RESUMEN
The effects of American ginseng (Panax quinquefolium) on male rat copulatory behavior were investigated. Adult Sprague-Dawley rats were administered either 10, 50 or 100 mg/kg of Panax quinquefolium or a sesame oil vehicle per os (p.o.) for 28 days and copulatory behavior parameters were measured. Ginseng-treated male rats demonstrated a significant decrease in mount, intromission and ejaculation latencies compared to vehicle controls. Hormone analyses revealed no difference in plasma luteinizing hormone or testosterone levels between ginseng- and vehicle-treated animals; however, plasma prolactin levels were significantly reduced by all doses of ginseng tested. When male rats were treated with the 100 mg/kg dose of ginseng for 1, 14 or 28 days, mount and intromission latencies were significantly reduced at 14 and 28 days of daily ginseng treatment, whereas ejaculation latency was significantly reduced after 1 day of ginseng treatment when compared to vehicle controls. Plasma prolactin levels were also significantly decreased after 14 and 28 days of daily ginseng administration. There were no differences in body weight or in testes, seminal vesicle, anterior pituitary or spleen weights between ginseng- and vehicle-treated rats. These results demonstrate that P. quinquefolium significantly facilitates male copulatory behavior. The reduction in plasma prolactin levels suggests that ginseng-induced alterations in dopaminergic neurotransmission may play a role in the ability of P. quinquefolium to stimulate copulatory behavior in the male rat.
Asunto(s)
Copulación/efectos de los fármacos , Panax , Plantas Medicinales , Animales , Relación Dosis-Respuesta a Droga , Femenino , Hormona Luteinizante/sangre , Masculino , Tamaño de los Órganos/fisiología , Prolactina/sangre , Ratas , Ratas Sprague-Dawley , Estimulación QuímicaRESUMEN
The paper describes an electronic device that improves the feedback lighting (LDFB) developed previously. LDFB links environmental lighting conditions to locomotor or other monitored behavior. Subjective Night Light (SNL) has the following advantages over LDFB: it eliminates the multiple transitions between light and dark; it allows for precise control over lighting so that a light signal of variable duration can be phase locked to any phase of the subjective night; it dissociates to a much greater extent any potential cognitive perception of the link between locomotor activity and lighting; and it can be programmed easily. Finally, SNL retains the significant advantage of LDFB in its ability to maintain phase relationship with the endogenous biologic rhythms even in circumstances of phase-shifting or free-running conditions. The SNL system is made from components that can be purchased at most electronics outlets for less than US$100.
Asunto(s)
Ritmo Circadiano/fisiología , Estimulación Luminosa/instrumentación , Psicología Experimental/instrumentación , Animales , Cricetinae , Electrónica , Masculino , Actividad Motora/fisiología , Programas InformáticosRESUMEN
BACKGROUND: Biological clocks time many physiological parameters with periodicities close to 24 h; those which persist in the absence of environmental cues are circadian. An earlier shuttle experiment (STS-9) examined circadian pacemaker function and growth rate of Neurospora crassa and demonstrated damped rhythm amplitudes, increased variability in period lengths and altered growth rates. HYPOTHESIS: Postflight studies suggested that accelerative forces of launch could have induced rhythm alterations. Differences in growth rate may have been due to an alteration of metabolic rate. METHODS: Race tubes inoculated with bd or csp strains were flown aboard STS-32, exposed to ambient mid-deck temperatures throughout flight, and exposed to light only during marking procedures. Period, rhythm amplitude, and growth rate were determined and compared to orbital environmental controls (OES) and 25 degrees C ground controls (GC). RESULTS: Unlike the previous flight exposurement, the rhythm persisted quite normally. bd flight and OES cultures each displayed lengthened periods of a similar magnitude when compared to GC. The lengthened periods of csp flight cultures while longer than GC, were shorter than OES. Shuttle temperatures were relatively warm, however the increased period length in space was greater than predicted by the known Q10. Growth rates also increased substantially during flight, which could not be accounted for by thermal mechanisms alone. CONCLUSION: It is likely that some of the cultures may have entrained to the unexpected diurnal temperature variations; however, other cultures did not entrain, yet retained rhythmicity with increased periods. The results also suggest an increased metabolic rate during spaceflight.
Asunto(s)
Ritmo Circadiano , Neurospora crassa/crecimiento & desarrollo , Vuelo EspacialRESUMEN
This study examines the activity, axillary temperature (T(ax)), and ankle skin temperature (Tsk) of two male Rhesus monkeys exposed to microgravity in space. The animals were flown on a Soviet biosatellite mission (COSMOS 1514). Measurements on the flight animals, as well as synchronous flight controls, were performed in the Soviet Union. Additional control studies were performed in the United States to examine the possible role of metabolic heat production in the T(ax) response observed during the spaceflight. All monkeys were exposed to a 24-h light-dark cycle (LD 16:8) throughout these studies. During weightlessness, T(ax) in both flight animals was lower than on earth. The largest difference (0.75 degree C) occurred during the night. There was a reduction in mean heart rate and Tsk during flight. This suggests a reduction in both heat loss and metabolic rate during spaceflight. Although the circadian rhythms in all variables were present during flight, some differences were noted. For example, the amplitude of the rhythms in Tsk and activity were attenuated. Furthermore, the T(ax) and activity rhythms did not have precise 24.0 hour periods and may have been externally desynchronized from the 24-h LD cycle. These data suggest a weakening of the coupling between the internal circadian pacemaker and the external LD synchronizer.
Asunto(s)
Regulación de la Temperatura Corporal , Ritmo Circadiano , Vuelo Espacial , Ingravidez , Animales , Macaca mulatta , Masculino , Actividad MotoraRESUMEN
Experiments examining the photoperiodic effects of various light-dark cycles unexpectedly demonstrated that light during the subjective night is not necessarily photoinductive to the reproductive system of long day breeders. Feedback lighting (illumination in response to locomotor activity) and a high-frequency light-dark cycle with 1 minute (m) of light followed with 1 minute of dark (LD1m:1m) failed to maintain reproductive function in Syrian hamsters despite exposing the animal to 5-6 hours of light per cycle during the subjective night. In an effort to determine why feedback lighting and LD1m:1m do not maintain reproductive function, male Syrian hamsters were exposed to one of the following lighting conditions for ten weeks: a light-dark cycle with 14 hours of light followed by a 10 hour light-dark cycle of 1 minute of light followed by 1 minute of dark ¿LD14:10(1m:1m)¿; a cycle of a 14 hour light-dark cycle of 1 minute of light followed by 1 minute of dark, followed by 10 hours of dark ¿LD14(1m:1m):10)¿; a light-dark cycle of 2 hours of light and 21 hours of dark (LD2:21); a light-dark cycle of 2 hours of light and 22 hours of dark (LD2:22); LD2:21 in conjunction with feedback lighting (LD2:21/FB); LD2:22 in conjunction with feedback lighting (LD2:22/FB); constant dark (DD) or constant light (LL). All hamsters exposed to LD14(1m:1m):10 entrained. Only 7 of 12 hamsters exposed to LD14:10(1m:1m) entrained. This supports previous findings, which suggest that the circadian system has difficulty differentiating between LD1m:1m and LL. Exposure to LD2:22 and DD induced testicular regression, while LL, LD2:21 and LD14(1m:1m):10 maintained reproductive function, as expected. The addition of approximately 5 hours of nocturnal illumination by feedback lighting, however, not only failed to prevent reproductive regression in LD2:22, but attenuated the stimulatory nature of LD2:21. This suggests that feedback lighting is not only not stimulatory, but may be actively inhibitory. Perhaps this is due to a photoinhibitory effect of multitransitional nocturnal illumination. This hypothesis is supported by the finding that LD14:10(1m:1m) allows regression, while LD14(1m:1m):10 is stimulatory. These findings also imply that the state of the circadian system is instrumental in the reproductive system's interpretation of a light signal.
Asunto(s)
Ritmo Circadiano/fisiología , Luz , Fotoperiodo , Reproducción/fisiología , Ciclos de Actividad/efectos de la radiación , Animales , Ritmo Circadiano/efectos de la radiación , Cricetinae , Genitales Masculinos/anatomía & histología , Genitales Masculinos/efectos de la radiación , Masculino , Mesocricetus , Actividad Motora/efectos de la radiación , Tamaño de los Órganos , Estimulación Luminosa , Prolactina/sangre , Reproducción/efectos de la radiación , Testosterona/sangreRESUMEN
Circadian rhythms of wheel running and feeding were measured in the short-tailed shrew. Shrews were strongly nocturnal, and their activity rhythms entrained to both long-day (LD 16:8) and short-day (LD 6:18) photocycles. Under conditions of continuous light (LL) or darkness (DD), the activity rhythms free-ran with average periodicities of 25.1 hours and 24.1 hours, respectively. In LL the level of activity was depressed, and in some cases wheel running was completely inhibited. No significant sex differences were observed in the period or amplitude of the monitored circadian rhythms. All shrews fed throughout the day and night; however, unlike in previous reports, ultradian periods of feeding behavior were not found. The results are related to Aschoff's four observations for the effect of light on activity rhythms in nocturnal rodents.
Asunto(s)
Nivel de Alerta , Ritmo Circadiano , Luz , Actividad Motora , Musarañas , Animales , Conducta Alimentaria , Estaciones del Año , Musarañas/psicologíaRESUMEN
In an effort to determine the driving force of the diurnal variation of serotonin (5-HT) in the brain, over 500 Syrian hamsters were exposed to long photoperiods (LD17:7; LD), short photoperiods (LD8:16; SD), constant dark (DD) or constant light (LL) for 12 weeks. Hamsters exposed to LD or SD were sacrificed at 3 h intervals; those in constant conditions were sacrificed around the clock. The circadian time (CT) of tissue collection, in the animals in constant conditions, was determined from the onset of locomotor activity (defined as CT12; the beginning of the subjective night). Serotonin content was determined by HPLC with electrochemical detection in the medial basal hypothalamus (MBH); anterior hypothalamus (AH) and olfactory bulbs (OB). In LD and SD, 5-HT levels displayed significant diurnal variation in the MBH, AH and OB (ANOVA; P less than 0.001). The sine waves of the 5-HT rhythm in these conditions were similar in amplitude and phase with relation to lights on (i.e. high 5-HT content during the day and low content at night, with a sharp rise occurring just after lights on). This variation, however, was not apparent in animals exposed to DD or LL; 5-HT content did not display a significant diurnal oscillation. Since 5-HT failed to oscillate in the absence of environmental time cues, the rhythm is likely driven by the environment and not an internal circadian clock.
Asunto(s)
Ritmo Circadiano , Cricetinae/fisiología , Hipotálamo/fisiología , Iluminación , Mesocricetus/fisiología , Bulbo Olfatorio/fisiología , Serotonina/metabolismo , Animales , Hipotálamo/metabolismo , Mesocricetus/metabolismo , Bulbo Olfatorio/metabolismoRESUMEN
In an effort to determine the inductive component(s) of photic input in long day seasonal breeders, adult male Syrian hamsters (Mesocricetus auratus) were exposed to one of nine lighting conditions for a duration of 10 weeks: a light-dark cycle of 14 hours of light followed by 10 hours of dark (LD 14:10, a long photoperiod); LD 10:14 (a short photoperiod); a high frequency light-dark cycle of 1 hour of light and 1 hour of dark (LD 1:1); a higher frequency light-dark cycle of 1 minute of light and 1 minute of dark (LD 1m:1m); constant light (LL); constant dark (DD); feedback lighting (LDFB; a condition that illuminates the cage in response to locomotor activity); a feedback lighting neighbor control (LDFB NC; the animal receives the same light pattern as a paired animal in LDFB, but has no control over it); or reverse feedback lighting (rLDFB; a condition that darkens an illuminated cage in response to locomotor activity). Exposure to LL, LD 1:1, LD 1m:1m, LDFB and rLDFB significantly and similarly lengthened the free-running period of the locomotor rhythm when compared to the period of animals in DD. The paired tests and accessory reproductive glands weights, spermiogenesis, seminiferous tubule diameter and serum concentrations of testosterone, prolactin, LH and FSH, suggest that LD 14:10, LL, LD 1:1, rLDFB and LDFB NC maintain reproductive function in the Syrian hamster, while LD 10:14, DD, LD 1m:1m and LDFB do not. It is known that as little as two 1-second pulses of light are stimulatory if coincident with the subjective night (17.22). Thus, it is not surprising that LD 1:1 is stimulatory. LD 1m:1m is not stimulatory, however, despite an identical quanta of light per 24 hours and similar phase relationship. It appears that mere light exposure during the subjective night is not necessarily reproductively inductive. It would also appear that behaviorally generated light-dark cycles can be (i.e., LDFB), but are not necessarily (i.e., rLDFB) inhibitory to the maintenance of the reproductive system in long day breeders. Furthermore, the lighting pattern derived from LDFB is stimulatory if given exogenously (i.e., LDFB NC). Although it is not understood why light exposure that is coincident with the subjective night (i.e., LD 1m:1m and LDFB) is not stimulatory in long day breeders, a possible hypothesis is that an internal coincidence model is involved in the photoperiodic response and that multiple transitions during the subjective night may cause a dissociation of internal oscillations which must be in phase for light to be stimulatory.
Asunto(s)
Ritmo Circadiano/efectos de la radiación , Luz , Actividad Motora/efectos de la radiación , Periodicidad , Reproducción/efectos de la radiación , Animales , Cricetinae , Retroalimentación , Hormona Folículo Estimulante/sangre , Hormona Luteinizante/sangre , Masculino , Mesocricetus , Tamaño de los Órganos/efectos de la radiación , Prolactina/sangre , Espermatogénesis/efectos de la radiación , Testículo/anatomía & histología , Testosterona/sangreRESUMEN
Mature male Djungarian hamsters (Phodopus sungorus) were placed in individual light-tight, sound attenuated chambers and exposed to one of four lighting conditions for a duration of approximately seven weeks. The four lighting conditions were: constant light (LL); constant dark (DD); feedback lighting (LDFB; a condition that illuminates the cage in response to locomotor activity); or a feedback lighting neighbor control (LDFB NC; the animal receives the same light pattern as a paired animal in feedback lighting, but has no control over it). Exposure of hamsters to LL or LDFB produced significantly and similarly longer free-running periods of the locomotor activity rhythm than exposure of animals to DD. Hamsters exposed to LDFB NC did not free-run or entrain, but rather displayed "relative coordination". The paired testes and sex accessory glands weights suggest that in the Djungarian hamster, LL and LDFB exposed animals maintained reproductive function, whereas DD exposed animals did not. Animals exposed to LDFB NC had intermediate paired testes weights. Since several previous studies have demonstrated that short pulses of light, which are coincident with the subjective night, are photostimulatory, it is not surprising that LDFB maintained reproductive function in the mature Djungarian hamster. Feedback lighting, however, has been shown to be an insufficient stimulus to maintain reproductive function of mature male and female Syrian hamsters, and to the reproductive maturation of immature Djungarian hamsters. The results suggest that there may be slight, but significant differences in the way these two species interpret photoperiod, as well as a developmental change in the photoperiodic response of Djungarian hamsters.
Asunto(s)
Ritmo Circadiano/fisiología , Actividad Motora/fisiología , Fotoperiodo , Reproducción/fisiología , Ciclos de Actividad/efectos de la radiación , Glándulas Suprarrenales/anatomía & histología , Glándulas Suprarrenales/efectos de la radiación , Factores de Edad , Animales , Peso Corporal , Ritmo Circadiano/efectos de la radiación , Cricetinae , Genitales Masculinos/anatomía & histología , Genitales Masculinos/efectos de la radiación , Luz , Masculino , Actividad Motora/efectos de la radiación , Tamaño de los Órganos , Phodopus , Pigmentación/efectos de la radiación , Reproducción/efectos de la radiaciónRESUMEN
The circadian rhythm of conidiation in Neurospora crassa is thought to be an endogenously derived circadian oscillation; however, several investigators have suggested that circadian rhythms may, instead, be driven by some geophysical time cue(s). An experiment was conducted on space shuttle flight STS-9 in order to test this hypothesis; during the first 7-8 cycles in space, there were several minor alterations observed in the conidiation rhythm, including an increase in the period of the oscillation, an increase in the variability of the growth rate and a diminished rhythm amplitude, which eventually damped out in 25% of the flight tubes. On day seven of flight, the tubes were exposed to light while their growth fronts were marked. Some aspect of the marking process reinstated a robust rhythm in all the tubes which continued throughout the remainder of the flight. These results from the last 86 hours of flight demonstrated that the rhythm can persist in space. Since the aberrant rhythmicity occurred prior to the marking procedure, but not after, it was hypothesized that the damping on STS-9 may have resulted from the hypergravity pulse of launch. To test this hypothesis, we conducted investigations into the effects of altered gravitational forces on conidiation. Exposure to hypergravity (via centrifugation), simulated microgravity (via the use of a clinostat) and altered orientations (via alterations in the vector of a 1 g force) were used to examine the effects of gravity upon the circadian rhythm of conidiation.
Asunto(s)
Relojes Biológicos/fisiología , Ritmo Circadiano/fisiología , Neurospora crassa/fisiología , Vuelo Espacial , Ingravidez , Relojes Biológicos/efectos de la radiación , Centrifugación , Ritmo Circadiano/efectos de la radiación , Gravitación , Hipergravedad/efectos adversos , Luz , Neurospora crassa/genética , Neurospora crassa/crecimiento & desarrollo , Rotación , Factores de Tiempo , Simulación de IngravidezRESUMEN
The non-parametric model of entrainment suggests that brief pulses of light, delivered between dusk and dawn can simulate the phasing effects of full photoperiods or even constant light (LL). Feedback lighting (LDFB) is a lighting condition where individual animals, otherwise in constant darkness (DD), are exposed to light in response to a monitored behavior. The specific purpose of this type of illumination is to expose the circadian cycle to light only during the subjective night. LDFB has been used to support this hypothesis in several species of nocturnal rodents and one species of diurnal primate by producing similar free-running periods in LDFB as in LL. This lighting condition has also been used to test the hypothesis that exposing the subjective night to even short duration light pulses will maintain reproductive function in long day breeders. In the Syrian hamster (Mesocricetus auratus), however, LDFB is not as photostimulatory as LL despite extensive light exposure during the subjective night. In the experiments presented here, a group of immature male Djungarian hamsters (Phodopus sungorus) were placed in individual light-tight sound attenuated chambers where they had free access to food, water and an activity wheel. The animals were exposed to one of four lighting conditions [DD, LL, LDFB or a neighbor control of feedback lighting (LDFB NC)] for approximately 30 days shortly after weaning. LDFB NC is a lighting condition where a neighbor control hamster receives the identical lighting regime as a paired animal exposing itself to LDFB, yet the neighbor has no control over it. A fifth group was exposed to a light-dark cycle of 16 hours of light and 8 hours of dark (LD16:8). This group was housed in cages in a colony room and did not have access to a running wheel. The free-running periods of the locomotor activity rhythms for hamsters exposed to LDFB and LL were not similar, unlike the results for rats, Syrian hamsters, mice, monkeys and even mature Djungarian hamsters. Immature hamsters exposed to DD and LDFB NC developed more slowly than animals exposed to LL or LD16:8, while hamsters in LDFB developed at an intermediate rate. Thus, it appears that LDFB, although capable of inducing reproductive function in immature Djungarian hamsters, is not as photostimulatory as may have been expected from current photoperiodic models, despite substantial light exposure during the subjective night. Furthermore, this data may suggest that the circadian system of 18-48 day old Djungarian hamsters are still undergoing organizational maturation.
Asunto(s)
Ritmo Circadiano/fisiología , Luz , Actividad Motora/fisiología , Fotoperiodo , Maduración Sexual/fisiología , Glándulas Suprarrenales , Animales , Peso Corporal , Cricetinae , Retroalimentación , Color del Cabello , Masculino , Phodopus/fisiología , Vesículas SeminalesRESUMEN
Feedback lighting provides illumination primarily during the subjective night (i.e., the photosensitive portion of the circadian cycle) in response to a given behavior. This technique has previously been used to test the nonparametric model of entrainment in nocturnal rodents. In three species (Rattus norvegicus, Mesocricetus auratus, and Mus musculus), the free-running period of the locomotor activity rhythm was similar whether the animals were exposed to continuous light or discrete light pulses occurring essentially only during the subjective night (i.e., feedback lighting). In the current experiments, feedback lighting was presented to squirrel monkeys so that light fell predominantly during the subjective night. Feedback lighting was linked to the drinking behavior in this diurnal primate so that when the animal drank, the lights went out. Despite the seemingly adverse predicament, the monkeys maintained regular circadian drinking rhythms. Furthermore, just as the period of the free-running activity rhythms of nocturnal rodents exposed to continuous light or feedback lighting were similar, the period of the drinking rhythms of the squirrel monkeys in continuous light and feedback lighting were comparable (25.6 +/- 0.1 and 25.9 +/- 0.1 hours, respectively), despite a substantial decrease in the total amount of light exposure associated with feedback lighting. The free-running period of monkeys exposed to continuous dark (24.5 +/- 0.1 hours) was significantly shorter than either of the two lighting conditions (P < 0.001). The results presented for the drinking rhythm were confirmed by examination of the temperature and activity rhythms. Therefore, discrete light pulses given predominately during the subjective night are capable of simulating the effects of continuous light on the free-running period of the circadian rhythms of a diurnal primate. The response of squirrel monkeys to feedback lighting thus lends further support for the model and suggests that the major entrainment mechanisms are similar in nocturnal rodents and diurnal primates.
Asunto(s)
Ritmo Circadiano/efectos de la radiación , Conducta de Ingestión de Líquido/efectos de la radiación , Iluminación , Actividad Motora/efectos de la radiación , Animales , Temperatura Corporal , Oscuridad , Retroalimentación , Ratas , Saimiri , AguaRESUMEN
To further explore the validity of the non-parametric model of entrainment for predicting the phase-shifting effects of light pulses, we exposed rats to several intensities of continuous light (LL) and feedback lighting (LDFB). LDFB is a lighting condition that exposes the animal to light only during the interval of active locomotion; this interval is coincident with the photosensitive portion of the circadian cycle as defined by the phase-response-curve. This is achieved by linking lights on with locomotor activity. In addition to the comparison of LL with LDFB, the duration of the LDFB pulse was also varied in four rats. Whether rats were exposed to LL or LDFB, as light intensity increased, the free-running period (tau) of the locomotor activity rhythm also increased. This intensity-related increase in tau, which is known as the Aschoff effect, was similar for LL and LDFB 2 min at each light intensity (0.1, 1, and 100 lux). However, when the LDFB pulses were shortened from a duration of 2 min to a duration of approximately 1 sec, tau shortened significantly. These results demonstrate that the non-parametric model of entrainment adequately explains the major period-lengthening effects of LL. However, there are temporal limits to the light pulses that can be used to simulate the effects of LL (i.e., one second light pulses fail to produce the effects brought about by longer pulses).
Asunto(s)
Ciclos de Actividad , Ritmo Circadiano , Actividad Motora/fisiología , Animales , Retroalimentación , Femenino , Luz , Periodicidad , Estimulación Luminosa , RatasRESUMEN
Feedback lighting (LDFB), which illuminates an animal cage in response to active wheel running, exposes only the photosensitive portion of the phase-response curve to light. In the hamster, the photoinducible zone of the circadian rhythm of photoperiodic photosensitivity occurs during the interval of active wheel running. Since LDFB exposes the photoinducible zone almost as much as constant light (LL), we predicted that LDFB would maintain gonadal function just as LL does. Surprisingly, 10 male hamsters exposed to 1-sec pulses of LDFB for 8 wk had regressed testes similar to those of hamsters in continuous darkness (DD) and significantly smaller than hamsters exposed to LL (P less than 0.01). Two of 5 male hamsters exposed to 2-min pulses of LDFB underwent complete testicular regression and two had partially regressed testes. All females exposed to LDFB or to DD ceased showing cyclic signs of ovulation within 20 days, whereas most hamsters exposed to LL continued to show signs of cyclic ovulation. Six of the 8 hamsters exposed to LL had ova in their oviducts at autopsy, and also had significantly larger uteri (P less than 0.01) than hamsters exposed to DD or LDFB. None of the latter two groups (n = 6 and 9, respectively) had oviductal ova at autopsy. These results demonstrate that considerable exposure of the photoinducible zone to light does not necessarily maintain gonadal function. Light delivered to the photoinducible zone by LDFB may disrupt the normal alignment (internal coincidence) of circadian rhythms, thereby causing gonadal regression. Gonadal induction can occur when the photoinducible zone is exposed to light; however, it may not be the light itself, but rather the action of the light to alter the phase relationships of several oscillators, that causes induction and maintenance of the gonads.
Asunto(s)
Gónadas/fisiología , Luz , Actividad Motora , Animales , Ritmo Circadiano , Cricetinae , Femenino , Masculino , Mesocricetus/fisiología , Periodicidad , ReproducciónRESUMEN
This paper describes an electronic device through which environmental lighting conditions are linked to locomotor activity thus allowing only the photosensitive portions of a nocturnal rodents phase-response-curve to be exposed to light. In the past, this type of lighting schedule has been difficult, if not impossible, to present with an exogenously controlled lighting system due to the phase shifting ability of the rodent's circadian system. The feedback lighting system is made from components which can be purchased at most electronics outlets for less than $100.
Asunto(s)
Ritmo Circadiano , Etología/instrumentación , Luz , Actividad Motora/fisiología , Animales , Retroalimentación , Iluminación , Fisiología/instrumentación , RatasRESUMEN
Using feedback circuits, light exposure was linked to wheel-running activity in female albino rats. Because the photosensitive portions of the circadian cycle are known to coincide with wheel-running activity, the feedback circuits concentrated light on the photosensitive portions of the cycle. In this type of lighting, the free-running period of locomotor activity was directly proportional to the light intensity (i.e., the Aschoff effect), and at an intensity of 100 1x, cyclic ovulation caused. Both these effects, which were previously thought to result only from exposure to continuous light (LL), occurred even though these rats were exposed to only 4 h of light per circadian cycle. These results indicate that the consequences of LL are not due to the continuity of the light per se but represent the effects of light falling on discrete photosensitive portions of the circadian cycle.
Asunto(s)
Anovulación/fisiopatología , Estimulación Luminosa , Animales , Ritmo Circadiano , Femenino , Actividad Motora , Ratas , Ratas EndogámicasRESUMEN
A phase-response curve (PRC) for the circadian rhythm of locomotor activity was constructed for female Sprague-Dawley-derived rats kept in continuous darkness (DD) except when given a 1-h light pulse (150 lx) once each 2 wk. By use of the circadian onset of wheel running as the phase-reference point, the free-running period (tau) in DD was 24.09 h. Maximum phase delays and phase advances occurred in response to light pulses given during the first 5 and last 6 h of activity, respectively. The delay-to-advance ratio (D/A) of the PRC was 1.5. In a separate group of rats exposed to continuous light, tau increased by 1.45 h as illuminance was increased in log steps from 0.1 to 10 lx, thus demonstrating the Aschoff effect in rats. This increase in tau was large, considering the relatively low D/A of the PRC, suggesting that factors in addition to the D/A contribute to the Aschoff effect.