344 Bram Research, 362 (1986) 344-349 Elsevier BRE 11357 In Vivo Measurement of Spontaneous Release and Metabolism of Dopamine from Intrastriatal Nigral Grafts Using Intracerebral Dialysis T ZETI'ERSTROM l, P BRUNDIN2, F H GAGE2, T. SHARP l, O ISACSON2, S B. DUNNETT 3, U UNGERSTEDT l and A BJORKLUND 2 1Departmentof Pharmacology, Karohnska Institute, Stockholm, 2Departmentof Histology, Umverstty of Lund, (Sweden) and 3Department of Experimental Psychology, Umversttyof Cambridge (U K ) (Accepted May 7th, 1985) Key words in vivo dmlysls- - transplantauon- - neostrlatum - - dopamlne - - release Spontaneous release and metabohsm of dopamme (DA) from mtrastnatal grafts of fetal mesencephahc DA neurons was measured by mtracerebral dialysis Mesencephahc DA cell suspensions were implanted into the head of the caudate-putamen in rats with undat- eral 6-hydroxydopamlne (6-OHDA) lesions of the mesostrlatal DA pathway. Four months later, when tests for amphetamine-induced turning behavlour showed that the grafts had become functional, loops of &alysis tubing were implanted into the striatum on the graft- ed side and the contralateral non-les~onedside of the grafted rats, and in a similar position in the denervated caudate-putamen of 6- OHDA lesioned control rats Dialysis perfusates collected from the 6-OHDA lesioned stnata showed a reduction of about 95-98% in DA and its metabohtes 3,4-dihydroxyphenylacetlc acid (DOPAC) and homovandhc aod (HVA) In the grafted animals these levels had recovered to about 40% of control for DA and to 12-16% of control for HVA and DOPAC In addition, the serotonm metabohte 5-hydroxymdoleacetlc acid (5-HIAA) was increased in the grafted striata compared to both the lesioned and non-lesioned controls Amphetamine had little or no effect on DA release in the 6-OHDA lesioned rats, but caused a marked increase in DA release in the grafted rats, this response being proportional to that seen in intact stnata Sincethe subsequent h~stochemicalanalys~s showed that the dialysis probe had been located in the transplant-remnervated part of the caudate-putamen, the results provide addmonal evidence that the grafted DA neurons exert their functional effects through a continuous active transmitter release from their newly-estab- hshed terminals m the remnervated host target INTRODUCTION Fetal mesencephalic dopamine (DA)-contamlng neurons grafted to the dopaminergically denervated neostrtatum of adult recipient rats are capable of re- establishing a new DA innervation of the adjacent host neostnatum 2.3,11 and forming ultrastructurally normal synapses with the previously denervated neo- strlatal neurons 12. Such grafts have also been found to ameliorate a range of motor and sensorimotory functional deficits associated with unilateral or bilat- eral destruction of the mesostriatal DA pathway2-4, 6-11,16. Since the compensatory behavioural effects of mgral grafts are seen not only after pharmacological activation, but also m the drug-free behaving animal, it appears that the grafted DA neurons are sponta- neously active In their new location within the host bram Direct measurements of spontaneous DA release from the new 'nigro-striatal' connections established by intrastriatal nigral grafts have, however, so far not been performed. In the present study we have made use of the recently mtroduced intracerebral dialysis technique 19,20,22 for this purpose. The experiments involved collecting peffusates from a loop of dialysis tubing implanted into the transplant reinnervated re- gion of the grafted host striatum, followed by analysis of DA, its acid metabolites 3,4-dihydroxyphenyla- cetic acid (DOPAC) and homovanillic acid (HVA), and the serotonin metabolite 5-hydroxymdole acetic acid (5-HIAA) in the perfusates using high-perform- ance liqmd chromatography (HPLC) with electro- chemical detection The results show that graft-de- pendent DA release and metabohsm can readily be monitored with the dialysis method, and they provide additional evidence that the grafted DA neurons re- Correspondence A Bjorklund, Department of Histology, Btskopsgatan 5, S-223 62 Lund, Sweden 0006-8993/86/$03 50 © 1986 Elsevier Science Pubhshers B V (Biomedical Dwtslon)