Intracranial Injection of an Optogenetics Viral Vector Followed by Optical Cannula Implantation for Neural Stimulation in Rat Brain Cortex.

Optogenetics is rapidly gaining acceptance as a preferred method to study specific neuronal cell types using light. Optogenetic neuromodulation requires the introduction of a cell-specific viral vector encoding for a light activating ion channel or ion pump and the utilization of a system to deliver light stimulation to brain. Here, we describe a two-part methodology starting with a procedure to inject an optogenetic AAV virus into rat cortex followed by a second procedure to surgically implant an optical cannula for light delivery to the deeper cortical layers.

Long-lasting effects of neonatal ionizing radiation exposure on spatial memory and anxiety-like behavior.

Neonatal ionizing radiation exposure has been shown to induce a cerebellar cytoarchitecture disarrangement. Since cerebellar abnormalities have been linked to an impairment of behavioral functions, the aim of the present work was to investigate whether exposure of developing rats to ionizing radiations can produce behavioral deficits in the adult. Male Wistar rats were X-irradiated with 5Gy within 48h after birth and were tested in a radial maze and in an open field at 30 and 90 days post irradiation. Irradiated rats showed significative changes in spatial, exploratory, and procedural parameters in the radial maze, as well as a significative decrease in anxiety-like behavior, assessed in the open field. These results suggest that ionizing radiations can induce long-lasting spatial memory and anxiety-related changes. A relationship with radiation-induced cerebellar cytoarchitecture abnormalities supports the hypothesis that cerebellar integrity seems to be critical to achieve spatial performance and emotional behavior establishment.

Epilepsia partialis continua of the abdominal muscles: a detailed electrophysiological study of a case.

We describe the clinical and electrophysiological features of an elderly woman presenting with persistent clonic twitching of the abdominal muscles that were considered to represent a rare manifestation of epilepsia partialis continua due to a metastatic cortical lesion.

GM1 ganglioside treatment protects against long-term neurotoxic effects of neonatal X-irradiation on cerebellar cortex cytoarchitecture and motor function.

Exposure of neonatal rats to a 5 Gy dose of X-irradiation induces permanent abnormalities in cerebellar cortex cytoarchitecture (disarrangement of Purkinje cells, reduction of thickness of granular cortex) and neurochemistry (late increase in noradrenaline levels), and motor function (ataxic gait). The neuroprotective effects of gangliosides have been demonstrated using a variety of CNS injuries, including mechanical, electrolytic, neurotoxic, ischemic, and surgical lesions. Here, we evaluated whether systemically administered GM1 ganglioside protects against the long-term CNS abnormalities induced by a single exposure to ionizing radiation in the early post-natal period. Thus, neonatal rats were exposed to 5 Gy X-irradiation, and subcutaneously injected with one dose (30 mg/kg weight) of GM1 on h after exposure followed by three daily doses. Both at post-natal days 30 and 90, gait and cerebellar cytoarchitecture in X-irradiated rats were significantly impaired when compared to age-matched controls. By contrast, both at post-natal days 30 and 90, gait in X-irradiated rats that were treated with GM1 was not significantly different from that in non-irradiated animals. Furthermore, at post-natal day 90, cerebellar cytoarchitecture was still well preserved in GM1-treated, X-irradiated animals. GM1 failed to modify the radiation-induced increase in cerebellar noradrenaline levels. Present data indicate that exogenous GM1, repeatedly administered after neonatal X-irradiation, produces a long-term radioprotection, demonstrated at both cytoarchitectural and motor levels.

Effects of prenatal exposure to low dose ionizing radiation on the development of the cerebellar cortex in the rat.

The effects of maternal exposure to a single dose of whole body irradiation (0.5 Gy) on gestational days (GD) 17, 18, 19, or 20 on the development of the cerebellar cortex was examined in the offspring of Sprague Dawley rats at 21 and 28 days postnatally. No gross cerebellar anomalies were observed in the irradiated animals. However, compared to control animals, rat irradiated on each of GD-17, 18, 19 and 20 showed a significantly higher incidence (p < 0.05) of circumscribed cerebellar lesions (CL) distributed in the inner granular layer of the anterior and posterior lobes. These lesions were characterized by a loss of granule cells and atrophied and/or reduced number of Purkinje cells. In 21 days old rats, irradiation on GD-17 resulted in more CL anteriorly (75%) and in the vermis whereas on GD-20, the CL predominated posteriorly (100%) and in the lateral hemispheres. In 28 day old rats, following irradiation on each of GD-17 and GD-20, there was an equal distribution of CL in both the anterior and posterior lobes. However, with irradiation on both GD-17 and GD-20, these CL occurred more frequently in the lateral hemispheres of the anterior lobe, whereas in the posterior lobe they predominated in the vermis. These results suggest that a direct relationship exists between the proliferation, migration, development, and maturation of granule cells and their induction by Purkinje cells. The findings also support the view that both cell death and the regulation of granule cells by Purkinje cells maximize the effective development and organization of the cerebellum.

Purkinje and granule cells distribution in the cerebellum of the rat following prenatal exposure to low dose ionizing radiation.

The effects of maternal exposure to a single dose of whole body irradiation (0.5 Gy) on gestational days (GD) 17, 18, 19, or 20 on the number of Purkinje and granule cells in the pyramis of the cerebellar cortex was examined in the offspring of Sprague Dawley rats at 21 and 28 days postnatally. The laterolateral distribution of both granule and Purkinje cells in the pyramis were significantly reduced (p < 0.001) from controls in rats irradiated on each of GD-17, 18, 19 and 20. There was a greater deficit in granule cell number with irradiation on GD-20 than on GD17 (p < 0.05). Purkinje cells were reduced in number with irradiation on GD-17 and GD-20; however, the decrease did not correspond to the degree of reduction in the number of granule cells. There was a greater reduction of both granule and Purkinje cells in the vermis with irradiation on GD-17, whereas on GD-20, both granule (p < 0.05) and Purkinje cells (p < 0.001) were more reduced in the lateral hemispheres. The GC/PC ratio was smaller in rats irradiated on GD-20 than on GD-17. The GC/PC ratio between the irradiated animals and the controls were relatively similar. The findings show that irradiation does not affect the population of granule cells directly, but rather indirectly. The reduction in the number of granule cells could be an indirect consequence of reduced critical interaction with Purkinje cells. These results suggest that a direct relationship exists between the proliferation, migration, development, and maturation of granule cells and their induction by Purkinje cells.

Noradrenergic innervation of ectopic granule cells following low-level X-irradiation.

The distribution pattern of the noradrenergic system within the cerebellar cortex following low-level X-irradiation was studied using immunocytochemistry. Following one X-irradiation exposure on postnatal day 1, the laminar distribution of tyrosine hydroxylase-like immunoreactive (THIR) fibers was similar to controls at postnatal day 30, but the orientation of the fibers in the molecular layer (ML) was slightly changed. Successive daily doses, however, produced alterations in both the pattern and concentration of THIR fibers within the ML of the cerebellar cortex. In addition, THIR fibers were found among ectopic cell clusters within the ML. This relationship suggests a potential role for the noradrenergic system in the development and/or maintenance of the ectopic cell clusters.

Gamma-radiation produces abnormal Bergmann fibers and ectopic granule cells in mouse cerebellar cortex.

Morphological changes in Bergmann glial fibers in the developing cerebellar cortex produced by exposure to gamma-rays were investigated in association with ectopic granule cells. Six-day-old mice that had been exposed to 3 Gy of gamma-radiation were killed 6 hours after exposure or at 7 through 30 days of age. Their cerebella were examined histologically and immunohistochemically for glial fibrillary acidic protein in Bergmann fibers. Extensive cell death took place in the external granular layer (EGL) of the cerebellum from 6 through 24 hours after exposure. This led to the thinning of the EGL and a decrease in the number of migrating cells in the molecular layer. The number of Bergmann cells was not decreased, but the fibers in the molecular layer were distorted; whereas, in the control these fibers were straight and perpendicular to the pial surface. The EGL began to recover 2 days after exposure, and abnormally oriented migrating cells were seen. At 17 days of age, some cell clustering was observed in the molecular layer of the irradiated cerebellum. Distortion of the Bergmann fibers was marked in regions where ectopic granule cells appeared at 30 days of age. These findings suggest that the distortion of Bergmann fibers leads to the production of ectopic granule cells after exposure to gamma-radiation.

Radiation-induced DNA strand breaks and cell pycnosis in the developing rat cerebellum.

DNA strand breaks and cell pycnosis induced by 60Co gamma radiation were studied in the developing rat cerebellum. Rats 2, 5 or 12 days old were irradiated and the repair of DNA strand breaks was studied at various intervals up to seven hours. DNA strand breaks were repaired in 30 min and post-repair DNA degradation was observed about 90 min after irradiation in 12 day old rats and some time later in the younger ones. The pycnotic activity in the external granular layer of the cerebellar cortex seen in histological preparations developed in a similar way, the older rats showing earlier signs of cell pycnosis and a faster degradation of DNA. A correspondence was found between DNA degradation and cell pycnosis.

Late ultrastructural changes in neuronal mitochondria after lonizing radiation of the brain.

Brain tissue was examined for morphological changes at 12 and 16 months after focal irradiation of the brain in female mice. Irradiation was performed with deuteron beams derived from the 60-inch Brookhaven cyclotron at a rate of 1925 rad second -minus 1 though an anti-Bragg device which produced uniform exposure. Experimental animals received a dose of 10,000 rad, covering a 9 by 5 mm area over the skull and extending into the brain from a depth of about 2 mm. An additional group of animals served as sham-irradiated controls. Histological studies revealed extensive cell loss, vacuolation, and prominent vascular changes in irradiated regions of the brain at 16 months post-irradiation. Ultrastructural examination of brain tissue at 12 and 16 months after irradiation revealed the presence of unusual elongated mitochondria with parallel arrays of cristae. Altered mitochondria were more prevalent at the longer post-irradiation interval.