Histamine dihydrochloridewas

Histamine dihydrochloride
was purchased from Alfa Aesar GmbH & Co. KG (Karlsruhe, Germany).
[³H]mepyramine (specific activity: 20.0 Ci/mmol), [³H]tiotidine (specific activity: 78.4 Ci/mmol), [³H]N^α-methylhistamine (specific
activity: 85.3 Ci/mmol), and [³H]histamine (specific activity:
25.0 Ci/mmol) were obtained from Hartmann Analytic (Braunschweig,
Germany). GTPγS was purchased from Roche (Mannheim, Germany),
and [³⁵S]GTPγS was purchased from PerkinElmer Life
Science (Boston) or Hartmann Analytic (Braunschweig, Germany). [³H]UR-DE257 was synthesized in our laboratories. All stock
solutions were dissolved in millipore water or in a mixture of Millipore
water/DMSO. In all assays, the final DMSO content amounted to <0.5%.

NaCl, KCl, MgCl₂·6H₂O, CaCl₂, N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) (HEPES), d-glucose,
1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic
acid (BAPTA-AM), cytochalasin D, triprolidine hydrochloride, and pyrilamine
maleate salt were purchased from Sigma-Aldrich. Histamine dihydrochloride
was purchased from Alfa Aesar. Deionized water was used to prepare
all the buffers.