Grafted Dopamine Neurons Research Articles

Chapter 55 Matrigel enhances survival and integration of grafted dopamine neurons into the striatum

Publisher Summary Matrigel is a biopolymer of natural constituents containing large proteins, which have been shown to promote neurite outgrowth in culture. This chapter aims to enhance the survival and promote outgrowth and integration of fetal dopamine neurons transplanted into the striatum of unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rodents immediately after cavitation. The chapter also describes the effects of Matrigel on transplantation of fetal substantia nigra into the striatum. Innervation of blood vessels into the transplanted tissue appeared to be enhanced by the Matrigel. The effects of Matrigel may be because of a number of factors, such as Matrigel contains a large percentage of laminin and type 4 collagens, which are important structural requirements for attachment of cells and neurite outgrowth; or Matrigel may be promoting the survival and outgrowth of the fetal neurons by stimulating growth factors from the endogeneous striatal tissue. The positive effects of Matrigel may be related to promoting ingrowth of blood vessels and thereby increase the circulation in the transplanted region. However, the fact that substance P-positive innervation of the transplanted tissue took the form of woolly fibers, strongly suggests that these fibers are making the appropriate synaptic contacts.

Synaptic investment of striatal cellular domains by grafted dopamine neurons in weaver mutant mice.

Synaptic investment of striatal cellular domains by grafted dopamine neurons in weaver mutant mice.

Dopamine neuron transplants: Electrophysiological unit activity of intrastriatal nigral grafts in freely moving cats

Fetal transplants of substantia nigra dopamine (DA)-containing neurons into the caudate nucleus in cats produced functional synaptic connections, as measured by behavioral analysis. Electrophysiological activity of single units from the intrastriatal nigral grafts revealed that these neurons displayed some of the characteristic electrophysiological parameters of DA neurons, i.e., long duration action potentials and tri-phasic waveform. However, these neurons discharged at a faster rate and never displayed the characteristic decremental burst pattern seen in intact, non-grafted animals. These data are the first electrophysiological recordings of grafted DA neurons in freely moving animals.

In vivo measurement of spontaneous release and metabolism of dopamine from intrastriatal nigral grafts using intracerebral dialysis

Spontaneous release and metabolism of dopamine (DA) from intrastriatal grafts of fetal mesencephalic DA neurons was measured by intracerebral dialysis. Mesencephalic DA cell suspensions were implanted into the head of the caudate-putamen in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the mesostriatal DA pathway. Four months later, when tests for amphetamine-induced turning behaviour showed that the grafts had become functional, loops of dialysis tubing were implanted into the striatum on the grafted side and the contralateral non-lesioned side 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 striata showed a reduction of about 95–98% in DA and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (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 serotonin metabolite 5-hydroxyindoleacetic 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 striata. Since the subsequent histochemical analysis showed that the dialysis probe had been located in the transplant-reinnervated part of the caudate-putamen, the results provide additional evidence that the grafted DA neurons exert their functional effects through a continuous active transmitter release from their newly-established terminals in the reinnervated host target.

Intrastriatal grafting of dopamine-containing neuronal cell suspensions: Effects of mixing with target or non-target cells

The effects of target and non-target cells on the growth and function of intrastriatal grafts of mesencephalic dopamine neurons have been studied in rats with unilateral 6-hydroxydopamine-induced lesions of the nigrostriatal dopamine pathway. Cell suspensions of ventral mesencephalon from 14–15-day-old rat fetuses (rich in developing dopamine neurons) were either grafted alone or grafted after mixing with equivalent numbers of cells obtained from the striatum (a major dopamine target area) or spinal cord (a non-target area for the mesencephalic dopamine neurons). The combined mesencephalic and striatal grafts gave rise to a greater area of dense innervation in the host caudate-putamen than grafts of mesencephalic cells alone or grafts of mesencephalic cells mixed with spinal cord cells. The number of surviving catecholamine-containing neurons did not differ significantly in the different types of grafts. In addition, there was an altered outgrowth pattern in the combined mesencephalic-striatal grafts consisting of small round islands of intensely fluorescent catecholamine-containing fibres, often in close association with the grafted dopamine neurons. In a subsequent biochemical study it was found that combined mesencephalic-striatal grafts exhibited dopamine levels and turnover that did not differ from grafts containing mesencephalic cells only. The mesencephalic-striatal cografts showed a trend toward enhanced behavioural effect, in terms of greater reduction in amphetamine-induced rotation asymmetry, when compared to other graft groups. It is suggested that the addition of embryonic striatal target cells can exert stimulatory effects on morphological development, and possibly functional parameters, of fetal dopamine cells also in vivo after intrastriatal grafting. However, the results differ in principle from those obtained in analogous in vitro studies, possibly due to the presence of adult host striatal target cells in all the groups in the present experiments.

Regeneration of monoaminergic and cholinergic neurons in the mammalian central nervous system

Regeneration of monoaminergic and cholinergic neurons in the mammalian central nervous system