The impact of combined administration of paraquat and maneb on motor and non-motor functions in the rat.

Paraquat (PQ) and maneb (MB) are potential risk factors for Parkinson's disease. However, their impact on non-motor disorders, monoamine neurotransmission and basal ganglia function is not clearly determined. Here we investigated the effects of combined treatment with PQ/MB on motor behavior, anxiety and "depressive-like" disorders, tissue content of monoamines, and subthalamic nucleus (STN) neuronal activity. Male Sprague-Dawley rats were intoxicated by PQ (10 mg/kg) and MB (30 mg/kg) twice a week. Two weeks later, the majority of animals (group 1, 16/26) showed a severe loss of body weight with tremor and respiratory distress and others (group 2, 6/26) showed only tremor. Animals of group 2 received PQ/MB during four weeks before developing weight loss. A last group (group 3, 4/26) was insensitive to PQ/MB after 6 weeks of injections. Groups 1 and 2 displayed a failure of motor activity and motor coordination. Group 3 showed slight motor deficits only after the last injection of PQ/MB. Moreover, PQ/MB induced anxiety and "depressive-like" behaviors in animals of groups 2 and 3. Biochemical analysis showed that PQ/MB reduced striatal dopamine (DA) tissue content paralleled by changes in the activity of STN neurons without changing the content of norepinephrine and serotonin in the cortex. Our data provide evidence that individuals are not equally sensitive to PQ/MB and show that the motor deficits in vulnerable animals, are not only a result of DA neuron degeneration, but may also be a consequence of peripheral disabilities. Nevertheless, the parkinsonian-like non-motor impairments may be a direct consequence of the bilateral DA depletion.

Lead intoxication induces noradrenaline depletion, motor nonmotor disabilities, and changes in the firing pattern of subthalamic nucleus neurons.

Lead intoxication has been suggested as a high risk factor for the development of Parkinson disease. However, its impact on motor and nonmotor functions and the mechanism by which it can be involved in the disease are still unclear. In the present study, we studied the effects of lead intoxication on the following: (1) locomotor activity using an open field actimeter and motor coordination using the rotarod test, (2) anxiety behavior using the elevated plus maze, (3) "depression-like" behavior using sucrose preference test, and (4) subthalamic nucleus (STN) neuronal activity using extracellular single unit recordings. Male Sprague-Dawley rats were treated once a day with lead acetate or sodium acetate (20 mg/kg/d i.p.) during 3 weeks. The tissue content of monoamines was used to determine alteration of these systems at the end of experiments. Results show that lead significantly reduced exploratory activity, locomotor activity and the time spent on the rotarod bar. Furthermore, lead induced anxiety but not "depressive-like" behavior. The electrophysiological results show that lead altered the discharge pattern of STN neurons with an increase in the number of bursting and irregular cells without affecting the firing rate. Moreover, lead intoxication resulted in a decrease of tissue noradrenaline content without any change in the levels of dopamine and serotonin. Together, these results show for the first time that lead intoxication resulted in motor and nonmotor behavioral changes paralleled by noradrenaline depletion and changes in the firing activity of STN neurons, providing evidence consistent with the induction of atypical parkinsonian-like deficits.

Role of the pineal gland and melatonin in the photoperiodic control of hypothalamic gonadotropin-releasing hormone in the male jerboa (Jaculus orientalis), a desert rodent.

The neuroendocrine mechanism underlying seasonal changes in gonadal activity of the jerboa, a desert hibernating rodent adapted to harsh climatic conditions, are poorly understood. We investigated the role of the pineal gland and melatonin in the photoperiodic control of hypothalamic gonadotropin-releasing hormone (GnRH). Intact and pinealectomized male jerboas were subjected to short photoperiod, while others were kept under long photoperiod and injected daily with melatonin or vehicle. Testes activity was monitored by evaluating the testes volume during 10 weeks. GnRH immunoreactivity was investigated quantitatively with image analysis. Following melatonin administration, the hormone peaked in plasma after 30 min, with return to control levels 2.5 h later. Exposure to short photoperiod and melatonin resulted in marked increase in the number of GnRH-containing cells in the preoptic area and mediobasal hypothalamus, whereas GnRH immunoreactivity of fibers and terminals in the median eminence decreased under these conditions. The findings indicate that in the jerboa short photoperiod induces testicular regression by prolonging the duration of melatonin as an endocrine signal. This mechanism probably involves inhibition of GnRH release in the median eminence, with consequent accumulation of GnRH in perikarya of the preoptic area and mediobasal hypothalamus. Interestingly, GnRH cells of the median eminence did not appear to be influenced by the photoperiod and pineal melatonin, whereas their number was increased by exogenous melatonin. The latter data suggest for the first time the involvement of an extrapineal melatonin, whose origin remains to be identified, in the modulation of the GnRH regulatory system in rodents.

Daytime alertness, mood, psychomotor performances, and oral temperature during Ramadan intermittent fasting.

During the month of Ramadan, Moslems abstain from drinking and eating daily between sunrise and sunset. This change of meals schedule is accompanied with changes in sleep habit, which may affect diurnal alertness. This study examined the effect of Ramadan intermittent fasting on the diurnal alertness and oral temperature in 10 healthy young subjects. The cognitive task battery including movement reaction time (MRT), critical flicker fusion (CFF) and visual analogue scale, was administered at 6 different times of the day: 09.00, 11.00, 13.00, 16.00, 20.00 and 23.00 h on the 6th, 15th, and 28th days of Ramadan. The baseline day was scheduled one week before Ramadan, and the recovery day 18 days after this month. Oral temperature was measured prior to each test session and at 00.00 h. During Ramadan oral temperature decreased at 09.00, 11.00, 13.00, 16.00 and 20.00 h and increased at 23.00 and 00.00 h. Subjective alertness decreased at 09.00 and 16.00 h and increased at 23.00 h. Mood decreased at 16.00 h. MRT was increased at the beginning of Ramadan (R6) and CFF was not changed. These results showed that daytime oral temperature, subjective alertness and mood were decreased during Ramadan intermittent fasting.

Photic regulation of mt1 melatonin receptors in the Siberian hamster pars tuberalis and suprachiasmatic nuclei: involvement of the circadian clock and intergeniculate leaflet.

In the Siberian hamster suprachiasmatic nuclei and pars tuberalis of the pituitary, high affinity mt1 melatonin receptors are present. We have previously shown that night applied light pulse induced an increase in mt1 mRNA expression in the suprachiasmatic nuclei of this species, independently of the endogenous melatonin. Here, we report the photic regulation of melatonin receptor density and mRNA expression in the suprachiasmatic nuclei and pars tuberalis of pinealectomized Siberian hamsters and the implication in this control of either the circadian clock or the intergeniculate leaflet. The results show that: (1) A 1-h light pulse, delivered during the night, induces a transitory increase in mt1 mRNA expression in the suprachiasmatic nuclei and pars tuberalis. After 3 h this increase has totally disappeared (suprachiasmatic nuclei) or is greatly reduced (pars tuberalis). (2) The melatonin receptor density, in the suprachiasmatic nuclei, is not affected by 1 or 3 h of light, while it is strongly increased in the pars tuberalis. (3) In hamsters kept in constant darkness, the mt1 mRNA rise is gated to the subjective night in the suprachiasmatic nuclei and pars tuberalis. In contrast, the light-induced increase in melatonin binding is also observed in the subjective day in the pars tuberalis. (4) intergeniculate leaflet lesion totally inhibits the mt1 mRNA expression rise in the suprachiasmatic nuclei, while it has no effect on the light-induced increase in mt1 mRNA in the pars tuberalis. However, the light-induced increase in melatonin receptor density is totally prevented by the intergeniculate leaflet lesion in the pars tuberalis. These results show that: (1) the photic regulations of mt1 mRNA expression and receptor density are independent of each other in both the suprachiasmatic nuclei and pars tuberalis; and (2) the circadian clock and the intergeniculate leaflet are implicated in the photic regulation of melatonin receptors but their level of action differs totally between the suprachiasmatic nuclei and pars tuberalis.

Role of the thalamic intergeniculate leaflet and its 5-HT afferences in the chronobiological properties of 8-OH-DPAT and triazolam in syrian hamster.

The 5-HT(1A/7) receptor agonist 8-hydroxy-2-[di-n-propylamino]-tetralin (8-OH-DPAT) has chronobiological effects on the circadian system and, in the Syrian hamster, it is known that serotonergic (5-HT) projections connecting the median raphe nucleus to the suprachiasmatic nuclei (SCN) of the hypothalamus are a prerequisite for the expression of 8-OH-DPAT-induced phase advance of locomotor activity rhythm. We examined the possible involvement of the thalamic intergeniculate leaflet (IGL) in the phase-shifting properties of 8-OH-DPAT injections at CT7. Bilateral electrolytic lesions of the IGL blocked phase-shift responses to 8-OH-DPAT of the activity rhythm. Phase changes induced by injections of 8-OH-DPAT at CT7 and triazolam (Tz), a short-acting benzodiazepine, at CT6 were also studied after bilateral chemical lesion of the 5-HT fibres connecting the dorsal raphe nucleus (DR) to IGL. Destruction of 5-HT fibres within the IGL blocked the phase-shift response to Tz, but not the phase-shift response to 8-OH-DPAT. In conclusion, (a) IGL is essential for the phase-shifting effect of peripheral 8-OH-DPAT injections; (b) 5-HT fibres connecting DR to IGL are necessary for the expression of the phase-shifting effect of Tz but not of 8-OH-DPAT.

Ventromedial nuclei of the hypothalamus are involved in the phase advance of temperature and activity rhythms in food-restricted rats fed during daytime.

Daily rhythms are synchronized to the light-dark cycle (LD) via a circadian clock located in the suprachiasmatic nuclei. A timed caloric restriction phase advances daily rhythms of body temperature and wheel-running activity in rats kept under LD. Because lesions of the ventromedial hypothalamic nuclei (VMH) prevent the fasting-induced changes in the day-night pattern of activity, it was hypothesized that the VMH might participate in the caloric restriction-induced phase changes. To test this hypothesis, rats with electrolytic or ibotenic acid lesions of VMH and control rats were fed 2 h after lights on 50% of ad lib food intake. During the preceding fed state, rats with electrolytic lesions of VMH displayed a less marked day-night difference in locomotor activity and a phase-advanced acrophase of temperature rhythm (2 h) compared to those of sham-operated rats. These effects were not found in fed rats with ibotenic lesions of VMH, suggesting that these effects of electrolytic lesions were due to disruption of undetermined fibers of passage. In response to a timed caloric restriction, the nocturnal peak of temperature rhythm was phase advanced by 7 h in sham-operated rats. Their day-night pattern of activity was also phase advanced towards the time of feeding. In both groups of food-restricted VMH-lesioned rats, the acrophase of temperature rhythm plateaued 3 h later than in sham-operated group. The phase advance of body temperature was, therefore, reduced to 4 h by ibotenic lesions of VMH and to 2 h by electrolytic lesions. Except for a feeding-associated component of activity expressed in control and VMH-lesioned rats, no significant change in day-night pattern of activity was detected in VMH-lesioned rats, either by electrolytic or ibotenic lesions. These results indicate that neuronal damage of the VMH limits the phase-advancing properties of a timed caloric restriction on the daily rhythms of temperature and locomotor activity.

How do the suprachiasmatic nuclei of the hypothalamus integrate photoperiodic information?

The suprachiasmatic nucleus of the hypothalamus (SCN) plays an essential role in the generation and maintenance of circadian rhythms in mammals. The SCN activity is also dependent upon the photoperiod. The duration of the SCN sensitive phase to light, in term of Fos induction, is variable and tied to the length of the night. The question is how and by which pathways can photoperiod influence SCN? It is possible following the theoretical model of evening and morning component of the clock that the SCN build itself the photoperiodic signal. That the SCN integrate the photoperiodic information through indirect neural or neuroendocrine pathways is also to consider. Data in favor of these different interpretations are presented.

Vasopressin in the brain of a desert hibernator, the jerboa (Jaculus orientalis): presence of sexual dimorphism and seasonal variation.

The distribution of vasopressin innervation in the brain of the jerboa (Jaculus orientalis) was investigated, with special attention to sex differences and seasonal variations. Vasopressin perikarya were observed in the paraventricular and supraoptic nuclei, the suprachiasmatic nucleus, the periventricular nucleus, the medial preoptic area, the bed nucleus of the stria terminalis, and the medial amygdaloid nucleus. In addition, vasopressin cell bodies were observed in the ventral retrochiasmatic area. After treatment with colchicine, vasopressin perikarya were also observed around the organum vasculosum laminae terminalis, in the medial diagonal band of Broca, and in the dorsal medial preoptic nucleus. Vasopressin fibers were also found to be more widespread in the jerboa brain than in other rodents. Fibers were observed in the medial diagonal band of Broca, the stria medullaris, the tuber cinerum, the area postrema, the medial vestibular nucleus, and the dorsal motor nucleus of the vagus. Sexual dimorphism and seasonal variation in vasopressin immunoreactivity were observed in areas that not only showed a testosterone-dependent vasopressin innervation in other rodents but also in the paratenial and mediodorsal thalamic nuclei, the tuber cinerum, the supramammillary complex, the zona incerta, the interpeduncular complex, and the dorsal and medial raphe nuclei. A denser vasopressin innervation was observed in spring/summer (sexual active period) than in autumn. Numerous brain structures contained vasopressin receptors (cerebral cortex, hypothalamus, substantia nigra, dentate gyrus, thalamic nuclei, superior colliculus, dorsal cochlear nucleus, and cerebellum); no sex- or season-related differences were observed. These data indicate a high level of vasopressin in the jerboa brain, which may reflect an adaptation to its harsh bioclimatic environment.

Seasonal variation in NPY immunoreactivity in the suprachiasmatic nucleus of the jerboa (Jaculus orientalis), a desert hibernator.

Using immunocytochemical techniques the seasonal variation in NPY immunoreactive fibers was investigated in the suprachiasmatic nucleus of both male and female jerboas. During the period of sexual quiescence (autumn), the amount of NPY immunoreactive fibers in the suprachiasmatic nucleus of both male and female jerboas was higher than in the period of sexual activity (spring-middle of summer). Compared with the respective control groups, castration during the period of sexual activity and testosterone or estrogen supplementation in sexually inactive animals did not affect NPY immunolabeling. These results indicate that the seasonal variation observed in NPY immunoreactivity in the suprachiasmatic nucleus of the jerboa is independent of circulating levels of steroid hormones. The possible influence of another hormonal system or a direct influence of an external factor such as photoperiod on NPY content in the suprachiasmatic nucleus remains to be determined.

An attempt to correlate brain areas containing melatonin-binding sites with rhythmic functions: a study in five hibernator species.

High affinity melatonin-binding sites have been described, by means of autoradiography with 2-125I-melatonin as the ligand, in more than 60 brain areas of about 20 mammalian species, with dramatic variations in the nature and number of labelled structures among the different species studied. As melatonin is involved in the synchronization of biological rhythms, we have tried to correlate the brain areas containing melatonin-binding sites with some rhythmic functions typical of given species. Therefore, we have studied the location of melatonin-binding sites in the complete brain of five long-day breeders with hibernation cycles, viz. one insectivore and four rodents. With the exception of the suprachiasmatic nuclei and the pars tuberalis of the pituitary, both of which contain binding sites in all five species, few reactive structures are common, even among species from the same family, e.g. the edible dormouse and the garden dormouse.

Mapping of [3H]vasopressin binding sites in the brain of jerboa (Jaculus orientalis) by an high resolution beta-radio imager.

The distribution of vasopressin receptors in the brain of the jerboa (Jaculus orientalis) was studied using tritiated arginin vasopressin ([3H]vasopressin). beta-Particles emitted from tritiated ligand bound to brain sections were detected by a newly developed beta-radio imager to generate a light spot which was read by a charge coupled device camera. The number and coordinate of the center of gravity of the light spot were recorded. After summation in pixels of the counts collected during 2-20 h, an image was produced representing the distribution of [3H]vasopressin bound to brain sections. Specific vasopressin binding was detected in various brain regions such as the cerebral cortex, islands of Calleja, pallidum, amygdala and the hippocampus as well as in the pituitary gland. The intensity of the binding was quantified directly from the images obtained and expressed in decays/min/surface unit. The linearity of this method of detection allowed a relevant measurement of non-specific binding, therefore its subtraction from images representing the total binding. Three-dimensional reconstructions of labeled structures were also performed. The presence of numerous vasopressin receptors in the jerboa hippocampus suggests a major role for this neuropeptide in this part of the brain.

Sexual differences and seasonal variations in vasoactive intestinal peptide immunoreactivity in the suprachiasmatic nucleus of jerboa (Jaculus orientalis).

The sexual differences and the seasonal variation in the vasoactive intestinal peptide (VIP) content of the suprachiasmatic nucleus (SCN) of a desert rodent, the jerboa (Jaculus orientalis) were studied using immunocytochemical techniques. During the period of sexual activity (spring-early summer), the VIP immunoreactivity in the SCN was higher in females than in males. In the period of sexual quiescence (autumn), both males and females exhibited an even more intense VIP immunoreaction in the SCN as compared to spring. However, during this period, the sex-related differences in the VIP content of the SCN observed in spring were no longer detectable. The direct possible influence of sex hormones on the VIP content in the SCN, and the physiological significance of the seasonal variation observed in the VIP immunoreactivity in the SCN in this species remains to be determined.

Seasonal variations in pineal 5-methoxytryptophol (5-ML) concentrations and in the daily pattern of pineal 5-ML and melatonin in the desert rodent Jaculus orientalis: effect of prolonged illumination during the night.

Seasonal variations in daytime pineal 5-methoxytryptophol (5-ML) and in the daily pattern of both pineal 5-ML and melatonin concentrations were measured by radioimmunoassay in male and female jerboas, Jaculus orientalis. Pineal 5-ML content was found to be low in winter and spring and showed a short but marked increase in summer. A clear daily rhythm was present in pineal 5-ML in September, with high concentrations during daytime and low concentrations during nighttime. In May there was a considerable drop in the daytime values and a marked decrease in the amplitude of the rhythm, while in December the daily rhythm completely disappeared. On the contrary, a clear daily rhythm was observed for pineal melatonin in September, December, and May with high values during nighttime and low values during daytime; no differences in the amplitude of the rhythm could be observed. Illumination during early night prevented both the nocturnal decrease of 5-ML and the increase of melatonin in September; in May illumination had no clear effect on 5-ML, while it prevented the normal increase of melatonin. These results suggest a possible desynchronization between the regulation of 5-ML and melatonin synthesis and release, and stress the complexity of the mechanisms involved in the environmental synchronization of seasonal functions.

Alpha-adrenoceptors and monoamine contents in the cerebral cortex of the rodent Jaculus orientalis: effects of acute cold exposure.

The tritiated adrenergic antagonists prazosin ([3H]PRZ) and idazoxan ([3H]IDA, or RX-781094) bind specifically and with high affinity to alpha 1- and alpha 2-adrenoceptors respectively, and were used to measure adrenoceptors in membrane preparations obtained from the cerebral cortex of Jaculus orientalis. Membrane preparations were also obtained from a group of cold exposed animals, to determine whether these adrenoceptors could be modified by a thermic stress. The density of receptors (Bmax; maximum binding capacity) and the dissociation constant (Kd 25 degrees C) were estimated by iterative modelling, and by using the procedure of Hill. After acute cold exposure (16 hr, 5 degrees C) there was a decrease in the affinity of the alpha 1-adrenoceptors, as judged by the Kd 25 degrees C for [3H]PRZ, with no changes in the Bmax. The alpha 2-sites did not show any significant changes, as revealed by [3H]IDA binding. Pretreatment of the membrane preparations from control animals with the disulfide and sulfhydryl reactives DL-dithiothreitol, 5,5'-dithiobis-(2-nitrobenzoic acid) and N-ethylmaleimide decreased specific [3H]PRZ and [3H]IDA binding, with minor changes in non-specific counts, indicating that the fixation of these ligands was to the receptor proteins. The endogenous cortical monoamine contents were also determined in the frontal cerebral cortex of these same animals, using high performance liquid chromatography with electrochemical detection. The catecholamine levels and their major metabolites were found to be stable in the cortex after the acute thermic stress, but there was a marked reduction in serotonin with a normal content in 5-hydroxyindole-3-acetic acid.