Terminal serotonin autoreceptor function in the rat hippocampus is not modified by pertussis and cholera toxins

Naunyn Schmiedebergs Arch Pharmacol. 1991 Aug;344(2):160-6. doi: 10.1007/BF00167213.


The possibility that the terminal serotonin (5-HT) autoreceptor in the rat hippocampus is coupled to Gi, Go or Gs regulatory proteins was investigated using the electrically evoked overflow of [3H]5-HT from preloaded slices. Pertussis toxin, which inactivates Gi/o or cholera toxin, which stimulates Gs, was injected directly in the hippocampus 3 to 11 days prior to the experiments. Hippocampus slices were prepared, loaded with [3H]5-HT, superfused continuously, and stimulated electrically 72 min (S1) and 116 min (S2) after the beginning of superfusion. In the absence of any drug, the evoked overflow of [3H]5-HT in S1 was not altered by either toxin. The enhancing effect of the 5-HT reuptake blocker paroxetine (1 mumol/l) on the evoked [3H]5-HT overflow was also unaltered by these toxins. 5-Carboxyamidotryptamine, a 5-HT autoreceptor agonist, inhibited in a concentration-dependent manner the stimulation-evoked release of [3H]5-HT. The concentration-effect curve (0.001-0.1 mumol/l) for this drug was not altered by pretreatment with either pertussis or cholera toxin. Similarly, the effect of another 5-HT autoreceptor agonist, 5-methoxytryptamine (0.1 and 1 mumol/l), was not altered in the pretreated rats. In addition, the reduction of [3H]5-HT overflow obtained by increasing the stimulation frequency from 1 Hz to 5 Hz, which is due to an increase in terminal 5-HT autoreceptor activation at the higher frequency, was not altered by either toxin. The enhancing effect of the 5-HT autoreceptor antagonist methiothepin (1 mumol/l) on stimulation-evoked [3H]5-HT overflow was not changed by either pretreatment. N-Ethylmaleimide inactivates Gi/o proteins by alkylation.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-Methoxytryptamine / pharmacology
  • Adenosine Diphosphate Ribose / metabolism
  • Animals
  • Cholera Toxin / pharmacology*
  • Ethylmaleimide / pharmacology
  • GTP-Binding Proteins / physiology
  • Hippocampus / drug effects*
  • Hippocampus / metabolism
  • In Vitro Techniques
  • Male
  • Pertussis Toxin*
  • Rats
  • Rats, Inbred Strains
  • Receptors, Serotonin / drug effects*
  • Receptors, Serotonin / physiology
  • Serotonin / analogs & derivatives
  • Serotonin / metabolism
  • Serotonin / pharmacology
  • Virulence Factors, Bordetella / pharmacology*


  • Receptors, Serotonin
  • Virulence Factors, Bordetella
  • Adenosine Diphosphate Ribose
  • Serotonin
  • 5-Methoxytryptamine
  • Cholera Toxin
  • 5-carboxamidotryptamine
  • Pertussis Toxin
  • GTP-Binding Proteins
  • Ethylmaleimide