Inhibition of N- and L-type Ca2+ currents by dopamine in lamprey spinal motoneurons.
Dopamine is co-localized with 5-hydroxytryptamine in a ventromedially located plexus in the lamprey spinal cord and reduces Ca2+ currents in motoneurons that express high-voltage activated Ca2+ currents of the N-, L- and P/Q-types. Blockade of L- and P/Q- type channels leaving N-type channels intact reduced but did not prevent the inhibition of the Ca2+ current by dopamine. Dopamine also reduced the L-type current potentiated by BAY K 8644. During simultaneous blockade of N-type and L-type currents, dopamine was unable to affect the remaining Ca2+ current. In addition, blockade of G-proteins abolished the dopaminergic modulation. The inhibition was unaffected by depolarizing prepulses. Thus, dopamine mediates inhibition of N- and L-type currents through a G-protein-dependent, voltage-independent pathway in lamprey spinal motoneurons.
Wikström
M A
MA
Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Grillner
S
S
El Manira
A
A
D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000502:physiology*; D020864:Calcium Channels, N-Type / Q000187:drug effects* / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology* / Q000502:physiology*; D004594:Electrophysiology; D019204:GTP-Binding Proteins / Q000502:physiology; D007798:Lampreys / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology*; D009046:Motor Neurons / Q000187:drug effects* / Q000502:physiology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D017448:Receptors, Dopamine D2 / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D017448:Receptors, Dopamine D2; D019204:GTP-Binding Proteins; D004298:Dopamine