The role of nitric oxide in reproduction

Nitric oxide (NO) plays a crucial role in reproduction at every level in the organism. In the brain, it activates the release of luteinizing hormone-releasing hormone (LHRH). The axons of the LHRH neurons project to the mating centers in the brain stem and by afferent pathways evoke the lordosis reflex in female rats. In males, there is activation of NOergic terminals that release NO in the corpora cavernosa penis to induce erection by generation of cyclic guanosine monophosphate (cGMP). NO also activates the release of LHRH which reaches the pituitary and activates the release of gonadotropins by activating neural NO synthase (nNOS) in the pituitary gland. In the gonad, NO plays an important role in inducing ovulation and in causing luteolysis, whereas in the reproductive tract, it relaxes uterine muscle via cGMP and constricts it via prostaglandins (PG).

Changes in the behavioral and immunological parameters of the mollusk Biomphalaria tenagophila induced by disruption of the circadian cycle as a consequence of continuous illumination

In the present investigation we studied some behavioral and immunological parameters of adult gastropod mollusk, Biomphalaria tenagophila, which have been reproducing for several generations under laboratory conditions. One group of gastropods was kept on a 14-h light/10-h dark cycle, corresponding to a regular circadian cycle, and another group was exposed to continuous light for 48 h. Animals were studied along (behavioral groups) or immediately after (immunological groups) 48 h of regular circadian cycle or continuous light conditions. Stopping/floating, dragging and sliding were the behavioral aspects considered (N = 20 for regular cycle; N = 20 for continuous illumination) and number of hemocytes/µl hemolymph was the immunological parameter studied (N = 15 for regular cycle, N = 14 for continuous illumination). Animals under continuous illumination were more active (sliding = 33 episodes, dragging = 48 episodes) and displayed a lower number of hemocytes (78.0 ± 24.27/µl) when compared with mollusks kept on a regular circadian cycle (sliding = 18 episodes, dragging = 27 episodes; hemocytes = 157.6 ± 53.27/µl). The data are discussed in terms of neural circuits and neuroimmunological relations with the possible stressful effect of continuous illumination.

Behavioral and electroencephalographic analysis of seizures induced by intrahippocampal injection of granulitoxin, a neurotoxic peptide from the sea anemone Bunodosoma granulifera

In this study, the behavioral and electroencephalographic (EEG) analysis of seizures induced by the intrahippocampal injection in rats of granulitoxin, a neurotoxic peptide from the sea anemone Bunodosoma granulifera, was determined. The first alterations occurred during microinjection of granulitoxin (8 µg) into the dorsal hippocampus and consisted of seizure activity that began in the hippocampus and spread rapidly to the occipital cortex. This activity lasted 20-30 s, and during this period the rats presented immobility. During the first 40-50 min after its administration, three to four other similar short EEG seizure periods occurred and the rats presented the following behavioral alterations: akinesia, facial automatisms, head tremor, salivation, rearing, jumping, barrel-rolling, wet dog shakes and forelimb clonic movements. Within 40-50 min, the status epilepticus was established and lasted 8-12 h. These results are similar to those observed in the acute phase of the pilocarpine model of temporal lobe epilepsy and suggest that granulitoxin may be a useful tool not only to study the sodium channels, but also to develop a new experimental model of status epilepticus.

Behavioral correlates of the activity of serotonergic and non-serotonergic neurons in caudal raphe nuclei

We investigated the behavioral correlates of the activity of serotonergic and non-serotonergic neurons in the nucleus raphe pallidus (NRP) and nucleus raphe obscurus (NRO) of unanesthetized and unrestrained cats. The animals were implanted with electrodes for recording single unit activity, parietal oscillographic activity, and splenius, digastric and masseter electromyographic activities. They were tested along the waking-sleep cycle, during sensory stimulation and during drinking behavior. The discharge of the serotonergic neurons decreased progressively from quiet waking to slow wave sleep and to fast wave sleep. Ten different patterns of relative discharge across the three states were observed for the non-serotonergic neurons. Several non-serotonergic neurons showed cyclic discharge fluctuations related to respiration during one, two or all three states. While serotonergic neurons were usually unresponsive to the sensory stimuli used, many non-serotonergic neurons responded to these stimuli. Several non-serotonergic neurons showed a phasic relationship with splenius muscle activity during auditory stimulation. One serotonergic neuron showed a tonic relationship with digastric muscle activity during drinking behavior. A few non-serotonergic neurons exhibited a tonic relationship with digastric and/or masseter muscle activity during this behavior. Many non-serotonergic neurons exhibited a phasic relationship with these muscle activities, also during this behavior. These results suggest that the serotonergic neurons in the NRP and NRO constitute a relatively homogeneous population from a functional point of view, while the non-serotonergic neurons form groups with considerable functional specificity. The data support the idea that the NRP and NRO are implicated in the control of somatic motor output.

Acute buspirone abolishes the expression of behavioral dopaminergic supersensitivity in mice

Previous studies have shown that rats withdrawn from long-term treatment with dopamine receptor blockers exhibit dopaminergic supersensitivity, which can be behaviorally evaluated by enhanced general activity observed in an open-field. Recently, it has been reported that co-treatment with the non-benzodiazepine anxiolytic buspirone attenuates the development of haloperidol-induced dopaminergic supersensitivity measured by open-field behavior of rats. The aims of the present study were: 1) to determine, as previously reported for rats, if mice withdrawn from long-term neuroleptic treatment would also develop dopaminergic supersensitivity using open-field behavior as an experimental paradigm, and 2) to examine if acute buspirone administration would attenuate the expression of this behavioral dopaminergic supersensitivity. Withdrawal from long-term haloperidol treatment (2.5 mg/kg, once daily, for 20 days) induced a significant (30%) increase in ambulation frequency (i.e., number of squares crossed in 5-min observation sessions) but did not modify rearing frequency or immobility duration in 3-month-old EPM-M1 male mice observed in the open-field apparatus. Acute intraperitoneal injection of buspirone (3.0 and 10 but not 1.0 mg/kg, 12-13 animals per group) 30 min before open-field exposure abolished the increase in locomotion frequency induced by haloperidol withdrawal. These data suggest that the open-field behavior of mice can be used to detect dopaminergic supersensitivity, whose expression is abolished by acute buspirone administration.

Reproductive experience influences grooming behavior during pregnancy in rats

The pregnancy-induced increase in self-licking observed in rats is important for mammary gland development and lactation. Reproductive experience has epidemiologial implications such as a decrease in the incidence of mammary gland cancer in women and it also influences various behavioral, neurochemical and endocrine parameters. The aim of the present study was to investigate the influence of reproductive experience on grooming behavior patterns during pregnancy in rats. Self-grooming behavior was measured in age-matched virgin, primi- and multigravid (days 7, 8, 9, 19, and 20 of pregnancy) rats. General grooming (head, forelimbs and shoulders) was not significantly different among virgin, primi- and multigravid rats during pregnancy. Confirming previous work, pregnant rats spent significantly more time in specific grooming (mammary glands, nipple lines, genital and pelvic regions) than did virgin animals. In addition, self- licking of mammary glands was significantly increased in multi- as compared to primigravid rats on days 8, 9, 19 and 20 of pregnancy. The increase in mammary gland grooming observed in multigravid rats appears to be a consequence of previous reproductive experience. These data show that reproductive experience modulates mammary gland grooming during pregnancy, possibly contributing to successful reproduction.

Evaluation of behavioral states among morning and evening active healthy individuals

The Horne-Östberg questionnaire partly covers some factors that may be important determinants of peak time and characterize patterns of behavior. We conducted a study for the evaluation of self-reported behavioral states (hunger sensation, availability for study, physical exercise, solving daily problems, and time preferences) as expressions of underlying cyclic activity. Three hundred and eighteen community subjects without history of medical, psychiatric, or sleep disorders were evaluated in a cross-sectional design. A self-report about daily highest level of activity was used to categorize individuals into morning, evening, and indifferently active. Time-related behavioral states were evaluated with 23 visual analog questions. The responses to most analogic questions were significantly different between morning and evening active subjects. Logistic regression analysis identified a group of behaviors more strongly associated with the self-reported activity pattern (common wake up time, highest subjective fatigue, as well as wake up, bedtime, exercise and study preferences). These findings suggested that the patterns of activity presented by normal adults were related to specific common behavioral characteristics that may contribute to peak time.

Behavioral characteristics of the offspring of adolescent rats

The aim of this study was to test the hypothesis that, during adulthood, the offspring of adolescent rats differ in emotionality, learning and memory from the offspring of adult rats. The behavior of the offspring of adolescent (age, 50-55 days) and adult rats (age, 90-95 days) was tested in the open field, activity cage, and passive and active avoidance apparatus. The latencies during training and testing in the passive avoidance apparatus of the offspring of adolescent parents were shorter than the latencies of control offspring (P<0.001 on both training and testing days). Offspring of adolescent parents showed shorter latency time in acquisition trials during active avoidance testing compared to control offspring (P<0.001). They also showed a higher number of active avoidance responses in the last four blocks of acquisition (P<0.001) and first two blocks of extinction trials (P<0.05 and P<0.001, respectively). The offspring of adolescent parents showed higher latency on the first day of testing in the open field (P<0.01) and a lower latency on the third day of testing (P<0.01). They also showed higher activity during all three days of testing (1st and 2nd day: P<0.01; 3rd day: P<0.05). The spontaneous activity of the offspring of adolescent parents in the activity cage was higher in the last three intervals of testing (P<0.001). In summary, the offspring of adolescent parents were less anxious and tended to be more active. The results of two learning and memory tests were opposite, but could be explained by a higher exploratory drive of the offspring of adolescent parents. This was probably due to chronic malnutrition stress and the disturbed mother-infant relationship in the litters of adolescent mothers.

Behavioral modulation by mutilation pictures in women

Previous studies have shown that women are more emotionally expressive than men. It is unclear, however, if women are also more susceptible to the emotional modulation of behavior imposed by an affective stimulus. To investigate this issue, we devised a task in which female subjects performed six sequential trials of visual target detection following the presentation of emotional (mutilation and erotic) or neutral pictures (domestic utensils and objects) and compared the data obtained in the present study with those described in a previous study with male subjects. The experiment consisted of three blocks of 24 pictures and each block had an approximate duration of 4 min. Our sample consisted of 36 subjects (age range: 18 to 26 years) and each subject performed all blocks. Trials following the presentation of mutilation pictures (283 ms) had significantly slower reaction times than those following neutral (270 ms) pictures. None of the trials in the "pleasant block" (271 ms) was significantly different from those in the "neutral block". The increase in reaction time observed in the unpleasant block may be related in part to the activation of motivational systems leading to an avoidance behavior. The interference effect observed in this study was similar to the pattern previously described for men. Thus, although women may be more emotionally expressive, they were not more reactive to aversive stimuli than men, as measured by emotional interference in a simple reaction time task.

Environmental color affects Nile tilapia reproduction

We investigated the effects of environmental color on the reproductive behavior of Nile tilapia, Oreochromis niloticus. Two environmental colors were tested by covering the aquarium (60 x 60 x 40 cm) with white (12 groups) or blue (13 groups) cellophane and observing reproductive behavior in groups of 2 males (10.27 ± 0.45 cm) and 3 females (10.78 ± 0.45 cm) each. After assignment to the respective environmental color (similar luminosity = 100 to 120 Lux), the animals were observed until reproduction (identified by eggs in the female's mouth) or up to 10 days after the first nest building. Photoperiod was from 6:00 h to 18:00 h every day. Food was offered in excess once a day and water quality was similar among aquaria. Daily observations were made at 8:00, 11:00, 14:00 and 17:00 h regarding: a) latency to the first nest, b) number of nests, c) gravel weight removed (the male excavates the nest in the bottom of the aquarium), d) nest area, and e) mouthbrooding incubation (indication of reproduction). The proportion of reproducing fish was significantly higher (6 of 13) in the group exposed to the blue color compared the group exposed to the white color (1 of 12; Goodman's test of proportions). Moreover, males under blue light removed significantly larger masses of gravel (blue = 310.70 ± 343.50 g > white = 130.38 ± 102.70 g; P = 0.01) and constructed wider nests (blue = 207.93 ± 207.80 cm² > white = 97.68 ± 70.64 cm²; P = 0.03) than the control (white). The other parameters did not differ significantly between light conditions. We concluded that reproduction in the presence of blue light was more frequent and intense than in the presence of white light.

Social condition affects hormone secretion and exploratory behavior in rats

Studies of behavior, endocrinology and physiology have described experiments in which animals housed in groups or in isolation were normally tested individually. The isolation of the animal from its group for testing is perhaps the most common situation used today in experimental procedures, i.e., there is no consideration of the acute stress which occurs when the animal is submitted to a situation different from that it is normally accustomed to, i.e., group living. In the present study, we used 90 male 120-day-old rats (Rattus norvegicus) divided into 5 groups of 18 animals, which were housed 3 per cage, in a total of 6 cages. The animals were tested individually or with their groups for exploratory behavior. Hormones were determined by radioimmunoassay using specific kits. The results showed statistically significant differences between testing conditions in terms of behavior and of adrenocorticotrophic hormone (ACTH: from 116.8 ± 15.27 to 88.77 ± 18.74 when in group and to 159.6 ± 11.53 pg/ml when isolated), corticosterone (from 561.01 ± 77.04 to 1036.47 ± 79.81 when in group and to 784.71 ± 55.88 ng/ml when isolated), luteinizing hormone (from 0.84 ± 0.09 to 0.58 ± 0.05 when in group and to 0.52 ± 0.06 ng/ml when isolated) and prolactin (from 5.18 ± 0.33 to 9.37 ± 0.96 when in group and to 10.18 ± 1.23 ng/ml when isolated) secretion, but not in terms of follicle-stimulating hormone or testosterone secretion. The most important feature observed was that in each cage there was one animal with higher ACTH levels than the other two; furthermore, the exploratory behavior of this animal was different, indicating the occurrence of almost constant higher vigilance in this animal (latency to leave the den in group: 99.17 ± 34.95 and isolated: 675.3 ± 145.3 s). The data indicate that in each group there is an animal in a peculiar situation and its behavior can be detected by ACTH determination in addition to behavioral performance.

Changes of ongoing activity in Cebus monkey perirhinal cortex correlate with behavioral performance

A Cebus apella monkey weighing 4 kg was trained in a saccadic eye movement task and while the animal performed the task we recorded the extracellular activity of perirhinal cortical neurons. Although the task was very simple and maintained at a constant level of difficulty, we observed considerable changes in the performance of the monkey within each experimental session. The behavioral states responsible for such variation may be related to arousal, motivation or attention of the animal while engaged in the task. In approximately 20% (16/82) of the units recorded, long-term direct or inverse correlations could be demonstrated between the monkey's behavioral state and the cells' ongoing activity (independent of the visual stimulation or of the specific behavior along a trial). The perirhinal cortex and other medial temporal structures have long been associated with normal memory function. The data presented here were interpreted in terms of recent reports focusing on the subcortical afferents to temporal lobe structures and their possible role in controlling arousal, motivation, or attention.

Behavioral and physiological methods for early quantitative assessment of spinal cord injury and prognosis in rats

Methods for reliable evaluation of spinal cord (SC) injury in rats at short periods (2 and 24 h) after lesion were tested to characterize the mechanisms implicated in primary SC damage. We measured the physiological changes occurring after several procedures for producing SC injury, with particular emphasis on sensorimotor functions. Segmental and suprasegmental reflexes were tested in 39 male Wistar rats weighing 250-300 g divided into three control groups that were subjected to a) anesthesia, b) dissection of soft prevertebral tissue, and c) laminectomy of the vertebral segments between T10 and L1. In the lesion group the SC was completely transected, hemisected or subjected to vertebral compression. All animals were evaluated 2 and 24 h after the experimental procedure by the hind limb motility index, Bohlman motor score, open-field, hot-plate, tail flick, and paw compression tests. The locomotion scale proved to be less sensitive than the sensorimotor tests. A reduction in exploratory movements was detected in the animals 24 h after the procedures. The hot-plate was the most sensitive test for detecting sensorimotor deficiencies following light, moderate or severe SC injury. The most sensitive and simplest test of reflex function was the hot-plate. The hemisection model promoted reproducible moderate SC injury which allowed us to quantify the resulting behavior and analyze the evolution of the lesion and its consequences during the first 24 h after injury. We conclude that hemisection permitted the quantitation of behavioral responses for evaluation of the development of deficits after lesions. Hind limb evaluation scores and spontaneous exploration events provided a sensitive index of immediate injury effects after SC lesion at 2 and 24 h. Taken together, locomotion scales, open-field, and hot-plate tests represent reproducible, quantitatively sensitive methods for detecting functional deficiencies within short periods of time, indicating their potential for the study of cellular mechanisms of primary injury and repair after traumatic SC injury.

Behavioral changes induced by cocaine in mice are modified by a hyperlipidic diet or recombinant leptin

The objective of the present study was to determine if the acute behavioral effects of cocaine acutely administered intraperitoneally (ip) at doses of 5, 10 and 20 mg/kg on white male CF1 mice, 90 days of age, would be influenced by leptin acutely administered ip (at doses of 5, 10 and 20 µg/kg) or by endogenous leptin production enhanced by a high-fat diet. The acute behavioral effects of cocaine were evaluated in open-field, elevated plus-maze and forced swimming tests. Results were compared between a group of 80 mice consuming a balanced diet and a high-fat diet, and a group of 80 mice fed a commercially available rodent chow formula (Ralston Purina) but receiving recombinant leptin (rLeptin) or saline ip. Both the high-fat-fed and rLeptin-treated mice showed decreased locomotion in the open-field test, spent more time in the open arms of the elevated plus-maze and showed less immobility time in the forced swimming test (F(1,68) = 7.834, P = 0.007). There was an interaction between diets and cocaine/saline treatments in locomotion (F(3,34) = 3.751, P = 0.020) and exploration (F(3,34) = 3.581, P = 0.024). These results suggest that anxiolytic effects and increased general activity were induced by leptin in cocaine-treated mice and that low leptin levels are associated with behavioral depression. Chronic changes in diet composition producing high leptin levels or rLeptin treatment may result in an altered response to cocaine in ethologic tests that measure degrees of anxiety and depression, which could be attributed to an antagonistic effect of leptin.

Estrogens and male reproduction: a new concept

The mammalian testis serves two main functions: production of spermatozoa and synthesis of steroids; among them estrogens are the end products obtained from the irreversible transformation of androgens by a microsomal enzymatic complex named aromatase. The aromatase is encoded by a single gene (cyp19) in humans which contains 18 exons, 9 of them being translated. In rats, the aromatase activity is mainly located in Sertoli cells of immature rats and then in Leydig cells of adult rats. We have demonstrated that germ cells represent an important source of estrogens: the amount of P450arom transcript is 3-fold higher in pachytene spermatocytes compared to gonocytes or round spermatids; conversely, aromatase activity is more intense in haploid cells. Male germ cells of mice, bank voles, bears, and monkeys express aromatase. In humans, we have shown the presence of a biologically active aromatase and of estrogen receptors (alpha and ß) in ejaculated spermatozoa and in immature germ cells in addition to Leydig cells. Moreover, we have demonstrated that the amount of P450arom transcripts is 30% lower in immotile than in motile spermatozoa. Alterations of spermatogenesis in terms of number and motility of spermatozoa have been described in men genetically deficient in aromatase. These last observations, together with our data showing a significant decrease of aromatase in immotile spermatozoa, suggest that aromatase could be involved in the acquisition of sperm motility. Thus, taking into account the widespread localization of aromatase and estrogen receptors in testicular cells, it is obvious that, besides gonadotrophins and androgens, estrogens produced locally should be considered to be physiologically relevant hormones involved in the regulation of spermatogenesis and spermiogenesis.