Search results for "LPI"

Lack of autoreceptor mediated regulation of the spontaneous dopamine turnover in the isolated neurointermediate lobe of the rat pituitary gland in vi…

1990

Isolated neurointermediate lobes of the rat pituitary gland were incubated in Krebs-HEPES solution and the spontaneous outflow of endogenous dopamine and its metabolites (DOPAC, HVA and MOPET) was determined by HPLC with electrochemical detection. The spontaneous outflow of dopamine metabolites (about 1500 fmol/10 min) largely exceeded that of dopamine (about 60 fmol/10 min). Apomorphine concentration-dependently (IC50, 205 nmol/l) reduced the spontaneous outflow of the dopamine metabolites. The effect of apomorphine developed slowly and was progressive over an observation period of 70 min. After 1 h of exposure to a maximall effective concentration of apomorphine (10 mumol/l), the outflow …

Relaxant effect of dopamine on the isolated rat uterus.

1988

The effect of dopamine was studied on the isolated uterus of diethylstilboestrol-treated rats. Dopamine, at concentrations (10(7)-10(-4) M) produced a concentration-dependent relaxation in the K+-depolarized rat uterus. On a molar basis, dopamine was about 500 times less potent than adrenaline in relaxing the uterus, the maximum degree of relaxation obtained with both drugs was the same. Pretreatment of the rats with reserpine (5 mg/kg) did not produce any modification of the dose-response curve to dopamine. Similarly, cocaine (3 x 10(-6) M) failed to modify the relaxant effect of dopamine. The dopamine induced relaxation was inhibited by propranolol (10(-9)-10(-7) M) in a dose-dependent ma…

Response to dopamine agonists of the rat isolated uterus.

1993

1. Quinpirole did not produce any effect in isolated uterus from oestrogenized rats even when it is contracted by KCl (37 mM). 2. Fenoldopam produced a relaxant effect on rat isolated uterus contracted by KCl which was not significantly modified by SCH 23390. 3. Reserpine decreased the effect of the lowest doses of fenoldopam. In reserpinized rats, propranolol (10(-9), 10(-8), 10(-7) M) antagonized the effect of the lowest doses of fenoldopam and neither SCH 23390, sulpiride nor ranitidine modified the effect of fenoldopam. 4. The results confirm our previous finding that DA1-receptors are not functional in our preparation. The effect of fenoldopam was partially due to a catecholamine-relea…

D2-dopamine receptor blockade modulates temporal resolution in goldfish.

2002

A possible effect of dopamine on the temporal resolution of goldfish was investigated in a behavioral, two-alternative, forced-choice procedure. Flicker fusion frequency (FFF) was measured before and after bilateral intravitreal injections of D1- or D2-dopamine receptor (D1-/D2-R) antagonists, or after depletion of retinal dopamine by bilateral intravitreal injections of the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA). Prior to drug injections, fish achieved FFFs of 33–39 Hz. A D1-R antagonist, SCH 23390, reduced FFF by about 12% (P > 0.1), whereas a D2 antagonist, sulpiride, reduced the relative FFF by 25% (P < 0.03). Depletion of retinal dopamine with 6-OHDA induced a gradual…

Effects of Sulpiride Treatment on the Hypothalamic Supraoptic and Paraventricular Nuclei

2009

Addition of NMDA-receptor antagonist MK801 during oxygen/glucose deprivation moderately attenuates the upregulation of glucose uptake after subsequen…

2011

During stroke the blood–brain barrier (BBB) is damaged which can result in vasogenic brain edema and inflammation. The reduced blood supply leads to decreased delivery of oxygen and glucose to affected areas of the brain. Oxygen and glucose deprivation (OGD) can cause upregulation of glucose uptake of brain endothelial cells. In this letter, we investigated the influence of MK801, a non-competitive inhibitor of the NMDA-receptor, on the regulation of the glucose uptake and of the main glucose transporters glut1 and sglt1 in murine BBB cell line cerebEND during OGD. mRNA expression of glut1 was upregulated 68.7- fold after 6 h OGD, which was significantly reduced by 10 μM MK801 to 28.9-fold.…

Dopaminergic modulation of evoked vasopressin release from the isolated neurohypophysis of the rat

1982

1. Neurointermediate lobes of rat pituitaries were incubated in Locke or Krebs solution, and the vasopressin released into the medium was assayed on the blood pressure of the pithed rat or by a radioimmunological procedure. Release of vasopressin over resting levels was evoked either by incubation with 60 mM KCl (high K) solution or by electrical stimulation of the pituitary stalk. Two different kinds of electrical stimulation were carried out. Procedure A (1 ms, 10 Hz, 5 times for 1 min within 10 min) induced a vasopressin overflow which was greatly calcium-dependent but only insignificantly sensitive to tetrodotoxin (TTX). Procedure B (0.2 ms, 15 Hz, 10 s trains with 10 s intervals for 10…

Intrinsic activation of GABAA receptors suppresses epileptiform activity in the cerebral cortex of immature mice

2010

SUMMARY Purpose: Activation of ionotropic c-aminobutyric acid type A (GABAA) receptors induces in immature neocortical neurons a membrane depolarization that may contribute to the higher epilepsy susceptibility in newborns. To elucidate whether depolarizing GABAergic responses enhance or attenuate epileptiform activity in the immature neocortex, we investigated the effect of agonists, antagonists, and positive modulators of GABAA receptors on epileptiform activity. Methods: We performed in vitro field potential recordings on isolated whole neocortex preparations and whole cell recordings of identified pyramidal neurons in 400-lm slices of immature (postnatal day 1–7) mice. Epileptiform acti…

Behavioural responsiveness to picrotoxin and desipramine in adult rats prenatally exposed to different benzodiazepine receptor agonists

1995

The behavioural responsiveness to picrotoxin and desipramine was investigated in adult rats prenatally exposed to different benzodiazepine receptor agonists such as diazepam, alprazolam and zolpidem. Prenatal exposure to diazepam and alprazolam similarly potentiated the anti-immobility effect on the forced swimming test and the inhibitory effect on spontaneous motor activity of picrotoxin and desipramine and increased the seizure sensitivity to picrotoxin. Prenatal zolpidem seems to be ineffective. These data suggest that, despite the differences in their pharmacodynamic profile, prenatal exposure to diazepam and alprazolam, but not zolpidem, may have similar permanent consequences on the b…

The Effects of Epinine on Arterial Blood Pressure and Regional Vascular Resistances in Anesthetized Rats

1998

1. We carried out experiments in anesthetized rats to study the hemodynamic effects of intravenous injections of epinine. 2. Epinine (1-320 micrograms/kg) produced a biphasic effect on mean arterial blood pressure (n = 30). At doses lower than 40 micrograms/kg, arterial blood pressure decreased (by as much as 21.5 +/- 3.4%), though at higher doses it increased dose dependently (by as much as 73.2 +/- 14.5%). Epinine also produced bradicardia in a dose-dependent manner (by as much as 26.4 +/- 4.9%). Sulpiride (100 micrograms/kg) suppressed the hypotensive effect of epinine but did not change the hypertensive effect. In the presence of prazosin (1,000 micrograms/kg), arterial blood pressure r…