Amine modulation of Ih in a small neural network.
We studied the functional role and modulation of the hyperpolarization-activated inward current (I(h)) in the pyloric network of the lobster stomatogastric ganglion. In isolated neurons, I(h) is a small current with a hyperpolarized voltage of half-activation (V(Act)) and a slow time constant of activation (tau(Act)). Bath application of dopamine (DA), octopamine (OCT), or serotonin (5HT) modified I(h) in selected synaptically isolated pyloric neurons. DA significantly enhanced I(h) in the anterior burster (AB) neuron by depolarizing its V(Act), accelerating its tau(Act), and enhancing its maximal conductance (g(max)). DA more weakly enhanced I(h) in the pyloric constrictor (PY) and ventricular dilator (VD) neurons. OCT weakly depolarized V(Act) and accelerated tau(Act) in the VD and inferior cardiac (IC) neurons. 5HT depolarized V(Act) in the IC neuron. Under control conditions with intact modulatory inputs from other ganglia, the pyloric rhythm cycles strongly at about 1-2 Hz. Bath application of the I(h) blocker cesium (Cs(+)) caused a mean increase in the period of 8%, although this effect was highly variable. When Cs(+) was applied to an isolated ganglion where the pyloric rhythm had been activated only by DA, the cycle period was consistently increased by 13.5%, with no other strong changes in rhythm parameters. These results suggest that I(h) regulates the pyloric rhythm by accelerating AB pacemaker frequency, but that this effect can vary with the modulatory conditions.
Peck
Jack H
JH
Department of Psychology, Ithaca College, 1119 Williams Hall, Ithaca, NY 14850, USA. peck@ithaca.edu
Gaier
Eric
E
Stevens
Erin
E
Repicky
Sarah
S
Harris-Warrick
Ronald M
RM
D000465:Algorithms; D000818:Animals; D001679:Biogenic Amines / Q000494:pharmacology*; D054815:Cyclic Nucleotide-Gated Cation Channels; D004298:Dopamine / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000502:physiology; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008839:Microelectrodes; D009132:Muscles / Q000294:innervation / Q000502:physiology; D009415:Nerve Net / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009655:Octopamine / Q000494:pharmacology; D033521:Palinuridae; D018408:Patch-Clamp Techniques; D015221:Potassium Channels; D012701:Serotonin / Q000494:pharmacology
D001679:Biogenic Amines; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D018377:Neurotransmitter Agents; D015221:Potassium Channels; D009655:Octopamine; D012701:Serotonin; D004298:Dopamine