Rat brain opioid peptides-circadian rhythm is under control of melatonin.

Several experiments have revealed an Endogenous Opioid System (EOS)-circadian rhythm. The brain-borne hormone, melatonin (MEL) has been shown to regulate the organism photoperiodic activity and may be implicated in the EOS-circadian rhythm. To explore this hypothesis, we studied the effect of functional pinealectomy on the EOS-circadian rhythm by measuring the immunoreactive content of Met-Enkephalin, Leu-Enkephalin and Synenkephalin in both hypothalamus and hippocampus of the rat brain, using standard radioimmunoassay procedures. Experimental animals exposed to white fluorescent light (WFL) for 15days (<50lux), displayed a disruption of the EOS-circadian rhythm, showing that absence of MEL induced a significant decrease of tissue content of enkephalin peptides at 01:00h during the dark-phase of the 24-h circadian rhythm, when compared to control rats. Functional pinealectomized rats exposed to 4 or 6h period of darkness (used to revert the effects induced by the absence of melatonin) significantly increased the tissue content of ME-IR and LE-IR, when compared to both controls and non-exposed WFL-treated rats. In addition, subcutaneous administration of exogenous melatonin (10, 100, 150, 300, 600microg/kg), in WFL-treated animals produced significant dose-dependent increases of ME-IR in both brain regions tested. Finally, luzindole (melatonin receptor antagonist) administration, was not able to prevent the enkephalin tissue increase, induced with the MEL administration (150microg/kg). This data suggest that MEL not only regulates the EOS-circadian rhythm, but also appears to modulate their synthesis in the rat brain from their respective neurons.

The menstrual cycle of the spider monkey (Ateles geoffroyi).

The ovarian cycles of four adult female spider monkeys (Ateles geoffroyi) were followed daily throughout 30 days by means of vaginal swabs and blood samplings. Cytological analyses of the vaginal swabs and radioimmunoassay determination of the daily levels of estradiol-17 beta (E2) and progesterone (P4) wer done in order to classify the kind of ovarian cycle of this species. Our results show that Ateles geoffroyi females display menstrual cycles of about 24 days on average. By comparison with the well-known menstrual cycles of women, apes, and Old World monkeys, the four distinctive cytological phases (bleeding, follicular, periovulatory, and luteal) could be recognized; mid-cycle E2 peaks followed by mid-luteal increases of the same hormone were present in all four females. P4 levels were higher after the E2 peak, although both hormones were present throughout the cycles. Also, age-dependent features, hormone profiles, and changes in menstrual phases lengths were detected.

Self and Social Grooming in Stump-Tailed Macaques: Effects of Kin Presence or Absence within the Group.

The relation between individual self and social-grooming scores, asaessingthe effects of having or lacking relatives within the group, was studied in a colony of stump-tailed macaques (Macacaarctoides). As it has been shown by other authors, kinship favoured grooming interactions, so animals lacking relatives wen seldom mom as groomees. Conversely, these subjects accounted for the major mounts of self-grooming, as if they were surmounting the social grooming deficit. This negative relationship between self and social grooming suggests a common functional relationship between both forms of behavior, most likely as a reducing tension activity.

Social structure features in three inbred strains of mice, C57Bl/6J, Balb/cj, and NIH: a comparative study.

Some features of social living were investigated in three inbred strains of mice: C57Bl/6j, Balb/cj, and NIH. Five social behaviors--Aggression, Submission, Allogrooming, Social Rest and Rest Alone, as well as Wheel Running Activity--were recorded 2 h daily for a week, in 26 groups of seven male mice living in an enriched environment. Dominants and subordinates among strains shared some behavioral characteristics, but strain contributions upon social structure were also detected. Similarities among strains included the appearance of a single dominant mouse per group rated as the most aggressive, besides from being the animal presented with most Submissions. Allogrooming was more frequent among subordinates than among dominants and subordinates. Differences among strains were that agonistic behavior among subordinates was higher in the Balb/cj and NIH groups than in the C57Bl/6j mice. NIH mice were recorded in Rest Alone more often than mice from the other strains. C57Bl/6j dominants showed higher rates of Wheel Running Activity than subordinates.

Psychopharmacologic analysis of an alleged oneirogenic plant: Calea zacatechichi.

Calea zacatechichi is a plant used by the Chontal Indians of Mexico to obtain divinatory messages during dreaming. At human doses, organic extracts of the plant produce the EEG and behavioral signs of somnolence and induce light sleep in cats. Large doses elicit salivation, ataxia, retching and occasional vomiting. The effects of the plant upon cingulum discharge frequency were significantly different from hallucinogenic-dissociative drugs (ketamine, quipazine, phencyclidine and SKF-10047). In human healthy volunteers, low doses of the extracts administered in a double-blind design against placebo increased reaction time and time-lapse estimation. A controlled nap sleep study in the same volunteers showed that Calea extracts increased the superficial stages of sleep and the number of spontaneous awakenings. The subjective reports of dreams were significantly higher than both placebo and diazepam, indicating an increase in hypnagogic imagery occurring during superficial sleep stages.

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.