ergoline and cresyl-violet

The cellular distribution of tyrosine hydroxylase (TH) and TH mRNA in the rat substantia nigra (SN) was investigated using immunohistochemistry (IMHC) and non-radioactive in situ hybridization histochemistry (ISH), respectively. Number and density of both TH immunoreactive and TH cRNA labeled cells were increased in the pars reticulata of the substantia nigra (SNr) 8 h after single administration of a dopamine antagonist haloperidol. At the same time number and density of TH positive cells remained unchanged in a ventro-medial, dorso-medial or lateral part of the pars compacta (SNc) and in the pars lateralis (SNl) of the substantia nigra. A D2 receptor-specific agonist, quinpirole, was without effect on either ISH or IMHC in any of these areas, including the SNr. These results reveal the existence of a population of TH-negative neurons in the SNr, in which TH gene-expression can be activated through a dopamine receptor-mediated mechanism, leading to detectable levels of both TH and TH mRNA. Furthermore they suggest that TH gene-expression in these neurons normally is inhibited by dopamine released from somata and dendrites in the SNr.

Topics: Animals; Benzoxazines; Dopamine Agents; Dopamine D2 Receptor Antagonists; Enzyme Activation; Ergolines; Gene Expression; Haloperidol; Immunohistochemistry; In Situ Hybridization; Male; Oxazines; Quinpirole; Rats; Rats, Wistar; Receptors, Dopamine D1; Receptors, Dopamine D2; RNA, Messenger; Substantia Nigra; Tyrosine 3-Monooxygenase