Biomedical subjects

Tahira Perveen

Publications and source records attributed to Tahira Perveen.

8 recordsLinked to original sources

PubMed2006

Relationship of brain tryptophan and serotonin in improving cognitive performance in rats.

Brain function can be affected by the availability of dietary precursors of neurotransmitters. The diet induced increase in tryptophan (TRP) availability has been shown to increase brain serotonin synthesis and various related behaviors. Evidence shows that TRP and serotonin (5HT; 5 Hydroxytryptamine) play a significant role in memory function. Enhanced brain serotonin activity has been shown to improve cognitive performance in animals and human whereas decreasing brain 5HT levels by acute TRP depletion has been shown to impair cognition. A number of methods have been used for the assessment of memory in animals. In the present study, the radial arm maze and the passive avoidance was used for the assessment of memory in rats following long-term TRP administration. TRP at doses of 50 and 100 mg/kg body weight was orally administered for 6 weeks. The present study shows a significant improvement in memory of rats following both doses of tryptophan. Plasma TRP, brain TRP, 5HT and 5 hydroxy indol acetic acid (5HIAA) levels were increased significantly following administration of TRP. The results of the present study suggest that increase in brain 5HT metabolism following long term TRP administration may be involved in enhancement of memory.

Animals↗

PubMed2006

Increased serotonergic functions following adminstration of 1-(1-naphthyl) piperazine in propranolol injected rats.

Propranolol a beta adrenergic antagonist, binds with 5-HT1 receptor. 1-(1-naphthyl) piperazine (1-NP) a derivative of quipazine has serotonin antagonist activity at 5-HT2 and agonist activity at 5-HT1 site. In the present study neurochemical and behavioral effects of 1-NP was monitored in saline and propranolol injected rats. 1NP increased locomotor activity in saline as well as in propranolol injected rats. Administration of propranolol also increased locomotor activity and these increases were more enhanced following 1-NP administration. Levels of 5-HT were not altered following the administration of 1NP in saline as well as propranolol injected rats. 5-HT turnover however decreased by the administration of propranolol Adminstration of 1NP decreased 5-HT turnover in saline but not in propranolol injected rats.

Adrenergic beta-Antagonists↗

PubMed2005

Repeated administration of lead decreases brain 5-HT metabolism and produces memory deficits in rats.

Long-term exposure to low levels of lead (Pb2+) has been shown to produce learning and memory deficits in rodents and humans. These deficits are thought to be associated with altered brain monoamine neurotransmission. Increased brain 5-HT (5-hydroxytryptamine; serotonin) activity is thought to be a prerequisite for maintaining control over the cognitive information process, and is said to have a role in learning and memory. This study was designed to investigate the effects of Pb2+ administration on brain 5-HT metabolism and memory function in rats. Rats were injected daily for three weeks with Pb2+-acetate at a dose of 100 mg/kg body weight. The assessment of memory was done using the Radial arm maze (RAM) and Passive avoidance tests. The results showed spatial working memory (SWM) deficits as well as decreased brain 5-HT metabolism. Increased serotonin activity is considered to be an indication of improved cognitive performance. The results are discussed in the context of lead-induced decreases in 5-HT metabolism playing a role in the impairment of memory.

Animals↗

PubMed2004

Lack of restraint-induced increases of brain serotonin metabolism in rats treated with spiperone: relationship with restraint-induced behavioral deficits.

Spiperone is a potent dopamine (DA) D2, serotonin (5-hydroxy tryptamine, 5-HT) 5-HT(1A) and 5-HT(2A) antagonist. It is used clinically as an antischizophrenic compound. Previous studies have shown that a downregulation of somatodendritic 5-HT(1A) receptor is involved in adaptation to stress. The present study was designed to investigate the effects of spiperone administration on behavioral adaptation to an episode of restraint stress and on brain serotonin metabolism. Spiperone was administered to rats at a dose of 0.25 mg/kg/ml two times a day for two days. Saline or spiperone treated rats were restrained for 2 h on day 2. Effects of restraint on food intake, water intake, growth rate, plus maze and open field activity were monitored on next day. All animals were killed after a restraint period of 2 h on the 3rd day. An episode of 2 h restraint decreased food intake, growth rate and water intake comparably in saline and spiperone treated rats. Open field activity was not altered by restraint stress or spiperone treatment. Plus maze activity decreased by restraint stress in saline but not spiperone treated rats. 5-HIAA levels increased in saline but not spiperone treated rats. The findings are discussed in the context of a role of serotonin and 5-HT(1A) receptor antagonism in adaptation to stress.

Journal Article↗

PubMed2003

Decrease of ethanol intake following repeated injection of serotonin-1A agonist in rats: relationship with receptor responsiveness.

OBJECTIVE: To monitor pre and postsynaptic receptor responsiveness and consumption of ethanol following the repeated administration of a selective serotonin-1A receptor agonist, 8-hydroxy-2-di-n-propylaminotetralin (8-OH-DPAT), to ethanol treated rats. DESIGN: The experimental protocol was designed to administer ethanol orally to rats for three weeks and 8-OH-DPAT during the 3rd week. PLACE AND DURATION OF STUDY: The experiments were performed in the department of Biochemistry, Karachi University. Samples collected after three weeks of treatment were analyzed within a week. SUBJECTS AND METHODS: The study was conducted on 24 males albino Wistar rats treated with ethanol for three weeks. 8-OH-DPAT at a dose of 1mg/kg or saline was injected to ethanol treated rats from day 1 to day 5 during the 3rd week to monitor the effects on ethanol consumption. Pre and postsynaptic responses to 8-OH-DPAT were monitored by injecting the drug on the 6th day to a group of 5-day saline and a group of 5-day 8-OH-DPAT injected animals. Control animals of the two groups were injected with saline. RESULTS: Before the injection of 8-OH-DPAT, weekly intakes of ethanol were highly comparable in the two groups. Administration of 8-OH-DPAT, from day 1 to day 5, decreased ethanol intake. Pre and postsynaptic serotonin-1A receptor dependent responses monitored on the 6th day were higher in 5-day saline than 5-day 8-OH-DPAT injected animals. CONCLUSION: A decrease in the effectiveness of negative feedback control over the synaptic availability of serotonin following 5-day administration of 8-OH-DPAT is involved in the decreases of ethanol consumption.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2003

Effects of 2 hrs. restraint stress on brain serotonin metabolism and memory in rats.

Stress is a non-specific response of body to any physiological and psychological demand. Studies on experimental animals show that uncontrollable stress situation produce neurochemical and behavioral deficits In the present study effects of 2 hrs. restraint stress were monitored on brain serotonin metabolism and memory in starved rats. An episode of 2 hrs. restraint stress exhibited a significant decrease in food intake as well as in growth rate in starved rats. The memory function was significantly enhanced following 2 hrs. restraint stress in starved rats. The concentration of Noradrenaline (NA) and Dihydroxyphenyl acetic acid (DOPAC) were increased in the brain while no effect of restraint stress was observed on brain Dopamine (DA) level. Brain levels of 5-hydroxy indoleacetic acid (5-HIAA) was significantly decreased in restraint rats. Tryptophan levels in brain as well as in plasma significantly decreased in starved rats following 2 hrs. restraint stress. The findings are explained in terms of enhanced memory function following restrained stress which may be associated with a decrease in serotonergic function in starved rats.

Journal Article↗

PubMed2003

Injected tryptophan increases brain but not plasma tryptophan levels more in restrained rats.

Immobilization stress given for one hour decreased cumulative food intake and growth rate in rats. Activity in an open field scored next day was also smaller in the restrained animals. Stress is known to enhance brain serotonin (5-hydroxytryptamine; 5-HT) metabolism. It is however not clear, whether this enhancement is caused by an increase in the activity of tryptophan hydroxylase, the rate limiting enzyme of 5-HT biosynthesis or availability of the precursor tryptophan to the brain. In order to determine the utilization of tryptophan via serotonin path way in brain during stress; rats were injected with saline or tryptophan (50 mg/kg, i.p.). A group of both saline and tryptophan injected animals was restrained for one hour, while another group left unrestrained. The animals were killed immediately after the termination of stress period to collect plasma and brain samples. Injected tryptophan resulted in 3-4 fold rise of plasma tryptophan in both unstressed and stressed animals in one hour. Stress alone however had no effect on plasma total tryptophan concentration. Free tryptophan in plasma, brain tryptophan, 5-HT and 5-hydroxyindole acetic acid (5-HIAA) all increased by both stress and tryptophan injection. The increases of brain tryptophan, 5-HT and 5-HIAA but not of free tryptophan in plasma were considerably greater in restrained animals given tryptophan load. The results suggest that enhancement of brain serotonin metabolism during stress is caused by an increase in the availability of tryptophan to the brain as well as an increase in the activity of the enzyme tryptophan hydroxylase. Factors affecting the availability of tryptophan to the brain are discussed.

Journal Article↗

PubMedDate not supplied

Inhibition of restraint-induced neuroendocrine and serotonergic responses by buspirone in rats.

The effects of buspirone (0.5 mg/kg) on the neuroendocrine and serotonergic responses to stress were monitored in rats. Exposure to 2-h of restraint stress increased circulating levels of corticosterone, noradrenaline and glucose. The metabolism of 5-hydroxytryptamine (5-HT; serotonin) increased in the brain. Prior administration of buspirone did not alter levels of corticosterone, noradrenaline and glucose in unrestrained rats, but inhibited stress-induced increase in the activity of hypothalamic-pituitary-adrenal (HPA) axis and circulating levels of glucose. Restraint-induced rise in brain 5-HT and 5-hydroxyindole-acetic acid (5-HIAA) was also attenuated by buspirone. Unrestrained animals injected with buspirone also exhibited a decrease in brain 5-HIAA concentration. The findings are discussed in the context of the role of somatodendritic 5-HT(1A) receptors in responses to stress.

Animals↗