Persistent effects of amphetamine on cerebellar Purkinje neurons following chronic administration

The spontaneous discharge of cerebellar Purkinje neurons was studied in rats after withdrawal from chronic treatment with amphetamine (2 mg/kg per day x 21 days). Discharge rates in withdrawn animals remained significantly lower than those of controls for up to 50 days. Disruption of the adrenergic input to these neurons from the locus coeruleus by treatment with propranolol, clonidine or reserpine, partially restored these discharge rates. Acute administration of amphetamine in amphetamine-withdrawn rats did not further depress Purkinje neurons discharge rate, whereas in a previous study in this lab, Purkinje neurons from naive animals were markedly slowed. Moreover, Purkinje neurons from amphetamine-withdrawn rats were also significantly less sensitive than controls to locally applied norepinephrine. These results demonstrate that chronic amphetamine can lead to very long-term changes in neuronal activity, and suggest that these changes may be mediated, in part, by the noradrenergic transmitter systems.     

Laser doppler flowmetry. A new non-invasive measurement of microcirculation in intensive care?

Laser doppler flowmetry (LDF) is a new non-invasive technique by which microcirculation changes in tissue can be studied. In recent papers, this technique has been used to measure microflow in standardized fluid models, in animals and in human clinical situations. LDF utilizes the doppler shift, i.e. the frequency (wave length) change that light as well as all waves undergo being reflected by moving objects such as, e.g. red blood cells. A beam of low power laser light (2 mW He-Ne at 632.8 nm) is led by an optical fibre to a measuring head. From here it enters the tissue to which it is applied by a hemisphere with a 1 mm radius. Blood cells traversing this volume are struck by the light and reflect it, whereby the light undergoes a doppler shift. The surrounding tissue also reflects the light, but in an unshifted manner. Thus the volume of illumination is a mixture of an unshifted and a doppler shifted component, the magnitude and frequency of the latter being related to the number of moving cells and their velocity. The measured microflow is proportional to an arbitrary scale (0 to 10). Our own experience with some applications in human clinical situations is described: Normal skin in a control group. Normal skin and burned area in burned patients. Patient in hypothermia with general anesthesia. Patient in shock. LDF seems to be an interesting new non-invasive technique, supplying a good definition of the skin microflow. In the future, this technique could be one of the non-invasive techniques used for intensive care, defining the microcirculation state of a patient.     

The role of ferritin and hemosiderin in the MR appearance of cerebral hemorrhage: a histopathologic biochemical study in rats.

A rat model of cerebral hemorrhage using stereotaxic injection of blood into the right basal ganglia was developed to investigate the influence of iron metabolism on the appearance of cerebral hemorrhage on MR images. Images of in vitro fixed brain sections stained specifically for different iron-storage substances, ferritin and hemosiderin, created by digitization of the pathology sections using an Eikonix CCD camera, were compared with the in vivo MR images of late-phase hematomas. Areas of the pathologic and MR features of the lesions were quantitatively correlated. The single-slice MR images were obtained with the use of T1- and T2-weighted spin-echo pulse sequences, as well as T2-weighted spin-echo pulse sequences in which the 180 degrees refocusing pulse was offset from the center of the echo time; this was termed an asymmetric spin-echo pulse sequence. The symmetric and asymmetric T2-weighted images allowed the calculation of line-width images, which emphasize line broadening from intravoxel magnetic field inhomogeneities that arise from the presence of iron-containing substances. From biochemical and histochemical staining, we conclude that at least two iron-storage substances are present in the late phase of resolving cerebral hematomas. Ferritin has a wider distribution than hemosiderin, showing a similar distribution to the MR signal changes of the calculated line-width images. Line-width mapping is a sensitive means of detecting magnetic field inhomogeneities caused by the magnetic susceptibility differences introduced by the aggregation of these iron-storage substances.