In search for a new lead of non-imidazole histamine H3-receptor antagonists, a series of 1 [(2-thiazolopyridine)-4-n-propyl] piperazines, the analogous 1-[(2-oxazolopyridine)-4- npropyl] piperazines, 1-[(2-benzothiazole)-4-n-propyl] piperazine and 1-[(2-benzooxazole) 4- n-propyl] piperazine were prepared and in vitro tested as H3-receptor antagonists (the electrically evoked contraction of the guinea-pig jejunum). It appeared that by comparison ...