Further identification of multiple responses mediated by dopamine in the CNS of Planorbis corneus

Intracellular recordings from neurones, receiving monosynaptic contacts from a dopamine-containing (DA-containing) neurone in the central ganglia of the gastropod mollusc Planorbis corneus, revealed that there are at least three DA-mediated responses. These are 'fast' excitatory postsynaptic potentials (EfPSPs) (200 ms), 'slow' excitatory postsynaptic potentials (EsPSPs) (900 ms), and inhibitory postsynaptic potentials (IPSPs) (200–900 ms). Various combinations of these synaptic potentials were recorded from postsynaptic neurones: EsPSPs, EfPEPs, EsEfPSPs, or EfIPSPs. Neurones receiving such connections also responded appropriately to iontophoresized DA with a 'fast' depolarization (EfPSPs), a 'slow' depolarization (EsPSPs), or a hyperpolarization (IPSPs). These responses could be distinguished on the basis of function (excitation or inhibition), duration, rate of desensitization, and sensitivity to apomorphine, D-LSD, and tubocurarine. The neuroleptic drugs (DA antagonists) haloperidol, fluphenazine, and...