Studies of physiology and the morphology of the cat LGN following proton irradiation.
OBJECTIVE
We have examined the effects of proton irradiation on the histologic and receptive field properties of thalamic relay cells in the cat visual system. The cat lateral geniculate nucleus (LGN) is a large structure with well-defined anatomical boundaries, and well-described afferent, efferent, and receptive field properties.


METHODS
A 1.0-mm proton microbeam was used on the cat LGN to determine short-term (3 months) and long-term (9 months) receptive field effects of irradiation on LGN relay cells. The doses used were 16-, 40-, and 60-gray (Gy).


RESULTS
Following irradiation, abnormalities in receptive field organization were found in 40- and 60-Gy short-term animals, and in all of the long-term animals. The abnormalities included "silent" areas of the LGN where a visual response could not be evoked and other regions that had unusually large or small compound receptive fields. Histologic analysis failed to identify cellular necrosis or vascular damage in the irradiated LGN, but revealed a disruption in retinal afferents to areas of the LGN.


CONCLUSIONS
These results indicate that microbeam proton irradiation can disrupt cellular function in the absence of obvious cellular necrosis. Moreover, the area and extent of this disruption increased with time, having larger affect with longer post-irradiation periods.
Reder
C S
CS
Department of Pediatrics, Loma Linda University, Loma Linda, CA 92350, USA. mkirby@som.llu.edu
Moyers
M F
MF
Lau
D
D
Kirby
M A
MA
D000818:Animals; D002415:Cats; D004307:Dose-Response Relationship, Radiation; D005829:Geniculate Bodies / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects*; D009475:Neurons, Afferent / Q000502:physiology / Q000528:radiation effects; D011522:Protons; D011853:Radiobiology; D012160:Retina / Q000502:physiology / Q000528:radiation effects; D013997:Time Factors
D011522:Protons