Quantitative determination of amorphous cyclosporine in crystalline cyclosporine samples by Fourier transform infrared spectroscopy.

The purpose of this study is the development of a quantification method to detect the amount of amorphous cyclosporine using Fourier transform infrared (FTIR) spectroscopy. The mixing of different percentages of crystalline cyclosporine with amorphous cyclosporine was used to obtain a set of standards, composed of cyclosporine samples characterized by different percentages of amorphous cyclosporine. Using a wavelength range of 450-4,000 cm(-1), FTIR spectra were obtained from samples in potassium bromide pellets and then a partial least squares (PLS) model was exploited to correlate the features of the FTIR spectra with the percentage of amorphous cyclosporine in the samples.

Cognitive allocentric representations of visual space shape pointing errors.

Subjects reached in three-dimensional space to a set of remembered targets whose position was varied randomly from trial to trial, but always fell along a "virtual" line (line condition). Targets were presented briefly, one-by-one and in an empty visual field. After a short delay, subjects were required to point to the remembered target location.

Analysis of pointing errors reveals properties of data representations and coordinate transformations within the central nervous system.

The execution of a simple pointing task invokes a chain of processing that includes visual acquisition of the target, coordination of multimodal proprioceptive signals, and ultimately the generation of a motor command that will drive the finger to the desired target location. These processes in the sensorimotor chain can be described in terms of internal representations of the target or limb positions and coordinate transformations between different internal reference frames. In this article we first describe how different types of error analysis can be used to identify properties of the internal representations and coordinate transformations within the central nervous system.

Basal ganglia and gait control: apomorphine administration and internal pallidum stimulation in Parkinson's disease.

Gait coordination was analyzed (four-camera 100 Hz ELITE system) in two groups of idiopathic Parkinson disease (PD) patients. Five patients underwent continuous infusion of apomorphine and were recorded in two different sessions (APO OFF and APO ON) in the same day. Three patients with a previous chronic electrode implantation in both internal globi pallidi (GPi) were recorded in the same experimental session with the electrodes on and off (STIM ON and STIM OFF).

Short-term memory for reaching to visual targets: psychophysical evidence for body-centered reference frames.

Pointing to a remembered visual target involves the transformation of visual information into an appropriate motor output, with a passage through short-term memory storage. In an attempt to identify the reference frames used to represent the target position during the memory period, we measured errors in pointing to remembered three-dimensional (3D) targets. Subjects pointed after a fixed delay to remembered targets distributed within a 22 mm radius volume.

Viewer-centered frame of reference for pointing to memorized targets in three-dimensional space.

Pointing to a remembered visual target involves the transformation of binocular visual information into an appropriate motor output. Errors generated during pointing tasks may indicate the reference frames used by the CNS for the transformation and storage of the target position. Previous studies have proposed eye-, shoulder-, or hand-centered reference frames for various pointing tasks, depending on visual conditions.

Electrophysiology of dopamine D-1 receptors in the basal ganglia: old facts and new perspectives.

1. The dopamine (DA) D1-receptor family is highly represented in the mammalian brain and particularly in the nigrostriatal system, whose integrity is crucial for the execution of motor performances. 2.

Activation of metabotropic glutamate receptors increase the frequency of spontaneous GABAergic currents through protein kinase A in neonatal rat hippocampal neurons.

1. The tight-seal whole cell recording technique was used to study the effects of the metabotropic glutamate receptor (mGluR) agonist, trans-1-aminocyclopentane-1,3-dicarboxylic acid (t-ACPD) on spontaneous gamma-aminobutyric acid (GABA)-mediated synaptic currents in neonatal rat CA1 hippocampal neurons in slices obtained from postnatal (P) days P6-P12. 2.

Outward potassium currents activated by depolarization in rat globus pallidus.

Voltage-dependent potassium currents play a key role in shaping the firing pattern of central neurons. Their pharmacological and physiological identification is rather important in the structures which are involved in the filtering of input/output messages. In this regard, globus pallidus external segment (GPe) is indicated as a crucial station in the well-known indirect pathway of the basal ganglia.

The modulation of dopamine receptors in rat striatum.

In the last decades, the contribution given by basic electrophysiology to the understanding of the nigrostriatal pathway in mammals has been rather important. The main results obtained by our group will be revised in this short review. The most common responses produced by dopamine (DA) on the principal striatal cells (the medium spiny neurons) are the modulation of the corticostriatal synaptic transmission and the decrease of voltage-dependent inward conductances.

Basic research in substantia nigra and ventral tegmental area: clinical implications.

In this review we will briefly examine some physiological and pharmacological aspects of the dopaminergic and non-dopaminergic cells of the midbrain in relationship to pathological conditions such as extrapyramidal disorders, mental illness, drug seeking behaviour and epilepsy.

Responses of rat mesencephalic dopaminergic neurons to a prolonged period of oxygen deprivation.

We employed intracellular electrophysiological techniques to examine the effects of a prolonged anoxia (more than 7 min superfusion with artificial cerebrospinal fluid saturated with 95% N2-5% O2) on dopaminergic neurons of the rat ventral mesencephalon maintained in vitro. A prolonged anoxia caused an inhibition of the spontaneous firing and a sustained (mean 16 min) and slowing declining hyperpolarization of the membrane in 30 dopaminergic cells. This was associated with a decrease of the apparent input resistance at 5, 10, 15 and 20 min of O2 deprivation by 38% (n = 18), 42% (n = 8), 48% (n = 18) and 54% (n = 8) of control, respectively.

Effects of dihydropyridine calcium antagonists on rat midbrain dopaminergic neurones.

1. The effects of the dihydropyridine calcium channel antagonists, nifedepine and nimodipine (300 nM-30 microM) were tested in vitro on intracellularly recorded dopaminergic neurones in the rat ventral mesencephalon. 2.

Developmental changes in spontaneous GABAA-mediated synaptic events in rat hippocampal CA3 neurons.

Ongoing spontaneous postsynaptic potentials (SPSPs) were intracellularly recorded at 34-36 degrees C from hippocampal CA3 neurons in slices obtained from postnatal days (P) 0-6 and 7-31. SPSPs occurred randomly, and their frequency distribution was fitted by a single exponential function. They were little affected by kynurenic acid, but were reversibly blocked by bicuculline, implying that they were mediated by GABAA receptors.

Effects of anoxia on rat midbrain dopamine neurons.

1. Dopamine-containing neurons of the rat midbrain were recorded intracellularly in vitro. Anoxia (2-5 min) caused reversible membrane hyperpolarization (4-25 mV), which blocked spontaneous firing of action potentials.

l-deprenyl test in migraine: neuroendocrinological aspects.

We evaluated the effect of l-deprenyl, a drug that increases the availability of endogenous dopamine, on the plasma levels of prolactin and growth hormone in 10 female patients with migraine and in 10 control subjects matched for age and menstrual phase. The patients showed a significant decrease in prolactin levels at 30, 60 and 120 min after the oral administration of 5 mg of l-deprenyl when compared with the values obtained in controls (p < 0.001).

Activation of metabotropic glutamate receptors induces an inward current in rat dopamine mesencephalic neurons.

To investigate the electrophysiological effects of the stimulation of the metabotropic excitatory amino acid receptors, we applied trans-1-amino-cyclopentane-1,3-dicarboxylate, an agonist of this type of receptors, on presumed rat dopamine cells intracellularly recorded in vitro. Trans-1-amino-cyclopentane-1,3-dicarboxylate (3-30 microM, t-ACPD) caused a sustained increase of the spontaneous firing rate and a depolarization. When the membrane potential was held at about the resting level (-50, -60 mV), by the single-electrode voltage-clamp technique, t-ACPD induced an inward current.

Neurotensin induces an inward current in rat mesencephalic dopaminergic neurons.

Neurotensin (0.3-3 microM) depolarized the membrane and increased the firing discharge of dopaminergic cells in slices of the rat mesencephalon. Under voltage-clamp, at holding potentials from -50 to -60 mV (near the resting membrane potential), neurotensin produced a sustained inward shift in the holding current.

A voltage-clamp analysis of NMDA-induced responses on dopaminergic neurons of the rat substantia nigra zona compacta and ventral tegmental area.

The effects of NMDA-receptor activation on dopaminergic neurons of the rat substantia nigra zona compacta and ventral tegmental area were studied by using in vitro intracellular electrophysiological recordings (current and voltage-clamp). NMDA depolarized the membrane and increased the firing activity. A voltage-dependent inward current and a reduction of the apparent input conductance were observed in voltage-clamp experiments.

Electrophysiological evidence for the presence of ionotropic and metabotropic excitatory amino acid receptors on dopaminergic neurons of the rat mesencephalon: an in vitro study.

The actions of the ionotropic and metabotropic excitatory amino acid agonists AMPA, quisqualate, kainate, NMDA and trans-ACDP were studied by means of intracellular electrophysiological recordings from dopaminergic neurons of rat mesencephalon in brain slices. It was observed that all these agents evoked an inward current in cells which were voltage-clamped near the resting potential (-50, -60 mV). The membrane responses produced by AMPA, kainate and quisqualate were associated with an increase of the apparent input conductance while the responses induced by NMDA and trans-ACDP were associated with a decrease in the apparent input conductance.

Electrophysiological effects of amineptine on neurones of the rat substantia nigra pars compacta: evidence for an inhibition of the dopamine uptake system.

1. Intracellular recordings were made from substantia nigra pars compacta neurones of the rat maintained in vitro in order to study the effects of the tricyclic antidepressant drug, amineptine. 2.

Nomifensine but not amantadine increases dopamine-induced responses on rat substantia nigra zona compacta neurons.

Responses of substantia nigra zona compacta neurons to nomifensine and amantadine were studied with intracellular recording techniques (current and voltage clamp) in in vitro slice preparation of rat mesencephalon. The application of nomifensine (1-10 microM) slightly hyperpolarized the cells and inhibited action potential discharge that occurs spontaneously. In voltage-clamp experiments (-50, -60 mV, holding potential) an outward current was observed.

GABA depolarizes neurons in the rat striatum: an in vivo study.

GABA, applied by iontophoresis to striatal neurons of the rat in an in vivo preparation, depolarized the membrane potential and decreased the input resistance in a dose-dependent manner. The null potential of the GABA depolarization was about -50 mV. In addition, a fading of the GABA-induced response was observed for prolonged and relatively high amino acid application.