l']ur,,7~ean Journal of Pharmacology - Molecular Pha~w~acolt~w Sectiotl, 225 (1992) 143- ! 5(I © 1992 Elsevier Science Pub!ishers B.V. All tighls reserved 0022-4106/92/$05.00
143
EJPMOL 90263
Ontogeny of dopamine D 2 receptor mRNA in rat brain Latit K. Srivaotava, Michel A. M o r e n c y and R a m K. Mishra Departments of P~'chiatry and Biomedical Sciences. Facuhy of lleahh Sciences, McMaster Unit'ersity, ttamihon, Ontario L8N 3Z5, Canada Received 21 August 1991, revised MS recmved 30 October 1991. accepted 5 November 1991
The postnatal development of rat brain dopamine D 2 receptor gene expression was investigated in animals 1 day to 1 year old. The level of expression of the striatal De mRNA was appreciable at birth (day 1), steadily increased to a maximum at day 28, and showed declines at ages 6 months and one year. The mRNA development profile was similar to that of [SH]spiroperidol binding in striatal membranes except that there was a lack of correlation between mRNA levels and [3H]spiroperidol binding during the early developmental periods. For example, although the mRNA expression at day 1 is about 75% of the 28-day value, the corresponding level of [3H]spiropcridol binding is only 15g~ of the value observed at day 28. Polymerase chain reaction (PCR) analysis of alternatively spliced ~orms of D 2 receptor mRNA showed that the developmental expression of the two isoforms proceeded in parallel as the ratio of D2t and D2s mRNAs remained more or less constant in different age group of rats. In situ hybridization revealed a differential developmental profile of D, mRNA for major dopaminergic regions of rat brain such as caudate putamen, nucleus accumben:;, olfactory tubercle and substantia nigra. D o p a m i n e D 2 receptor; mRNA; Brain: Development
I. Introduction
Ontogeny studies of both dopamine D t and D e receptors in rodent brains show that the density of receptors is relatively low at birth and increases at a steady rate for the first 3-4 weeks postnatatly (Pardo et al., 1977; Bruinink et al., 1983; Hartley and Seeman, 1983; Murrin and Zeng, 1986; Zeng et al., 1988; Sales et al., 1989; Rao et al., 1991), A significant decrease in striatal dopamine D 2 receptor density has been noted during the aging process in both rodents and humans (O'Boyle and Waddington, !984; Henry et al., 1986; Hyttel, 1987; Rinne et al., 1990). Investigations into the mechanism of such changes are necessary in order to understand the declines of dopamine-related psychomotor performance in senescence. It has been proposed that the age-related decline in dopamine D, receptor may be due to a decrease in net biosynthesis of the receptor (Henry et al., 1987). Missale et al. (1987) have provided evidence that the decrease in D 2 receptor binding in rat striatum during aging may re-
Correspondence to: Dr. Ram K. Mishra, Departments of Psychiat~" and Biomedical Sciences. Faculty of ttealth Sciences, Room 4N52~ McMaster University, 12(R) Main Street East. Hamilton, Ontario L8N 3Z5, Canada. Tel. (416) 525-9140. exts, 2396/2467; Fax (41fi) 521-{}048.
flect a selective loss of one sub-populatio~ of the receptor that may not be coupled to adenylate cyclase. Consistent with the hypothesis of a net decline in D~ receptor biosynthesis during aging, a recent report by Mesco et at. (1991) shows that the level of D 2 receptor mRNA in the striatum of aged rats is only half of that seen in the adult animals. The cDNA and gene for rat and human dopamine D 2 receptor have recently been cloned and sequenced ~'Bunzow et al., 1988; Grandy et al., 1989; Selbie et al., 1~89). In both species, two isoforms of the receptor, resulting from alternative RNA splicing, have been detected (Dal Toso et al.. 1989; Giros et al., 1989; Grandy et al., 1989; Monsma et al., 1989; Selbie et al., 1989; Chio et al., 1990). One isoform contains 415 amino acids and is termed D2s, D2B, o r D2o15 ) while the other isoform termed Dec, D, A or D~
143
EJPMOL 90263
Ontogeny of dopamine D 2 receptor mRNA in rat brain Latit K. Srivaotava, Michel A. M o r e n c y and R a m K. Mishra Departments of P~'chiatry and Biomedical Sciences. Facuhy of lleahh Sciences, McMaster Unit'ersity, ttamihon, Ontario L8N 3Z5, Canada Received 21 August 1991, revised MS recmved 30 October 1991. accepted 5 November 1991
The postnatal development of rat brain dopamine D 2 receptor gene expression was investigated in animals 1 day to 1 year old. The level of expression of the striatal De mRNA was appreciable at birth (day 1), steadily increased to a maximum at day 28, and showed declines at ages 6 months and one year. The mRNA development profile was similar to that of [SH]spiroperidol binding in striatal membranes except that there was a lack of correlation between mRNA levels and [3H]spiroperidol binding during the early developmental periods. For example, although the mRNA expression at day 1 is about 75% of the 28-day value, the corresponding level of [3H]spiropcridol binding is only 15g~ of the value observed at day 28. Polymerase chain reaction (PCR) analysis of alternatively spliced ~orms of D 2 receptor mRNA showed that the developmental expression of the two isoforms proceeded in parallel as the ratio of D2t and D2s mRNAs remained more or less constant in different age group of rats. In situ hybridization revealed a differential developmental profile of D, mRNA for major dopaminergic regions of rat brain such as caudate putamen, nucleus accumben:;, olfactory tubercle and substantia nigra. D o p a m i n e D 2 receptor; mRNA; Brain: Development
I. Introduction
Ontogeny studies of both dopamine D t and D e receptors in rodent brains show that the density of receptors is relatively low at birth and increases at a steady rate for the first 3-4 weeks postnatatly (Pardo et al., 1977; Bruinink et al., 1983; Hartley and Seeman, 1983; Murrin and Zeng, 1986; Zeng et al., 1988; Sales et al., 1989; Rao et al., 1991), A significant decrease in striatal dopamine D 2 receptor density has been noted during the aging process in both rodents and humans (O'Boyle and Waddington, !984; Henry et al., 1986; Hyttel, 1987; Rinne et al., 1990). Investigations into the mechanism of such changes are necessary in order to understand the declines of dopamine-related psychomotor performance in senescence. It has been proposed that the age-related decline in dopamine D, receptor may be due to a decrease in net biosynthesis of the receptor (Henry et al., 1987). Missale et al. (1987) have provided evidence that the decrease in D 2 receptor binding in rat striatum during aging may re-
Correspondence to: Dr. Ram K. Mishra, Departments of Psychiat~" and Biomedical Sciences. Faculty of ttealth Sciences, Room 4N52~ McMaster University, 12(R) Main Street East. Hamilton, Ontario L8N 3Z5, Canada. Tel. (416) 525-9140. exts, 2396/2467; Fax (41fi) 521-{}048.
flect a selective loss of one sub-populatio~ of the receptor that may not be coupled to adenylate cyclase. Consistent with the hypothesis of a net decline in D~ receptor biosynthesis during aging, a recent report by Mesco et at. (1991) shows that the level of D 2 receptor mRNA in the striatum of aged rats is only half of that seen in the adult animals. The cDNA and gene for rat and human dopamine D 2 receptor have recently been cloned and sequenced ~'Bunzow et al., 1988; Grandy et al., 1989; Selbie et al., 1~89). In both species, two isoforms of the receptor, resulting from alternative RNA splicing, have been detected (Dal Toso et al.. 1989; Giros et al., 1989; Grandy et al., 1989; Monsma et al., 1989; Selbie et al., 1989; Chio et al., 1990). One isoform contains 415 amino acids and is termed D2s, D2B, o r D2o15 ) while the other isoform termed Dec, D, A or D~
