K+ channel and 5-hydroxytryptamine1A autoreceptor interactions in the rat dorsal raphe nucleus: an in vitro electrophysiological study

Neuroscience. 1991;41(2-3):495-505. doi: 10.1016/0306-4522(91)90344-n.


Extracellular recordings were made from serotonergic neurons of the rat dorsal raphe nucleus in a slice preparation. In the presence of phenylephrine (3 microM) to restore the pacemaker activity of otherwise silent serotonergic neurons, superfusion with the 5-hydroxytryptamine1A agonist ipsapirone depressed the firing of these neurons with an IC50 of approximately 50 nM. Complete inhibition was achieved with 100-300 nM of the drug. Concomitant superfusion with the 5-hydroxytryptamine1A antagonists spiperone (100 nM) or propranolol (10 microM) markedly reduced the inhibitory effect of ipsapirone (100 nM). Superfusion with K+ channel blockers such as apamin (50-100 nM), charybdotoxin (100 nM) or Ba2+ (1 mM) did not induce any changes in the electrical activity of serotonergic neurons. However, 4-aminopyridine (0.1-1 mM) disrupted the regularity of their discharge without affecting the mean firing rate. The ipsapirone-induced inhibition was unchanged by apamin and charybdotoxin, but was markedly reduced by Ba2+ and 4-aminopyridine. Thus the IC50 of ipsapirone was shifted to approximately 150 nM in the presence of 1 mM of 4-aminopyridine. These results indicate that, in serotonergic neurons within the dorsal raphe nucleus, the K+ channel opened through the stimulation of 5-hydroxytryptamine1A autoreceptors is 4-aminopyridine-sensitive.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Aminopyridine / pharmacology
  • Animals
  • Anti-Anxiety Agents
  • Apamin / pharmacology
  • Barium / pharmacology
  • Charybdotoxin
  • Electrophysiology / methods
  • Evoked Potentials / drug effects
  • Male
  • Neurons / drug effects
  • Neurons / physiology*
  • Phenylephrine / pharmacology
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Propranolol / pharmacology
  • Pyrimidines / pharmacology
  • Raphe Nuclei / drug effects
  • Raphe Nuclei / physiology*
  • Rats
  • Rats, Inbred Strains
  • Receptors, Serotonin / drug effects
  • Receptors, Serotonin / physiology*
  • Scorpion Venoms / pharmacology
  • Spiperone / pharmacology


  • Anti-Anxiety Agents
  • Potassium Channels
  • Pyrimidines
  • Receptors, Serotonin
  • Scorpion Venoms
  • Charybdotoxin
  • Phenylephrine
  • Apamin
  • Barium
  • Spiperone
  • ipsapirone
  • Propranolol
  • 4-Aminopyridine