| Research Abstract |
The brains of rats injected intravenously with ^<65>ZnCl_2 or ^<54>MnC_2 were subjected to high-resolution autoradiography. The distribution of ^<65>Zn and ^<54>Mn in each brain region gradually decreased from 6 days to 42 days for ^<65>Zn and form 15 days to 60 days for 54 Mn after the injection. The biological half-lives of Zn in each region studied were in the range of 16-43 days ; the longest was observed in the amygdaloid nuclei. The regions where the long biological half-life was observed were consistent with the ones with the high density of Zn-containing neuton terminals reported previously. The biological half-lives of Mn in each region determined were 51-74 days ; the longest were those in the hypothalamic nuclei and thalamus.
To study zinc (Zn) mobility in the rat olfactory tract, brain distribution of ^<65>Zn after injection into the olfactory bulb or amygdaloid nuclei was analyzed by autoradiography. Twenty-four h after ^<65>Zn injection into the olfactory bulb, ^<65>Zn was
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distributed in the ipsilateral piriform cortex, amygdaloid nuclei and the anterior commissure. Moreover, in the case of injection of a higher level of ^<65>Zn into the olfactory bulb, ^<65>Zn was distributed in the ipsilateral entorhinal cortex in addition to the above regions. Twenty-four h after ^<65>Zn injecjtion into the amygdaloid nuclei, ^<65>Zn was distributed in the ipsilateral piriform and entorhinal cortex. These results suggest that Zn is intraneuronally transported along the olfactory tract. Zn may be taken up by the piriform neurons after release from the secondary olfactory neuron terminals and transported to the entorhinal area.
^<65>Zn was injected into the striatum or substantia nigra of rats to see the mobility of intracerebral Zn. In the case of intrastriatal injection, ^<65>Zn was densely distributed in the medial forebrain bundle (MFB) and substantia nigra. In the case of intranigral injection, ^<65>Zn was densely distributed in the MFB and also in the striatum and globus pallidus. On unilateral colchicine injection into the MFB,^<65>Zn distribution in the ipsilateral substantia nigra decreased significantly compared to that of the contralateral one after ^<65>Zn injection into the striatum. These results suggest the presence of axonal transport of Zn in pathway of g-amino butyric acid (GABA)-ergic striato-nigra fibers. Moreover, the ^<65>Zn distribution data 1 day after both injections indicated that its distributed regions were those with the GABAergic systems. Less
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