The head-twitch response in the least shrew (Cryptotis parva) is a 5-HT2- and not a 5-HT1C-mediated phenomenon

Document Type

Article

Publication Title

Pharmacology, Biochemistry and Behavior

Abstract

Our initial studies suggested that the 5-HT2/1C agonist (±)-1-(2,5-dimethoxy-4-iodophenyl-2-aminopropane[(±)-DOI] produces both the head-twitch response (HTR) and the ear-scratch response (ESR) in mice via stimulation of 5-HT2 receptors. However, challenge studies revealed that these behaviors are produced via two different receptors (possibly 5-HT2 and 5-HT1C). Due to a lack of selective agents one cannot designate a particular response for the activation of a specific receptor. The purpose of the present study was to investigate such behaviors in the least shrew, which is more sensitive to (±)-DOI than rodents. IP injection of (±)-DOI in shrews produced a dose-dependent (bell-shaped) and time-dependent increase in the HTR frequency. The (±)-DOI-induced HTR was equipotently and completely attenuated by the 5-HT2/1C antagonists ketanserin and spiperone. The 5-HT1C antagonists with 5-HT2 agonist action, lisuride, also produced the HTR in a bell-shaped dose- and time-dependent fashion. Central injections of both (±)-DOI (0.2 μg) and lisuride (0.5 μg) also induced the behavior. Both peripheral and central administration of lisuride failed to produce the ESR. (±)-DOI significantly induced the ESR only at the highest dose tested (2.5 mg/kg, IP). Centrally administered (±)-DOI (0.2 μg) produced more ESRs relative to vehicle controls; however, the difference did not attain significance. At low doses (0.31 and 0.63 mg/kg), (±)-DOI had no effect on locomotor activity, but it significantly attenuated the behavior at larger doses. Both low and high doses of lisuride increased the motor activity. Spiperone dose-dependently suppressed locomotion, whereas ketanserin had no effect. The present results suggest that the HTR is a 5-HT2 receptor-mediated event and changes in locomotor activity do not affect the induced HTR. © 1994.

First Page

383

Last Page

396

DOI

10.1016/0091-3057(94)90542-8

Publication Date

1-1-1994

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