, Volume 125, Issue 3, pp 231–237 | Cite as

Functional behavioral homology between rat 5-HT1B and guinea pig 5-HT1D receptors in the modulation of prepulse inhibition of startle

  • T. E. Sipes
  • M. A. Geyer
Original Investigation


The serotonin (5-HT) 1B receptor in rats and mice appears to be homologous to the 5-HT1D receptor found in other mammals, such as guinea pigs and humans. The present series of experiments explored the functional similarity between the rat 5-HT1B receptor and the guinea pig 5-HT1D receptor on two behavioral measures known to be influenced by 5-HT1B receptor manipulations in rats: prepulse inhibition of the startle response (PPI) and locomotor activity. Because the 5-HT1B agonist RU 24969 disrupts PPI and stimulates locomotor behavior in rats, it was predicted that the 5-HT1D agonist, SDZ 219–964, would demonstrate a similar behavioral profile in guinea pigs. In support of this hypothesis, SDZ 219–964 was found to disrupt PPI dose-dependently (1.0 and 2.0 mg/kg) without significantly affecting startle amplitude and to increase locomotor activity (0.5–2.0 mg/kg) in guinea pigs. In guinea pigs, RU 24969 failed to affect PPI, although it did increase locomotor activity, indicating that RU 24969 may have activity at the 5-HT1D receptor. As expected, RU 24969 in rats disrupted PPI (2.5 and 5.0 mg/kg) and significantly increased locomotor activity (1.25–5.0 mg/kg). In rats, however, SDZ 219–964 had generalized, stimulatory effects on startle reactivity, without independent effects on PPI or locomotor activity. The spatial patterns of locomotion exhibited by guinea pigs treated with SDZ 219–964 versus those of rats treated with RU 24969 demonstrate important qualitative differences in structure, indicating that the neural substrates subserving these effects may be different. It is concluded that a functional similarity exists between 5-HT1D and 5-HT1B receptors with regard to the modulation of sensorimotor inhibition and, to a lesser extent, locomotor activity.

Key words

5-HT1B 5-HT1D Guinea pig Rat Locomotor activity Prepulse inhibition Startle Serotonin 


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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • T. E. Sipes
    • 1
  • M. A. Geyer
    • 2
  1. 1.Department of NeuroscienceUniversity of California at San DiegoLa JollaUSA
  2. 2.Department of PsychiatryUniversity of California at San DiegoLa JollaUSA

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