6-HYDROXYDOPAMINE LESION OF RAT NIGROSTRIATAL DOPAMINERGIC-NEURONS DIFFERENTIALLY AFFECTS NICOTINIC ACETYLCHOLINE-RECEPTOR SUBUNIT MESSENGER-RNA EXPRESSION

Nicotinic acetylcholine receptor (nAChR) subunit mRNA expression in th e rat substantia nigra (SN) was assayed by semiquantitative RT-PCR fol lowing 6-hydroxydopamine (6-OHDA) lesion of nigrostriatal dopaminergic neurons. Six months after unilateral injection of 6-OHDA or saline in to the SN, total RNA was isolated from ipsilateral and contralateral t issue samples. RT-PCR amplifications were performed with template titr ation using primers specific for sequences encoding 1. nAChR alpha 2-a lpha 7 and beta 2-beta 4 subunits 2. Glutamic acid decarboxylase 3. Gl yceraldehyde 3-phosphate dehydrogenase for normalization of template m ass. PCR products specific for alpha 3, alpha 4, alpha 5, alpha 6, alp ha 7, beta 2, beta 3, and glutamic acid decarboxylase were detected in the reactions containing SN RNA. This is the first evidence that alph a 7 may be expressed in the SN. alpha 2 and beta 4 PCR products were n ot detected in SN reactions, although they were observed in hippocampu s and thalamus control reactions. A comparison of ipsilateral and cont ralateral SN RT-PCR reaction products showed substantial decreases in alpha 5, alpha 6, and beta 3 product yields following 6-OHDA, but not sham treatment. Neither the SN of sham-lesioned rats nor the thalamus of 6-OHDA-lesioned rats yielded similar results, indicating that the e ffects observed in 6-OHDA-treated SN were not caused by local mechanic al damage or a nonspecific response, respectively. Effects of 6-OHDA t reatment on alpha 3, alpha 4, alpha 7, beta 2, or glutamic acid decarb oxylase product yields from SN samples were small or undetectable. The results suggest that alpha 5, alpha 6, and beta 3 subunit-encoding mR NAs are expressed at substantially higher levels in dopaminergic than in nondopaminergic cell bodies in the SN.