DIGITAL IMAGING OF HEMATOPORPHYRIN DERIVATIVE DISTRIBUTION IN RAT-BRAIN FOLLOWING INTRACEREBRAL ADMINISTRATION

The distribution of intracerebrally injected HPD in rat brain was anal ysed by means of a digital imaging system. A technique based on light absorption and optical densitometry was applied for measuring and anal ysing relative HPD concentrations. According to our knowledge there ar e no earlier reports on this digital imaging technique for measuring t issue concentrations of HPD. The HPD distribution was analysed at diff erent intervals after local administration in the caudate nucleus-puta men, ranging from 0 h to 5 days. HPD was distributed in a complex patt ern. The observed distribution pattern was partly determined by the lo cal anatomical and cellular structures of the caudate nucleus-putamen, which were more or less outlined by HPD staining. Furthermore, a conc entration gradient from the centre to the periphery of the HPD zone wa s observed. Both factors contributed to the distribution pattern. The ratio of the HPD concentration in grey and white matter increased at l onger intervals, indicating more efficient removal of HPD in white mat ter compared with grey matter.