Sleep Patterns In Rats Research Articles

Sleep alterations in an experimental orofacial pain model in rats

This study sought to assess sleep patterns in rats injected with Freund's adjuvant (FA) in the temporomandibular joint (TMJ) as a potential experimental orofacial pain model. Pain response to indomethacin was also assessed. Rats were implanted with electrodes to record electrocorticogram and eletromyogram signals. After a baseline (B) recording, they were injected with Freund's adjuvant (orofacial pain group, n=8) or saline (sham group, n=8) in the temporomandibular joint, and their sleep was monitored over two 12-h light periods. In the second phase of the study, after injecting Freund's adjuvant, indomethacin was administered (1 mg/kg p.o.) at 12- intervals, and sleep patterns were recorded for two additional light periods. The orofacial pain group showed a reduction in sleep efficiency during the two light periods compared with the baseline recording and with the sham group ( p<0.001). Increases in sleep and paradoxical sleep (PS) latencies of approximately 200% and 420%, respectively, were observed, as well as an increase in the number of awakenings during both periods ( p<0.001). Treatment with indomethacin increased sleep efficiency ( p<0.001) and paradoxical sleep time ( p<0.001). The number of awakenings ( p<0.001) and sleep ( p<0.001) and paradoxical sleep latencies ( p<0.001) were reduced reestablishing the normal sleep pattern. The results showed the reliability and usefulness of the temporomandibular joint pain model to characterize sleep disturbances related to pain and its response to indomethacin.

Comparative effect of Coffea cruda potencies on rats

The effects of Coffea cruda 30 and 200c and caffeine on the sleep pattern of rats were investigated. Treatments were administered orally at the beginning of the sleeping period. EEG from the parietal region was recorded. Delta (0.5–2.5 Hz) and slow (<1 Hz) waves are two of the major oscillation types that characterize neocortical electrical activity. The spectral power in these bands and the power ratio between 0.32–0.48 Hz and the delta band (slow/delta power ratio) for control and treatment groups were analyzed blind. Power in the delta band was significantly higher than baseline for Coffea 30c and caffeine (15.5 mg/kg). An increase in the slow/delta power ratio between control and treatment was detected for Coffea cruda 30 and 200c. Coffea 30c and caffeine have similar effects on sleep pattern, enhancing delta power; Coffea cruda 200c appears to affect only the synchronization.

Homoeopathic effect on the sleep pattern of rats

The effect of Nux vomica on the EEGs of rats during sleep was quantified in terms ofsuitable statistical parameters that showed systematic changes after the homoeopathic stimulus. Our results are consistent with a decrease in the coherence of the brain signal compared to results obtained by using either the solvent on its own or pure water, and can be interpreted in terms of irritation of the animals' central nervous system due to the applied stimulus. This coincides with the effect Nux vomica has on healthy humans and suggests a means of characterizing the homoeopathic effect in physicochemical terms, based on parameters similar to those found appropriate in this study, calculated for physiological data from animal models for specific conditions. It also lends scientific support to ongoing attempts to extend Hahnemann's principles of similitude and potentiation beyond their original context, into the realm of veterinary medicine.

Bromocriptine-lnduced Blockade of Pregnancy Affects Sleep Patterns in Rats

We previously reported a marked enhancement of nocturnal sleep in pregnant and pseudopregnant rats and suggested a possible involvement of prolactin (PRL) in the modulation of sleep during pregnancy. In the present study, the release of PRL was blocked by a dopamine agonist, bromocriptine (CB-154), and time-course changes in sleep were analyzed in pregnant rats. After pregnancy was induced by fertile mating with males (Day 1), rats (n = 5) were injected with 1 mg of CB-154 subcutaneously 3 h before the onset of darkness for a 3-day period (Days 1-3 or 6-8). Electroencephalogram and electromyogram for evaluating the state of sleep and wakefulness were monitored continuously up to the reappearance of an estrous cycle in the treated rats. The CB-154 treatment resulted in abortion in all rats and suppressed the pregnancy-associated nocturnal increase in non-rapid-eye-movement sleep (NREMS) and rapid-eye-movement sleep (REMS). The CB-154 treatment also decreased the diurnal amount of NREMS significantly. The sleep-suppressing effect of CB-154 on Days 6-8 was induced more promptly than that on Days 1-3. In the night of proestrus following the termination of pregnancy (Day 4 or Day 12), both NREMS and REMS decreased to the baseline level observed at prepregnant proestrus. Thus, our results indicated that CB-154 neutralized the pregnancy-associated sleep changes, which might be due to the inhibition of the PRL release. It is suggested that PRL is at least partially responsible for the regulation of sleep during pregnancy.

The role of the habenula-interpeduncular pathway in modulating levels of circulating adrenal hormones

The fasciculus retroflexus (FR) is the major pathway by which the medial and lateral habenular nuclei project to the interpeduncular nucleus (IPN) and ventral tegmentum. Recent work has suggested that the habenula-interpeduncular system may be involved in the regulation of states of arousal. Bilateral FR lesions have been shown to disrupt chronically, and habenula transplants have been shown to restore normal sleep patterns in rats [J. NeuroscL, 12 (1992) 3282-3290]. In this study, we examined whether FR lesions and habenula cell transplants would also modify chronically the circulating plasma levels of the stress-related hormones, norepinephrine (NE), epinephrine (EPI) and corticosterone. When plasma samples were obtained via retro-orbital eye-bleed during anesthesia, animals with FR lesions had significantly increased levels of plasma NE, EPI and corticosterone 2-3 months postoperatively compared to unoperated controls. Transplants of embryonic habenula cells placed near the denervated IPN in FR-lesioned animals restored levels of NE and EPI to normal, but did not attenuate elevated corticosterone levels. When plasma samples were obtained in conscious animals via indwelling arterial cannulae, FR-lesioned rats likewise exhibited increased basal levels of corticosterone but plasma levels of catecholamines were similar to those of unoperated controls. Differences in our results obtained using the two methods of blood sampling may be explained by the effects of anesthesia and stress associated with the eye-bleed method. Thus, the effect of FR lesions in increasing plasma levels of catecholamines may not reflect a difference in basal hormone levels, but a heightened sympathetic adrenomedullary response to stress. While these results indicate that the integrity of the habenular efferent pathway is important in modulating circulating levels of hormones associated with the stress response, two separate mechanisms appear to control its interactions with sympathetic-adrenal medullary and adrenocortical pathways.

Effects of [des-Tyr-D-Phe 3]beta-casomorphin (2–5) on sleep pattern in rats

The effects of the antidepressant-like acting peptide [des-Tyr-D-Phe 3]beta-casomorphin(2–5) (Pro-D-Phe-Pro-Gly, BCH-325) on sleep were studied in rats. The rats received subcutaneous injections of BCH-325 in acute experiments (doses: 4, 20, 100, 500 and 2500 nmol/kg) and in a 10-day chronic experiment (50 nmol/kg/day). Acute administration of 20 and 100 nmol/kg enhanced wakefulness, 500 and 2500 nmol/kg enhanced paradoxical sleep, and 4 nmol/kg had no effect. Chronic administration resulted in an increase of paradoxical sleep during the first 5 days of drug treatment. Thus the sleep effects of BCH-325 differ from those of typical antidepressants and other psychotropic drugs.

Melatonin modulates the sensitivity of 5-hydroxytryptamine-2 receptor-mediated sleep—wakefulness regulation in the rat

The interaction between melatonin and two 5-hydroxytryptamine (5-HT 2) compounds was studied on sleep patterns in rats. Administration of the 5-HT 2 receptor antagonist ritanserin (0.63 mg/kg, i.p.) resulted in a significant increase of deep slow wave sleep (SWS2) and a decrease of paradoxical sleep (PS). The 5-HT 2 receptor agonist DOM (1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane) (0.63 mg/kg, i.p.) produced a significant reduction of both SWS2 and PS. Melatonin (1 mg/kg, i.p.) alone did not alter sleep but counteracted the sleep effects induced by ritanserin as well as DOM. It is proposed that melatonin modulates the sensitivity of 5-HT 2 receptor-mediated sleep response probably by an indirect route.

Differential effects of acetylsalicylic acid and acetaminophen on sleep abnormalities in a rat chronic pain model

We studied the effects of two non-steroidal anti-inflammatory analgesics (NSAIAs), acetylsalicylic acid (ASA) and acetaminophen, on sleep patterns in rats with adjuvant-induced arthritis. We found that in the normal rat both NSAIAs reduced non-rapid eye movement (NREM) sleep. In arthritic rats ASA and acetaminophen had opposite effects on sleep. ASA increased wakefulness and decreased all sleep stages and acetaminophen decreased wakefulness and increased NREM sleep and paradoxical sleep during the light hours (the hours of maximal sleep in the normal rat). When the effects of severity of arthritis were factored out, both drugs still had large and significant effects on sleep and wakefulness. Thus, two prostaglandin synthetase inhibitors showed differential effects on sleep and wakefulness in the normal rat and in rats experiencing chronic pain. Although ASA is important in the treatment of pain in rheumatic diseases, it may contribute to abnormal sleep patterns.

Effects of kynurenic acid and ketamine on neonatal sleep in rats.

Kynurenic acid and ketamine are, besides non-specific actions, antagonists of excitatory acidic amino acids in the rat brain. At intraperitoneal doses of 300 mg/kg (1.6 mmol/l) and 5 mg/kg (18 mmol/l), respectively, they are equipotent antagonists of N-methyl-D-aspartate receptors. We studied the acute effects of ketamine and kynurenic acid, at these doses, on sleep patterns of rats during the second and third postnatal weeks with the so called static charge sensitive mattress (SCSB). Both kynurenic acid and ketamine decreased active sleep; ketamine additionally increased quiet state and kynurenic acid increased waking. The decrease in active sleep may be related to glutaminergic NMDA and serotonergic responses in the rat brain but non-specific actions and interactions with other transmitter systems are also involved.

Effects of clonidine and BS 100–141 on the EEG sleep pattern in rats

The effects of the peripheral and central α-adrenoceptor stimulant and antihypertensive agents clonidine and BS 100–141 (N-amidino-2[2,6-dichlorophenyl]acetamide · HCl) on EEG sleep patterns in rats and on blood pressure in pithed rats have been investigated. Whereas both compounds abolished paradoxical sleep (PS), clonidine, in contrast to BS 100–141, markedly increased the sleeping time. Both drugs caused a dose-dependent increased in the blood pressure of pithed rats. The pressor action was abolished by the α-adrenoceptor blocking agent phentolamine, but was not influenced by reserpine, indicating a direct stimulation of vascular α-adrenoceptors by both drugs. It is suggested that sedation or sleep induction by adrenergic drugs cannot be explained exclusively by an action on central α-adrenoceptors. Rather, the findings suggest that such an action may be involved in the modulation of PS.

Individual (constitutional) differences in sleep patterns in rats

Individual (constitutional) differences in sleep patterns in rats