We report for the first time on the production and characterization of antibodies against a naturally occurring tetrahydroisoquinoline, namely salsolidine (6,7-dimethoxy-1-methyl-1,2,3,4-tetrahydroisoquinoline). 2. Immunogen synthesis was carried out by coupling the hapten salsolidine to bovine serum albumin (BSA) as carrier protein on the basis of reductive amination. 3. By immunization of rabbits with salsolidine-BSA conjugate antisalsolidine antibodies were produced. 4. At a final dilution of 1:1700 the highest-titre antiserum bound 35% of 0.21 pmol [3H]salsolidine. This antiserum was used to develop a radioimmunoassay for salsolidine. 5. Cross-reactivity studies revealed a high specificity of the antiserum to the hapten. 6. The antibodies had a high affinity to salsolidine (Ka = 1.5 x 10(9) M-1). 7. Standard curves covered a measuring range of 0.5-70 pmol/tube and the detection limit was found to be 0.27 pmol/tube.
