Bdph (mol. wt., 188.23) was synthesized in accordance with the previously described method (Mowry et al. 1949 ; Lin et al. 1984 ) and produced a light-yellow oily substance that is a mixture of 85% trans (Z)- and 15% cis (E)-isomers. Caffeine sodium benzoate (≥98%), dibutyryl adenosine 3′,5′-cyclic-monophosphate (db-cAMP, ≥97%), imidazole (≥99%) and tetrodotoxin (≥98%) were purchased from Sigma-Aldrich (St. Louis, MO). Other drugs used in this study included aminophylline (Eizai, Tokyo, Japan), clonidine (Boehringer-Ingelheim, Ridgefield, CT) and NA (Breon, NY). The final concentrations of the aforementioned drugs in the medium were expressed in molarity.
Male Hartley guinea-pigs (500–600 g, each) were obtained from the Animal Center of the Ministry of Science and Technology, Taipei, Taiwan. The animals were housed in ordinary cages at 22 ± 1 °C with a humidity of 50–60% under a constant 12 h light/dark cycle and were provided with food and water ad libitum. Under a protocol (LAC-74-0032) approved by the Animal Care and Use Committee of Taipei Medical University on 14 October 1985, the GPVD were dissected under anaesthesia (pentobarbital 50 mg/kg, intraperitoneal injection).
Male Hartley guinea-pigs (500–600 g, each) were obtained from the Animal Center of the Ministry of Science and Technology, Taipei, Taiwan. The animals were housed in ordinary cages at 22 ± 1 °C with a humidity of 50–60% under a constant 12 h light/dark cycle and were provided with food and water ad libitum. Under a protocol (LAC-74-0032) approved by the Animal Care and Use Committee of Taipei Medical University on 14 October 1985, the GPVD were dissected under anaesthesia (pentobarbital 50 mg/kg, intraperitoneal injection).