Rationale: It has been postulated that the tride-capeptide neurotensin (NT) functions as an endogenous antipsychotic peptide. A critical test of this hypothesis would be to determine if NT is involved in the expression of latent inhibition (LI), a psychophysiological and pharmacological model of schizophrenia. Objective: This report describes the effects of disrupting NT neurotransmis-sion by systemic administration of the NT receptor antagonists SR48692 and SR142948A on the acquisition of LI in rats.Methods: The effects of 30-300 μg/kg SR48692 or 0.1-100 μg/kg SR142948A on the expression of LI following 0, 20 or 30 pre-exposures were first investigated. This was followed by the assessment of the effects of 10 μg/kg SR142948 A on the LI effect of increasing stimulus pre-exposures (10-40). Finally, the role of dopamine transmission in the effects of SR142948A on the acquisition of LI (30 pre-exposures) was tested by coadminister-ing 10 μg/kg SR142948A and 100 mg/kg of the dopamine D2 antagonist sulpiride. Results: The higher tested doses of SR48692 (100-300 μg/kg) and SR142948A (10-100 μg/kg) decreased acquisition of LI following 20, 30 and even 40 pre-exposures to the to-be-conditioned stimulus. Cotreatment with the dopamine D2 antagonist sulpiride prevented the LI-disrupting effects of SR142948A. Conclusions: NT neurotransmission appears to be necessary for the acquisition of LI. The main effect of NT receptor antagonism is a disruption of LI, most likely via enhancement of dopamine transmission. This effect is opposite that of antipsychotic drugs, which have been shown to enhance NT release, supporting the hypothesis of NT as an endogenous antipsychotic peptide.
- Conditioned emotional response
- Latent inhibition
- SR 142948A
- SR 48692
ASJC Scopus subject areas