 15, 30 and 45 it post-lesion, following the same procedure. The results showed no changes in REM sleep duration and PGO spike density in the lesioned animals. However, when sensory stimulation was applied it was ineffective in producing REM sleep enhancement, although it was able to increase PGO spike density. These findings suggest that the effects of sensory stimulation on REM sleep duration are accomplished through the PRF, probably by inducing an increase in the excitability levels of such neurons, and further suggests that PGO spike density and REM duration are independent of each other.

It has been shown that REM sleep duration and ponto-geniculo-occipital (PGO) spike density can be enhanced by auditory stimulation. The purpose of this study was to determine whether this effect is restricted to the auditory sensory modality or whether somatic stimulation can produce similar effects. Cats implanted with electrodes for recording the sleep-wake cycle were additionally prepared with clip electrodes placed in the neck for somatic stimulation. Such stimulus was applied at the beginning and throughout each REM sleep period. The effect of this procedure was compared to a similar period when no stimulus was applied. The results showed that somatic stimulation induced a significant increase in REM duration (60.2%) and PGO spike density. Since the effects of somatic stimuli are identical to auditory ones, it is suggested that all sensory modalities may share the property of influencing the mechanisms which regulate the maintenance of REM sleep. Such mechanisms are discussed in terms of an increase in the excitability levels of polymodal medial reticular neurons.

Rats which sustained lesions of the suprachiasmatic nucleus (SCN) were transplanted with fetal hypothalamic tissue which included the SCN. After the graft, animals were kept under a 12:12 light-dark (LD) cycle during 6 weeks at which time half the animals were placed in constant light (LL) and half in constant darkness (DD). The results showed that all grafted rats recovered the photoperiod under LD, but under constant conditions rats began to free-run only in DD. The results suggest that the grafted tissue functions as a self-sustained oscillator only in darkness.

In the past few years a steadily increasing number of substances have been suggested to qualify as sleep-inducing factors. Most ‘sleep factors’ appear to exert their effects on slow-wave sleep. Recently, however, it has been shown that the cerebrospinal fluid (CSF) of sleep-deprived cats may contain a rapid eye movement (REM) sleep factor, and that vasoactive intestinal peptide (VIP) may be a specific REM sleep inducer. The purpose of this study is to determine whether the CSF of sleep-deprived cats and VIP can reverse insomnia produced by parachlorophenylalanine (PCPA). Donor cats were sleep-deprived for 24 h and their CSF extracted. Some donor cats were additionally pre-treated with chloraphenicol, and some extracted CSF was heated. Recipient cats were injected with 400 mg/kg i.p. of PCPA on two consecutive days. Twenty-four h after the second injection, the recipient cats were intraventricularly injected with a 100-μl of the various CSF types or 200 ng of VIP. The results showed that only CSF from sleep-deprived cats and VIP were capable of restoring REM sleep in the otherwise PCPA insomniac cats. Since the return of REM sleep was through an increase in its frequency, it is suggested that the CSF of sleep-deprived cats contains a VIP-like sleep factor possibly involved in triggering REM sleep.

It was previously shown that an auditory stimulus given prior to and throughout a rapid eye movement (REM) sleep period was capable of inducing a significant increase in REM sleep duration and pontogeniculo-occipital (PGO) spike density. The purpose of this study was to determine whether the increase in REM duration is dependent on PGO spike density. We administered atropine to cats at doses of 0.1-0.6 mg/kg and the effects on REM duration and PGO spikes was determined. The doses of 0.2 and 0.3 mg/kg of atropine were then utilized to compare REM sleep periods with and without auditory stimulation. The results showed that both REM duration and PGO spikes were decreased by atropine, but could be dissociated from each other depending on the doses. In addition, it was shown that the auditory stimulus protected the animals from the effects of atropine but only in relation to REM sleep duration. The results indicate that both REM sleep duration and PGO spikes have a cholinergic component and that the auditory stimulus exerts its REM enhancing properties in a manner which seems to be independent of the PGO spike density. The results are discussed in terms of receptor availability and/or excitability levels of medial reticular neurons.