Effect of long-term pinealectomy on serum LH levels and on cerebral serotonin metabolism in adult male rats

Two months after pinealectomy carried out in adult male rats previously exposed to a long photoperiod (L:D 14:10) during 10 weeks, the weight of seminal vesicles significantly increased in comparison with Sham-operated animals. Nevertheless, the weights of testes and ventral prostate did not change significantly. The serum LH concentration increased significantly by pinealectomy. The levels of serotonin and 5-hydroxiindolacetic acid significantly decreased in the hypothalamus and midbrain after pinealectomy.     

Changes in the cerebral serotonin and noradrenaline levels in the brains of white rats trained with emotionally different reinforcement]

The changes in the serotonin (5-OT) and noradrenaline (NA) content in the brain of rats taught on the emotionally-positive (food) and emotionally-negative (pain) reinforcement were compared. The process of animal learning was accompanied by increase in the biogenic amine level. But when the teaching was conducted on the emotionally-positive reinforcement there was a greater increase in the 5-OT and NA level than in the case of the emotionally negative reinforcement. The process of animal teaching on food reinforcement was accompanied by an elevation of 5-OT chiefly in the cerebral cortex which apparently reflected the active functioning of the 5-OT system. An intensification of the NA system occurred in teaching the animals in the defence situation. A conclusion was thus drawn that the character of the changes in the biogenic amine level in the brain during learning depended on the emotions experienced by the animal (the emotional reinforcement utilized).     

Effect of chronic D-fenfluramine administration on rat hypothalamic serotonin levels and release

D-fenfluramine, an anorectic agent in rats and man, was administered daily at doses 1.25, 2.5, 5 or 10 mg/kg/day for 10 days, and sacrificed 6 days later. Hypothalamic serotonin (5-HT) levels were unchanged in rats receiving 1.25-5 mg/kg/day of d-fenfluramine but reduced by 22% (p less than 0.01) at the highest drug dose (10 mg/kg/day); hypothalamic 5-hydroxyindole acetic acid (5-HIAA) levels were reduced by 15% (p less than 0.05) or 28% (p less than 0.01) in rats receiving 5 or 10 mg/kg/day of the drug, respectively. Hypothalamic slices prepared from rats which were previously treated with any of the drug doses spontaneously released endogenous 5-HT at rates that did not differ from those of vehicle-treated rats. 5-HT released with electrical field-stimulation was unaffected by prior d-fenfluramine treatment at doses of 1.25-5 mg/kg/day, and was reduced by 20% (p less than 0.05) from slices prepared from rats which received 10 mg/kg/day. 5-HIAA efflux was also attenuated by the highest drug dose. These data indicate that chronic administration to rats of customary anorectic doses of d-fenfluramine (i.e. 0.06-1.25 mg/kg) fail to cause long-lasting reductions in brain 5-HT release.     

Effect of acute and chronic administration of L- thyroxine and methimazole on blood levels of tryptophane, serotonin and 5-hydroxyindoleacetic acid in plasma of rats]

The effects of hyperthyreosis induced by the administration of thyroxine and hypothyreosis induced by the administration of methimazole on the levels of tryptophane, serotonin and 5-hydroxyindoleacetic acid in low-platelet blood plasma have been studied in Wistar rats. Thyroxine administration (120 micrograms/kg/24 h, intraperitoneally) lasting 7 days caused a decrease in serotonin concentration by 38 per cent. The level of this amine in rats receiving thyroxine during three months was elevated by almost three times. Tryptophane concentration did not change following thyroxine administration. Methimazole administration lasting 14 days (oral dose 15 mg/kg/24 h) caused an increase in tryptophane concentration by 34 per cent and in serotonin concentration by 24 per cent. Long-term hypothyreosis induced by methimazole administration lasting three months caused an 39 per cent increase in tryptophane and 38 per cent increase in serotonin concentration. Neither hyperthyreosis induced by thyroxine administration nor hypothyreosis induced by methimazole++ caused any changes in the concentration of 5-hydroxyindoleacetic acid. The importance of serotonin in pathogenesis of clinical symptoms accompanying the states of deficit or excess of thyroid hormones needs further elucidation.     

Platelet serotonin levels and gonadal hormones in rats

The role of gonadal hormones in the control of platelet serotonin levels was studied by evaluating the effect of sexual maturation in rats of both sexes and the time-course of changes following gonadectomy performed either prepubertally or on sexually mature animals. In males, platelet serotonin levels remained fairly stable during sexual maturation as well as during the whole postgonadectomy period monitored (four months). In females, somewhat higher values of platelet serotonin levels in adult than in sexually immature animals were found (9%, p less than 0.001, N = 34). A slight decrease of platelet serotonin (10-18%, p less than 0.05) was observed following ovariectomy of sexually mature females, but it was of transient nature. When females were ovariectomized prepubertally a tendency towards permanently lower platelet serotonin levels was noticed. These results suggest that gonadal hormones have no major role in the control of platelet serotonin levels in rats, although a subtle hormonal modulation of this platelet variable in females may exist.     

Effect of mescaline on cerebral cholinesterases and on exploratory behavior in rats]

In this study the Authors had the purpose to evaluate the action of a psychotomimetic substance (mescaline) on behavior (exploring behaviour and spontaneous motility) and on cerebral biochemistry (cholinesterase activity) of rat. The mescaline has shown to be active both on behaviour (increasing the spontaneous motility) and on biochemistry (decreasing the total cholinesterase activity). From the examination of the results of this work it could be cautiously assumed the hypothesis that the behavioural effects of mescaline are related (at least partially) to modifications of the cholinergic system at the cerebral level.     

Effect of brain serotonin on the arterial pressure and plasma renin in normal and hypertensive rats]

The effects of changes in brain serotonin content after injections of p-chlorophenylalanine (p-CPA), L-5-hydroxytryptophan (L-5HTP) and 5-6-dihydroxytryptamine (5-6DHT) on the mean arterial pressure (MAP), plasma renin activity (PRA) and peripheral levels of atrial natriuretic peptide (ANP) have been studied in normal and hypertensive (2K:1C model) male Wistar rats. The p-CPA (250 mg/kg) and L-5HTP (200 mg/kg) were injected i.p., while 5-6 DHT (15 micrograms/animal in 10 mu/animal vehicle) was injected into lateral brain ventricles. The effects were studied 24 h after the p-CPA injection, 2 h after L-5HTP and 10 or 20 days after 5-6DHT administration. The fall in brain serotonin produced by p-CPA and 5-6DHT did not modify the MAP values in the normal and hypertensive rat model, whereas the increase induced after L-5HTP injection only caused a slight decrease in arterial pressure in normotensive animals. The ARP experimented remarkable rises in the normal and hypertensive rats, these values increasing after L-5HTP and falling after p-CPA and 5-6 DHT injections. Similar changes are detected in the normal group after administration of these substances related to serotoninergic brain activity. The ANP levels rose after renal artery constriction, and they are not affected by the above mentioned substances. Only p-CPA and 5-6DHT reduced a low decrease in the ANP levels 10 days after their administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of exogenous serotonin on intragastric pH and its influence on serum gastrin levels in rats.

The effect of various doses of serotonin on the serum gastrin levels and intragastric pH in rats, was studied. After serotonin administration of 10 mg/kg i.p., a significant increase in serum gastrin levels was noted, as well as a strong increase in the intragastric pH. It was also observed that a lower dose, 5 mg/kg i.p., significantly increased serum gastrin levels, while intragastric pH was not affected, remaining at baseline values throughout the study. These results suggest that the increase observed in serum gastrin levels after administration of exogenous serotonin is not mediated by increase in intragastric pH.     

Effect of negative air ions upon emotionality and brain serotonin levels in isolated rats

The effect of small negative air ions on the emotional behavior and brain serotonin content of isolated rats was studied. The results indicate that isolated subjects were more reactive to handling and had larger levels of serotonin than did isolated subjects undergoing continuous ion treatment. Group housed subjects were less reactive to handling than were either isolated subjects or isolated subjects intermittently exposed to ions. Thus ions were effective in reducing both emotionality and serotonin. Only continuous ion treatment was effective.

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Zusammenfassung Die Wirkung kleiner negativer Luftionen auf das Verhalten und den Serotoningehalt des Gehirns wurde an isolierten Ratten untersucht. Isolierte Tiere reagierten im Verhalten auf Ergreifen mit der Hand stärker und der Serotoningehalt war höher als bei gleich isolierten Tieren, die zusätzlich intermittierend Luftionen ausgesetzt waren. Durch Luftionen konnte danach die Emotionalität und der Serotoninspiegel herabgesetzt werden.

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Resume On étudie ici les répercussions de petits ions négatifs de l'air sur le comportement et le taux de sérotonine du cerveau de rats isolés. Les bêtes isolées réagissent plus violemment lorsqu'on les saisit à la main et leur taux de sérotonine est plus élevé que chez des bêtes, isolées également, mais auxquelles on a donné à respirer par intermittence des ions négatifs. Par conséquent, l'adjonction d'ions à l'air respiré a permis d'abaisser aussi bien l'impressionnabilité que le taux de sérotonine.

     

Effect of scopolamine on formation and fixation of temporary connections in rats with altered brain serotonin levels

The influence of scopolamine on elaboration and maintenance of conditioned reflexes of two-way avoidance was studied in rats under conditions of excess and deficit of serotonin in the brain. Administration of scopolamine to intact rats accelerated conditioning and did not prevent fixation of the reflex. Administration of scopolamine to animals with a lowered level of serotonin in the brain (by means of para-chlorophenylalanine) impaired conditioning and induced amnesia. In animals with ablated raphe nuclei, the same dose of scopolamine did not prevent elaboration and maintenance of conditioned reflexes. Accumulation of scopolamine in the brain by means of 5-oxytryptophan abolished acceleration of conditioning, which is specific for scopolamine, and affected the preservation of the reflexes. Against the background of the action of iprozid, scopolamine impaired the conditioning and tended to deteriorate the maintenance of conditioned reflexes. It is assumed that the serotoninergic system exerts a modulating influence on the activity of the brain cholinergic and cholinoreactive mechanisms.     

Effect of repeated alcohol administration on urine secretion and antidiuretic hormone in rats]

The administration of ehtanol by gavage immediately produced a maintened hyperdiuresis, a transient decrease of urinary osmolality and antidiuretic hormone secretion, followed by increased plasmatic and urinary antidiuretic hormone concentrations. Chronic intoxication enhanced these effects probably due to central disturbance.