Complex sentence: So, since 1966, he participated in TV series episodes such as Laredo (1966) and Marcus Welby, M.D. (1968), after of which, he left also the American TV.
Split into simpler sentences: So, since 1966, he participated in TV series episodes such as Laredo (1966) and Marcus Welby, M.D. (1968). After of this TV series, he left also the American TV.