(Scale pub:aandb, 25 m;c, 8 m;d, 400 m;e, 25 m;f, 80 m;gandi, 67 m;handj, 10 m.) For double-labeling electron microscopic level analysis, Vibratome sections (40 m) were incubated in a mixture containing either D2S or D2L antibody and antisera against dopaminergic markers such as TH or dopamine transporter (DAT; 1:500, Chemicon). in dopaminergic cell body and axons strongly suggests that this isoform is GSK2593074A the likely dopamine autoreceptor, whereas the D2 very long isoform is definitely primarily a postsynaptic receptor. Among all the neurotransmitter receptors cloned to date, the D2 subtype of dopamine receptors has been the one most closely linked to the positive symptoms of schizophrenia (1,2) and often implicated in extrapyramidal side effects (3,4). Neuroanatomical (5,6) and physiological (7,8) studies indicate that this receptor offers both autoreceptor and postsynaptic functions. Further, recent evidence of loss of autoreceptor function in D2-deficient mice (8) but sparing of this function in D3 mutant mice (9) strongly suggests that the GSK2593074A D2 subtype is the only autoreceptor within the dopamine system. However, the D2 receptor is present in two isoforms (10,11), and it is not known if both isoforms contribute to autoreceptor function. With the use of recently developed subtype-specific antibodies to dopamine D2 short (D2S) and D2 very long (D2L) isoforms, we have found prevalent labeling of the D2S isoform in the cell body and axons of mind stem dopamine neurons, suggesting that this isoform is the autoreceptor of the dopamine system. == METHODS == == Preparation of Antibodies. == The D2S peptide TPLKDAAR and D2L peptide SNGSFPVNRRRM related to residues 238245 and 259270 (10,11), respectively, were derived from the third cytoplasmic loop of Mouse Monoclonal to S tag the receptor. The D2S peptide was arranged by adopting four amino acids from each part of the insertion site to differentiate between D2S and D2L isoforms. A similar procedure offers previously GSK2593074A been used for the preparation of antibodies to -aminobutyric acid (GABA) receptors (12). The peptides were coupled to keyhole limpet hemocyanin (KLH) protein. PeptideKLH conjugate (100 g) emulsified in total Freunds adjuvant was injected into rabbits for antibody development. Affinity purification of the antisera was as explained elsewhere (12). In brief, peptide (5 mg) was coupled to 1 1 g of triggered thiopropyl-Sepharose 6B (Pharmacia LKB). Phosphate-buffered saline (PBS) diluted antiserum (1:5) was circulated through the column. After washing with PBS, the antibody was eluted with glycineHCl, pH 2.3, and dialyzed against PBS. == Membrane Preparation. == Adult rhesus monkey (Macaca mulatta) brains were used for the preparation of cells membranes as explained earlier (13). Briefly, brain tissues were homogenized with 10% sucrose in TrisHCl, pH 7.4, and centrifuged at 3,000 rpm inside a Sorvall for 5 min. The supernatant was centrifuged at 35,000 rpm for 1 h in Beckman ultracentrifuge, and the resultant pellet was washed three times in 50 mM TrisHCl, pH 7.4. The membranes were suspended, and their protein concentration was determined by the Lowry method. == Immunoblots. == Striatal and substantia nigra membrane proteins (17 g per lane) and recombinant membranes of Sf9 cells (BioSignal) expressing numerous dopamine receptors (2 g per lane) were separated by SDS/10% PAGE and transblotted. Nitrocellulose pieces comprising cells membranes were incubated with 5 g/ml antibodies to D2S and D2L, followed by incubation with anti-rabbit IgG (1:200, Sigma) and peroxidaseantiperoxidase (1:100, Sigma) and developed with 0.05% diaminobenzidine (Fig.1). The nitrocellulose pieces comprising recombinant cell membranes were incubated with horseradish peroxidase-conjugated anti-rabbit IgG (1:2000, Amersham), and bands were visualized by using an ECL kit (Amersham; Fig.1aandb). Settings included preincubation with 25 g/ml respective antigen peptide. == Number 1. == Immonoblots of monkey mind cells and crude membranes of recombinant Sf9 cell lines expressing dopaminergic human being D1, D2S, D2L, D3rat, D4.2, and D5 receptors are shown with D2S (a) and D2L (b) antibodies. Both antibodies immunoreacted.