Sleep and wakefulness in the green iguanid lizard (Iguana iguana).

The reptile Iguana iguana exhibits four states of vigilance: active wakefulness (AW), quiet wakefulness (QW), quiet sleep (QS) and active sleep (AS). Cerebral activity decreases in amplitude and frequency when passing from wakefulness to QS. Both parameters show a slight increase during AS. Heart rate is at a maximum during AW (43.8+/-7.9 beats/min), decreases to a minimum in QS (25.3+/-3.2 beats/min) and increases in AS (36.1+/-5.7 beats/min). Tonical and phasical muscular activity is present in wakefulness, decreases or disappears in QS and reappears in AS. Single or conjugate ocular movements are observed during wakefulness, then disappear in QS and abruptly reappear in AS. Although these reptiles are polyphasic, their sleep shows a tendency to concentrate between 20:00 and 8:00 h. Quiet sleep occupies the greater percentage of the total sleep time. Active sleep episodes are of very short duration, showing an average of 21.5+/-4.9 (mean+/-SD). Compensatory increment of sleep following its total deprivation was significant only for QS. Reaction to stimuli decreased significantly when passing from wakefulness to sleep. It is suggested that the lizard I. iguana displays two sleep phases behaviorally and somatovegetatively similar to slow wave sleep and paradoxical sleep in birds and mammals.

Topographical distribution of the locus coeruleus and raphe nuclei in the lizard Ctenosaura pectinata: functional implications on sleep.

The nature of sleep in reptiles has traditionally created intense discussion and has originated some controversy. Nevertheless, some authors have described a sleep phase analogous to sleep in endotherm vertebrates. It is known that in mammals, the locus coeruleus and raphe nuclei, located in the brain stem, are functionally related to the sates vigilance regulation. In contrast the presence of two sleep phases in the lizard Ctenosaura pectinata similar to slow wave sleep and rapid eye movement sleep have been described. Therefore we carried out studies of the brain stem of C. pectinata to search for cellular groupings related to the regulation of these sleep phases. We identified and described the topographical distribution of the locus coeruleus and raphe nuclei in the lizard C. pectinata. Results show that these nuclei that have been functionally related to vigilance states in mammals, are also present in C. pectinata. These nuclei are formed by fairly well defined cellular groupings placed in the brain stem.

Sleep characteristics in the turkey Meleagris gallopavo.

Electrophysiological and behavioral characteristics of the states of vigilance were analyzed in chronically implanted specimens of the turkey Meleagris gallopavo (M. gallopavo). Five different states of vigilance were observed throughout the nyctohemeral period: active wakefulness (AW), quiet wakefulness (QW), drowsiness (D), slow wave sleep (SWS) and rapid eye movement (REM) sleep. These states exhibit characteristics similar to those described in other bird species. Sleep periods displayed a polyphasic distribution; however, they showed the tendency to concentrate between 2100 and 0900 h in spite of the fact that the recordings were carried out under constant illumination. Sleep period occupied 45.71% of the nyctohemeral cycle, 43.33% corresponded to SWS, while 2.38% to REM sleep. The average duration of the REM sleep phase was very short, lasting 7.7+/-0.55 s (mean+/-S.D.). In contrast, its frequency was very high with an average recurrence of 268+/-63 phases throughout the nyctohemeral cycle. The short duration of REM sleep phase presented by the turkey as by other bird species studied up to now may be dependent upon genetic factors shared by this group of vertebrates.

Sleep patterns of the volcano mouse (Neotomodon alstoni alstoni).

Sleep-waking patterns of the volcano mouse were studied under laboratory conditions. This rodent exhibits four states of vigilance: active wakefulness (Aw), quiet wakefulness (Qw), slow-wave sleep (SWS), and paradoxical (PS), or rapid-eye movement (REM) sleep. These states present, in general, the classic mammalian electrophysiological patterns. Although sleep periods were distributed at any time of the nychthemeral cycle, they showed the tendency to concentrate between 0800 and 2000 hours. The volcano mouse may be considered as a "good" sleeper, because it shows a relatively high percentage of sleep from the total recording time (TRT). Slow-wave sleep occupied 64.54 +/- 8.84% (mean +/- SD) of the total recording time, while 7.56 +/- 1.31% corresponded to rapid-eye movement sleep. The average duration of the rapid-eye movement sleep phase was 126.48 +/- 17.79 s, exhibiting an average recurrence of 49 +/- 9.28 phases throughout the nychthemeral cycle. Mean duration of the sleep cycle was 9.23 +/- 2.36 min. Quantitative data of the volcano mouse sleep may be considered adequate for its body size and characteristic of an animal which sleeps in secure places under free-living conditions.

Effect of p-chlorophenylalanine (PCPA) on sleep and monoamines content in the brain of a lizard species.

Administration of PCPA, a specific inhibitor of serotonin synthesis, induced a significant decrease of total sleep time in the lizard Ctenosaura pectinata. This effect was exerted on both quiet sleep and active sleep, but it was more intense on active sleep. Reduction in the amount of active sleep was due to a decrease in the number of the episodes not in their mean duration, since this parameter increased significantly from 5.97 s, under control conditions, to 11.77 s, 10.66 s and 8.85 s at 24, 48 and 72 h after PCPA injection, respectively. Neurochemical analysis showed a significant decrease in the amount of serotonin in the analyzed brain stem structures 12 h after PCPA administration. The possible participation of serotonergic mechanisms in the regulation of reptilian sleep is discussed.

Cerebral death induced by electrical current.

Application of a 126 V, 3 Ampers electrical current produces brain death in dogs assessed by irreversible installation of an isoelectric electroencephalogram. Cerebral death was immediate or preceded by a paroxistic activity of short duration (25 +/- 12 Seconds; Mean +/- SD). Besides the isoelectric electroencephalogram, there were immediate respiratory arrest and cardiac fibrillations followed by heart stopping. Reflexes were absent and no response to painful stimuli was observed. An appropriate utilization of the experimental method described in this study may contribute to improve the knowledge about the pathophysiology of cerebral death in humans.

Ketamine antagonizes toxic action of anticholinesterase agents.

Ketamine is an anaesthetic interacting with several neurotransmitters. Among others, ketamine exerts some cholinergic actions (ACh). This paper presents the results of studying the interaction of ketamine with ACh in two animal species. Atropine slightly increased the time of immobility produced by ketamine injections in rats. Meanwhile, neostigmine slightly decreased such immobility. Ketamine resulted similar in behavioral actions and shared some electroencephalographic (EEG) actions of scopolamine in cats. The most striking interaction consisted on an antagonism of ketamine on the action of anticholinesterase agents. In both species, ketamine blocked the EEG and the behavioral toxic effects of neostigmine and physostigmine. Notwithstanding, the anticholinesterase agents were unable in reducing the actions of ketamine. This partial cholinergic agonist action of ketamine support certain but limited use of the anesthetic against insecticidal anticholinesterase poisoning.

Projections of the nucleus accumbens in the cat.

Due to the recent advances in knowledge on the function of the limbic system it would be wise to consider this system as being widely distributed throughout the diencephalic and mesencephalic levels as well as the forebrain. Numerous regions have been discovered that are related to the limbic structures in anatomical and functional respects. According to Koikegami et al. (1967), it would be adequate to divide this system into two main categories--the major limbic rim or the structure proper and the paralimbic structures. The former defined phylogenetically and ontogenetically as those structures around the third ventricle such as: the hippocampus, septum, dentate gyrus, fimbria hippocampi, anterior and posterior cingulate gyri, area paraolfactoria, amygdala and Diagonal Band of Broca. The paralimbic structures may represent those brain regions, which have direct connections or functional correlations with the limbic formation proper. These areas include the posterior orbital gyrus, insula, nucleus accumbens, head of the caudate, nucleus habenula, nucleus interpendencularis, nucleus pulvinaris thalami, intralaminar and anterior thalamic nucleus, preoptic area, hypothalamic nuclei, mammillary body, subthalamus, limbic midbrain area of Nauta, temporal lobe pole, superior temporal gyrus, praecuneus, nucleus dorsalis et profundis tegmenti of Gudden and claustrum. In the present paper we will deal with the projections of the nucleus accumbens. This nucleus was described by Meynert (1872) as the anterior polar region of the caudate nucleus. Kappers describes the nucleus accumbens in 1908 as the nucleus accumbens septi and considers it as a part of the striatum. Later on, the histological studies of Brochaus (1942) relate a part of the nucleus with olfactory functions, and he describes another part, which is very well developed in microsmatic mammals and in anosmic mammals like the dolphin. Szteyn (1960) describes two main areas, the accumbens septi and the accumbens caudate. Nevertheless, the accumbens constitutes a very important region of the paralimbic system and seems to play an important role in some behavioral patterns.

Lateralization of spike and wave complexes produced by hallucinogenic compounds in the cat.

The ability of four hallucinogenic compounds--ketamine, phencyclidine, quipazine, and SKF-10 047--to produce some specific electrical pattern in portions of the limbic system and the hemispheric lateralization of such effects were studied in cats with permanently implanted electrodes. Electronic frequency and area integrators were used to analyze the results, and the percentage change in electrographic alterations was calculated. All compounds studied produced trains of spike and wave complexes in the cingulum, rapid discharges in the amygdala complex, and slow-wave synchronous activity in the septal nucleus. Those changes predominated in the left hemisphere. At small but hallucinatory concentrations of these drugs, the cortical EEG was not affected. Exploratory movements directed toward nonexistent objects, classified as hallucinatory-like behavior, appeared simultaneous with these changes in the EEG recordings. We concluded that there could exist a relationship between the appearance of spike and wave complexes in the limbic system without epileptic signs (twitching or myoclonus) and the presence of hallucinations, and that there is a left side hemispheric lateralization of the electrographic effects, viewing cerebral dominance phenomena as a functional and fluctuating state.

Interhemispheric changes in alpha rhythm related to time perception.

Each cerebral hemisphere processes environmental information in a different but complementary manner. Structures located in the left hemisphere are assumed to participate in symbolic-logic thinking. Time perception may be considered among such thinking processes. The present study evaluates bilateral occipito-central EEG activity in healthy, right-handed subjects which was produced while they performed a visuomotor monitoring task. The task consisted of two stages. The first stage involved the subject's learning a fixed time interval (10 sec) and the measurement of their reaction time. Subjects responded to an isolated light stimulus by pressing a button with the dominant hand. In the second stage, the subjects accuracy in estimating interval-length was evaluated. Two forms of EEG analysis were used, frequency and alpha ratio, each of which was measured both prior to and subsequent to the motor response. A reversal group was used to carry out a complementary test. Subjects responded in the first block of experiments with the non-dominant (left) hand and with the dominant hand in the second. Results showed that left hemisphere activity was continuous during the interval-learning stage and with optimal reaction times and remained continuous when estimation values approximated the real interval. In addition, in optimal reaction time and near to optimal time estimation responses, the left side showed lower frequency and alpha ratio than did the right. Finally a progressive enhancement in both parameters from the right hemisphere was related to deterioration in test performance. Results from the reversal group did not differ from those of the first group. As evaluated by gross measurements of the EEG, a predominant participation of the left hemisphere in time processing is concluded.

Spike and wave complexes produced by four hallucinogenic compounds in the cat.

The ability of four hallucinogenic compounds: ketamine, phencyclidine, quipazine and SKF-10,047 to produce spike and wave activity in the limbic system, was studied in cats with permanently implanted electrodes. Electronic frequency integrators were used to analyze the results and the percent of change in electrographic alterations was calculated. All the compounds studied, produced trains of 6/sec spike and waves complexes in the cingulum, rapid synchronous discharges in the amygdaloid complex, and slow wave synchronous activity and spiking in the septal areas. At low but hallucinatory concentrations of these drugs, the cortical EEG was not affected. Exploratory movements directed toward non-existent objects, classified as hallucinatory-like behavior, appeared simultaneous with these changes in the EEG recordings. It was concluded that there could exist a relationship between the appearance of 6/sec spike and wave complexes in the cingulum and the presence of hallucinations, produced by some synthetic drugs in the cat, this activity could be interpreted as the spreading of altered function of limbic and non-limbic nuclei related with this bundle which explain unspecificity of action.