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Biomedical subjects

T H Yin

Publications and source records attributed to T H Yin.

At least 19 recordsLinked to original sources
PubMed1996

Serotonergic serotonin 2 receptor modulation on DOPAC and 5-HIAA levels in rat striatum and nucleus accumbens: microdialysis studies of freely moving rats.

1. In vivo microdialysis with microbore-HPLC/ECD was employed to examine and compare changes of monoaminergic metabolites, dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) in the nucleus accumbens (NuAc) and the neostriatum (Str) of freely moving rats, following systemic administration of the specific 5-HT(2) analogue. 2. The 5-HT(2) agonist decreased DOPAC and 5-HIAA in both the NuAc and Str. However, the effect produced by apomorphine only decreased the DOPAC level in these two areas. 3. This effect did not occur in the rats that had been pretreated with the serotonin (5-HT) depleting agent. However, the effect was found in the rats that the striatal neurons had been damaged. 4. The 5-HT(2) effect regulated the mesencephalic dopamine (DA) synthesis/turnover only when entirely influenced by 5-HT. The striato-nigral feedback loop was not involved in this effect. Additionally, presynaptic relationship probably occurred between the 5-HT and its innervated DA pathways.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Morphine withdrawal and schedule-induced polydipsia.

Schedule-induced polydipsia (SIP) is the characterized behavior for reducing the heightened arousal in a schedule of intermittent feeding. In the present study, SIP rats received an incremental doses of morphine in repeated treatments on the first 5 days and were then challenged by naloxone on the 6th day. We examined the SIP performance during morphine dependence and withdrawal. The roles of the locus coeruleus (LC) and excitatory amino acid (EAA) pathways were examined by bilateral LC lesions and lateral ventricle kynurenic acid infusion. In each manipulation, the level of water intake was recorded as an index of SIP strength. Our results showed that morphine dependence reduced SIP strength, whereas withdrawal initially reduced but then elevated SIP strength. Such effects were attenuated by bilateral LC lesions or kynurenic acid administration. The implications of these results on morphine withdrawal reaction and SIP performance were discussed.

Animals↗
PubMed1995

Schedule-induced polydipsia increased both mesotelencephalic-dopaminergic and pontine-noradrenergic activities in the rat brain.

We have demonstrated previously that the activity of schedule-induced polydipsia (SIP) was persistently depressed after successive lesions of the bilateral symmetrical locus coeruleus and the ventral tegmental area. The hypothesis that central catecholaminergic neurons mediate animal behaviors in arousal or coping processes, e.g., SIP, was tested by the demonstration of concomitant changes of transmissions in regions of appropriate nerve terminals. By using the high performance liquid chromatography coupled with electrochemical detection methods, the current experiments were designed to examine the regional turnover of monoamines in the performance of SIP of the control rats by measurements of the biochemical derivatives including dopamine (DA), norepinephrine (NE), serotonin (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), dihydroxyphenylalanine (DOPA), 4-hydroxy-3-methoxyphenylglycol-4-sulfate (MHPG-SO4) and 5-hydroxyindoleacetic acid (5-HIAA). It was found that rats in the performance of SIP, the DA levels and DA synthesis and utilization in the limbic area were increased and that the NE level and NE synthesis in the several pontine NE projected areas, e.g., limbic area, hippocampus, cortex and pons were also increased. Conversely, both NE and 5-HT metabolism in the hippocampus and the cortex were decreased. We concluded that the enhanced actions of the DA-limbic system and NE-pontine system in the rats are both important for the maintenance of SIP performance.

Animals↗
PubMed1994

Effects of amperozide on schedule-induced polydipsia in rats.

Schedule-induced polydipsia occurs when food-deprived rats are exposed to a fixed-interval feeding schedule (FI = 60 s) for 1 h every day. Amperozide, a novel antipsychotic drug with a strong affinity for the 5-HT2 receptor, was injected i.p. after completion of the requisite training sessions. The experimental rationale is that although the intensity of licking behavior in schedule-induced polydipsia can be taken as an index for anxiety, the drug-induced motor dysfunction should be assessed. In experiment 1, we tested the effect of amperozide on schedule-induced polydipsia at doses of 2, 4, and 8 mg/kg. The data showed that each dose significantly diminished the amount of licking and water intake. The number of presses decreased only at the dose of 8 mg/kg. During five post-treatment daily sessions for 5 days, these three measures returned to normal levels except that the number of pellets earned during the sessions did not significantly change. In addition, the number of presses showed a rebound after the termination of amperozide administration. In experiment 2, in addition to the total water intake, number of licks, pellets earned and presses, we also analyzed the postpellet temporal variation in the number of licks and presses in each schedule-induced polydipsia session. The drug was stopped for one day after each dose of 0.2, 0.4, 0.8 and 1.6 mg/kg of amperozide. The data showed that doses from 0.2 to 0.8 mg/kg did not alter any measure in drug-treated sessions and that the dose of 1.6 mg/kg decreased the number of licks and water intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of prefrontal cooling on levels of glutamate, DOPAC and 5-HIAA in nucleus accumben and striatum in vivo.

The effect of pre-frontal cooling of the cortex (PFC) on monoaminergic metabolites (DOPAC and 5-HIAA) and excitatory amino acids (glutamate (Glu) and aspartate (Asp)) was investigated using microdialysis in rat striatum (Str) and nucleus accumben (NuAc). The cooling profoundly decreased Glu and elevated DOPAC and 5-HIAA in both Str and NuAc for a long period of time. However, the time course of the detection of each compound appeared different between Str and NuAc. In NuAc, Glu decreased rapidly to reach the plateau in about 30 min; however, in Str, Glu decreased steadily and reached the plateau in about 60 min. The time courses of elevation of 5-HIAA and DOPAC were also quite different between Str and NuAc; there was more profound change observed in Str than in NuAc. The level of DOPAC exhibited a similar period of increase (7.14 min) in NuAc and Str but in NuAc it decreased toward the baseline much earlier (about 2h) than Str (over 3 h). The level of 5-HIAA in Str showed a period of rapid increase to a plateau (less than 42 min) but a trend of decrease started before the termination of sampling. In NuAc, in contrast, 5-HIAA increased slowly (more than 48 min) and maintained a plateau until termination of sampling. We conclude that PFC cooling may have caused an increase in Glu secretion and resulted in the release of the tonic restraint on DA terminals in both Str and NuAc, thus increases the synaptic turnover of monoamines.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Role of locus coeruleus and serotonergic drug actions on schedule-induced polydipsia.

Schedule-induced polydipsia (SIP) poses a general buffering property to reduce the heightened arousal produced by a schedule of intermittent feeding. It thus provides a unique opportunity to study CNS integration in stress-coping reactions. In the present study, we examined the role of the locus coeruleus (LC) and the pharmacological actions of serotonergic (5-HT2) analogs on SIP. Water intake, licking, and bar presses per minute in rats were recorded as indices of SIP activity after they had been subjected to 1-h performance of a fixed-interval 1-min operant pellet conditioning. Our results showed that SIP was progressively decreased after lesions were placed bilaterally in the LC areas and then followed by further lesioning in the bilateral ventral tegmental area. Neurotoxin DSP-4 also had an inhibitory action on the SIP potency. In addition, SIP was attenuated by 2,5-dimethoxy-4-iodoamphetamine (0.1, 0.5, or 1.0 mg/kg, IP), a 5-HT2 agonist, and activated by ritanserin (2.5 mg/kg, IP), a 5-HT2 agonist. After bilateral LC lesions, SIP was attenuated and the activating effect of RIT was abolished. Our data suggest that the LC is involved in the central integration of SIP and that the modulating effects of 5-HT2 receptors on SIP depend upon the integrity of LC function.

Animals↗
PubMed1992

Reduction of blood PO2 decrease and PCO2 increase during asphyxia by paramedian reticular nucleus in cats.

Effects of activation of paramedian reticular nucleus (PRN) on the systemic arterial blood pressure (SAP), heart rate, renal nerve activity (RNA), and changes of the partial pressure of the arterial blood oxygen (PO2) and carbon dioxide (PCO2) during asphyxia were studied in cats anesthetized with chloralose (40 mg/kg) and urethane (400 mg/kg). During a 35-s period of asphyxial anoxia, SAP and RNA increased while heart rate decreased significantly. The arterial blood PO2 decreased by 64.6 +/- 4.7% while the PCO2 increased by 54.6 +/- 6.3%. Electrical stimulation of PRN produced a mild to moderate decrease of the SAP, heart rate, and RNA, but arterial PO2 and PCO2 did not change significantly. When PRN was stimulated simultaneously with asphyxia, increases of SAP and RNA and changes of blood gases subsequent to asphyxia reduced significantly. Arterial PO2 decreased only 54.0 +/- 4.9% while the PCO2 increased 39.4 +/- 10.5% (p < 0.01). Similar effects were observed in the venous blood from inferior vena cava. In addition, when the arteriovenous difference of PO2 and PCO2 was compared, simultaneous PRN stimulation during asphyxia produced a higher PO2 reserve (66.3%) and less PCO2 production (-7%) than without PRN stimulation; PO2 54.2%, PCO2 (-2.9%). The results suggest that PRN is a structure that can exert inhibition over a wide spectrum of body functions; not only autonomic system but probably also metabolism.

Animals↗
PubMed1990

The role of atrial natriuretic factor in dehydration and schedule-induced drinking behaviour.

Dehydration-induced drinking (DID) has been defined as a type of homeostatic behaviour controlled by factors related to water balance, whereas schedule-induced polydipsia (SIP) is considered to be a type of nonhomeostatic drinking subsequent to a general increase in motor excitability. In this study, we have attempted to assess the role of atrial natriuretic factor (ANF) in both models to elucidate the mechanisms controlling water intake. Intracerebroventricular injection of ANF (2-8 nmol) caused a dose related suppression of water intake in both DID and SIP, but intravenous injection with a higher dose of ANF (8 nmol) produced a significant suppression of water intake only in DID. Before drinking started, tissue ANF levels increased in atria in both models and decreased in hypothalamus in DID but not in SIP. After 1 hour of drinking, ANF levels decreased in atria in both models and increased in hypothalamus in SIP but not in DID. These results suggest that DID and SIP are different in their thirst regulation, and that the notion that peripheral ANF serves as a humoral factor sending signals to central in the fluid homeostatic control mechanism is questionable.

Animals↗
PubMed1988

Effects of lateral and medial septal lesions on various activity and reactivity measures in rats.

Roles of the lateral and medial septum in the regulation of activity, reactivity and open field behavior in rats were examined in the present study. Effects of lateral, medial and combined lateral and medial septal lesions were studied, respectively. Our results indicate that lateral septal lesions significantly decreased locomotor activity and tended to decrease rearing response. While it also markedly increased movement time in the activity monitor, stereotyped behavior and tactile startle amplitude. The most significant findings with medial septal lesions were decreased activity, especially in the center area of an open field and decreased exploratory behavior in rats. For most behavioral measures, effects of combined lateral and medial septal lesions were similar to that of medial septal lesions alone except that it augmented startle response with a different response pattern compared to that of lateral septal lesions alone. The locomotion patterns of these animals also revealed some qualitative difference in their behavior. These results are further discussed in the scope of anatomical, neurochemical and pharmacological differentiations of the septum complex.

Animals↗
PubMed1987

Adenosine in hemorrhagic shock: possible role in attenuating sympathetic activation.

Changes in plasma purine nucleoside level, autonomic activity and hemodynamic reactions were studied in pentobarbital anesthetized rabbits during hemorrhagic shock. Shock was elicited by bleeding the animals to a mean blood pressure of 40 mmHg and maintained until 60% of the maximum bleeding volume in the reservoir had been taken up spontaneously. The remaining shed blood was reinfused thereafter. Norepinephrine (NE), epinephrine (E), adenosine (AD) and uric acid were measured by HPLC with electrochemical detection, fluorometry or UV absorbance. The results showed hemorrhagic shock caused a significant rise in plasma NE, E, AD, and uric acid levels, but the magnitudes and time profiles were different among them. Plasma NE and E increased during the shock compensatory period then declined in the decompensation period whereas adenosine and its metabolite uric acid were elevated persistently during both periods. It is concluded that a balance between autonomic activity and tissue metabolism is important in the maintenance of hemodynamics during shock.

Adenosine↗
PubMed1987

Clonidine suppression and its adrenoreceptor mediation in schedule-induced polydipsia.

Rats were trained in a fixed-interval, one-minute (FI 1 min) food reinforcement schedule for 1 hour daily at reduced body weight until their lever presses, licks and water intake all became stabilized for 6 days. Two experiments were performed to examine the function of sympathetic activity in schedule-induced polydipsia. In experiment 1, intracerebroventricular injection of clonidine (0.75-37.5 nmol) produced a dose-related suppression of schedule-induced drinking and licking and schedule-dependent lever pressing; these effects were later attenuated by yohimbine (5 nmol) pretreatment. Prazosin (10 nmol) also decreased clonidine-induced suppression of lever pressing, whereas neither prazosin (10 nmol) nor naloxone (10 nmol) caused any alteration in the suppression effects of clonidine on drinking and licking. None of these antagonists alone changed an individual rat's preestablished behavioral baselines. In experiment 2, the endogenous catecholamine levels, were determined in frontal cortex, hypothalamus, brainstem, dorsal obex area and adrenal glands. During the SIP situation, both the epinephrine level in adrenal glands and the norepinephrine level in hypothalamus were elevated.

Adrenal Medulla↗
PubMed1986

Effects of intraportal glucagon administration concurrent to feeding on meal pattern and hepatic glycogen content in the rat.

Effects of intraportal influsion of glucagon in vehicle concurrent to feeding on meal pattern were studied in rats with reference to the changes of glycogen content in the liver. The feeding of the animal was monitored by an eatometer in the test chamber. The removal of a Noyes peller, 45 mg, in the food trough activated both a food dispensor to deliver another one and an infusion pump to infuse fluid into the hepatoportal vein at a rate of 0.35 ml/min for 30 sec. The infusion pump was on active state 23 hr/day for consecutive 15 days with a sequence: saline from 1st to 5th day, glucagon in saline (3 micrograms/ml) from 6th to 12th day, and again saline from 13th to 15th day. During the experiment, 7 groups of 5 rats in each were sacrificed at different times for determination of the glycogen content of the liver and the glucose level in the hepatic and hepatoportal veins. The data of 10 rats that proceeded up to the 12th day of infusion and those of 5 that continued to complete the whole course of 15 days infusion were used for analysis of meal pattern. The results revealed that the food intake was uniformly depressed during the period of glucagon administration and that the reduced food intake was totally accounted for by the premature termination of meals. The hepatic glycogen was depleted with glucagon initially but tended to come back with time. However, hepatic hyperglycemia was maintained without abating.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗