Characteristics of outward current induced by application of dopamine on a snail neuron

Nesić, O.; Pasić, M.

Comparative Biochemistry and Physiology. C Comparative Pharmacology and Toxicology 103(3): 597-606


ISSN/ISBN: 0742-8413
PMID: 1363311
DOI: 10.1016/0742-8413(92)90187-c
Accession: 008290818

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A closer characterization of the potassium channel opened by the application of dopamine (DA) on an identified Helix pomatia neuron was attempted. The effect of K+ channel blockers (TEA and 4-AP) on the DA-induced current was examined. The results indicate that the channel opened by DA does not share the pharmacological properties of other snail neuron K-channels. The I-V relation for I-DA was successfully fitted by the Constant Field equation except below the reversal potential where the current was smaller than expected. The assumption that DA binding is voltage-sensitive is supported by the increment of the Hill coefficient with hyperpolarization (from n-H simeq 1 to n-H simeq 2). The presence of the phosphodiesterase inhibitor IBMX does not affect the DA induced outward current. However, the assumption that the snail neurons' DA receptor belongs to the D-2 class is in contrast to the antagonistic effects of ergot alkaloids which, in mammalian neurons, are competitive antagonists of D-1 receptors. The examination of the voltage-sensitivity of the blocking action of the ergot alkaloid (Bromoergocryptinine) revealed that it does not compete with DA for the same binding site as in mammalian D-1 receptors.