title: Effects of dopamine and dibutyryl cyclic adenosine monophosphate on delayed release of transmitter at the rat neuromuscular junction.
abstract: The effects of dopamine and dibutyryl cyclic adenosine monophosphate (db-cAMP) on delayed release of transmitter were studied in vitro in the phrenic nerve-diaphragm muscle preparation in the rat using intracellular recording techniques. Dopamine at 1 X 10(-4) mol 1(-1) prevented the initial facilitation of delayed release of transmitter. This inhibitory phase was transformed into a transient facilitation of delayed release. We observed that dopamine hyperpolarized muscle fibres by about 9%. Thus motor nerve terminals may also have been hyperpolarized by dopamine; however, it is unlikely that this hyperpolarization explains the observed effects on delayed release of transmitter. Db-cAMP at 1 X 10(-3) mol 1(-1) predominantly augmented delayed release of acetylcholine. These effects of dopamine and db-cAMP on delayed release of transmitter are discussed in terms of a modulation of calcium fluxes in the presynaptic nerve terminal.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D051381:Rats
chemical_list: D018377:Neurotransmitter Agents; D003994:Bucladesine; D000109:Acetylcholine; D004298:Dopamine