Search results for "serotonin"
showing 10 items of 414 documents
In vitro effects of putative neurotransmitters on synaptic ribbon numbers and N-acetyltransferase activity in the rat pineal gland
1992
The pineal contains a large number of classical transmitters and neuropeptides. Some of these neurochemicals are involved in the regulation of serotonin N-acetyltransferase (NAT) activity and hence in melatonin synthesis. Synaptic ribbons present in the pineal gland also exhibit a numerical day/night rhythm parallel to that of NAT activity. There is scarcity of information regarding the regulation of synaptic ribbon (SR) numbers. In the present study, we have investigated in vitro effects of a number of classical neurotransmitters and neuropeptides. NAT activity was used to monitor melatonin synthesis under the experimental conditions used. Norepinephrine (NE), Delta sleep-inducing peptide …
The effects of a number of short-term exogenous stimuli on pineal serotonin-N-acetyltransferase activity in rats
1984
The present study deals with the question as to what extent the sympathetically innervated rat pineal gland is affected by a number of short-term exogenous stimuli given during day-time, as assessed by measuring pineal serotonin-N-acetyltransferase activity (NAT) which is directly proportional to melatonin formation. In male Sprague-Dawley rats kept under LD 12:12 pineal NAT was statistically significantly depressed by physical immobilization for 2 hours, swimming for 15 min in water of 10 and 30 degrees C, exposure for 2 hours to cold (5 degrees C) or heat (40 degrees C), noise (90 db) for 2 hours and hunger for 17 hours. An increase in NAT was noted after swimming for 15 min in water of 2…
Lack of effect of oxytocin on the numbers of ?synaptic? ribbons, cyclic guanosine monophosphate and serotonin N-acetyltransferase activity in organ-c…
1993
In addition to the stimulating influence of the sympathetic system on the function of the mammalian pineal gland, neuropeptides such as neuropeptide Y, vasoactive intestinal polypeptide and arginine-vasopressin (AVP) are thought to function as modulators. Since AVP has been shown to influence pineal melatonin synthesis, the aim of the present study was to investigate the possible effects of the second hypothalamic nonapeptide oxytocin (OT), which likewise has been detected in the pineal gland. We therefore studied "synaptic" ribbon (SR) numbers, N-acetyltransferase (NAT) activity and the intracellular concentration of cyclic guanosine monophosphate (cGMP) following in vitro incubation of ra…
The effects of short pulses of light at night on numbers of pineal "synaptic" ribbons and serotonin N-acetyltransferase activity in male Sprague-Dawl…
1986
To characterize further the functionally enigmatic "synaptic" ribbons (SR) of the mammalian pineal gland and to study possible relationships to melatonin synthesis, in the present investigation rats were exposed to short pulses of light at night when both SR numbers and serotonin N-acetyltransferase (NAT) activity are high in comparison to day-time values. Male Sprague-Dawley rats were killed at 13:00 and 01:00 h, respectively, and at 01:10 and 02:00 h after exposure to light for 10 and 60 min, respectively. The pineals were rapidly taken out and cut sagittally in half. One half was processed for electron-microscopic quantitation of SR numbers and the other half for NAT determinations. It w…
Atypical 24-hour rhythms of serotonin N-acetyltransferase activity in the rat pineal gland.
1988
Previous long-term studies have shown that in the pineal gland of rats melatonin synthesis is subject to infradian rhythms with periods between 4 and 7 days. Since in these studies melatonin-related parameters were measured at one timepoint of a 24-hr cycle only, the aim of the present investigation was to extend these experiments by more frequent sampling, to characterize the infradian rhythmicity in more detail. Male Sprague-Dawley rats kept under a light schedule of LD 12:12 (lights on at 0700) were killed at 6-hr intervals on 8 consecutive days. After decapitation the pineal gland was rapidly dissected out, followed by measurements of one of the melatonin-forming enzymes, serotonin N-ac…
Synaptic ribbons of the rat pineal gland: responses to in-vivo and in-vitro treatment with inhibitors of protein synthesis.
1990
To elucidate the role of protein synthesis in the nocturnal increase of synaptic ribbons in the rat pineal gland, actinomycin-D, which inhibits transcription, and cycloheximide, an inhibitor of translation, were used. To assure that the drugs were effective and to relate morphological changes to pineal biosynthetic phenomena, the activity of N-acetyltransferase and levels of pineal indoleamine were measured. Results of in-vivo, short-term and long-term treatment with either drug suggest that transcription of proteins related to synaptic ribbon formation occurs during the first half of the light phase, whereas translation takes place during the first few hours of the dark phase. In contrast,…
Antidepressant and anxiolytic effects of alprazolam versus the conventional. antidepressant desipramine and the anxiolytic diazepam in the forced swi…
1992
The antidepressant and anxiolytic effects of alprazolam were compared to those of desipramine, diazepam and buspirone in the forced swim test. Subchronic alprazolam induced a reduction in immobility similar to that of desipramine in 'non-pretested' and 'pretested' rats. In 'non-pretested' rats, the anti-immobility effect of desipramine was potentiated by diazepam and alprazolam, given before subchronic desipramine, while the anti-immobility effect of subchronic alprazolam was counteracted by diazepam. Diazepam, administered before the pretest session, counteracted, 24 h later, the anti-immobility effect of subchronic desipramine and alprazolam; alprazolam counteracted the anti-immobility ef…
Using transdermal iontophoresis to increase granisetron delivery across skin in vitro and in vivo: effect of experimental conditions and a comparison…
2010
The objectives of the study were (i) to investigate the effect of experimental parameters on the iontophoretic transport of granisetron, (ii) to identify the relative contributions of electromigration (EM) and electroosmosis (EO), (iii) to determine the feasibility of delivering therapeutic amounts of drug for the treatment of chemotherapy-induced nausea and vomiting and (iv) to test the in vitro results in a simple animal model in vivo. Preliminary in vitro studies using aqueous granisetron formulations investigating the effect of drug concentration (5, 10, 20 and 40 mM) and current density (0.1, 0.2, 0.3 mA cm(-2)) were performed using porcine ear skin. As expected, cumulative delivery in…
Are the effects of the antidepressants amitriptyline, maprotiline, and fluoxetine on inhibitory avoidance state-dependent?
2005
Abstract State-dependent learning (SDL) is a phenomenon in which the retrieval of newly acquired information is possible if the subject is in the same physiological state as during the encoding phase. SDL makes it possible to separate the effects of drugs per se on learning from the effects due to changes in drug state during the task. The present work was designed to investigate whether the antidepressants amitriptyline (30 mg/kg), maprotiline (25 mg/kg), and fluoxetine (15 mg/kg) produce SDL of the inhibitory avoidance conditioning in male and female CD1 mice. In three separate experiments, independent groups were used for each pharmacological treatment and for each sex using a 2 × 2 expe…
Non-competitive inhibition of clomipramineN-demethylation by fluvoxamine
1995
The selective serotonin reuptake inhibitor fluvoxamine interferes with the metabolism of tricyclic antidepressants. The present investigation was set out to characterize these interactions in vitro using rat liver microsomes and in vivo by analysing levels of clomipramine and metabolites in sera of depressed patients treated concomitantly with fluvoxamine and clomipramine. Clomipramine was N-demethylated and hydroxylated in vitro by microsomes to N-desmethyl-clomipramine, 8-hydroxyclomipramine, and 10-hydroxyclomipramine. Kinetic analyses revealed Km values of 6.2 microM for N-demethylation and 1.2 microM for 8-hydroxylation. Fluvoxamine was a non-competitive inhibitor for N-demethylation w…