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5-HT mechanisms of median raphe nucleus in the conditioned freezing caused by light/foot-shock association.
Physiol Behav. 2003 Mar; 78(3):471-7.PB

Abstract

We have shown that 5-HT mechanisms of the median raphe nucleus (MRN) are involved in contextual fear-conditioning processes as electrolytic or neurotoxic lesions with N-methyl-D-aspartate (NMDA) or injections of 8-hydroxy-2-(di-n-propilamino)-tetralin (8-OH-DPAT) into this structure inhibit freezing behavior in a contextual fear paradigm. In this work, we extend these studies by analyzing the behavioral responses in a classical fear-conditioning paradigm (light or tone/foot-shock association) in rats with either neurochemical lesion with NMDA or injected with 8-OH-DPAT into the MRN. The animals received NMDA or 8-OH-DPAT or saline microinjections into the MRN and were submitted to conditioning trials in an experimental chamber, where they received 10 foot-shocks (0.6 mA, 1 s, variable interval between 10 and 50 s) paired with tone or light (CS). On the next day, they were tested in a different experimental chamber, with or without CS presentation, where the duration of freezing and the number of rearing episodes were recorded. Light or tone alone caused a significant amount of freezing. NMDA lesions or 8-OH-DPAT injections into the MRN clearly inhibited freezing behavior in rats conditioned to light/foot-shock association, but not in the conditioning sessions with tones. Besides the proposed role in contextual fear conditioning, these results clearly show that MRN is involved in the fear conditioning with light as conditioned stimuli. Distinct neural substrates seem to subserve conditioning fear with acoustic stimuli.

Authors+Show Affiliations

Laboratório de Psicobiologia, FFCLRP, Campus USP, Av Bandeirantes 3900, 14049-901, Ribeirão Preto, SP, Brazil.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12676284

Citation

Avanzi, V, et al. "5-HT Mechanisms of Median Raphe Nucleus in the Conditioned Freezing Caused By Light/foot-shock Association." Physiology & Behavior, vol. 78, no. 3, 2003, pp. 471-7.
Avanzi V, Silva RC, Macedo CE, et al. 5-HT mechanisms of median raphe nucleus in the conditioned freezing caused by light/foot-shock association. Physiol Behav. 2003;78(3):471-7.
Avanzi, V., Silva, R. C., Macedo, C. E., & Brandão, M. L. (2003). 5-HT mechanisms of median raphe nucleus in the conditioned freezing caused by light/foot-shock association. Physiology & Behavior, 78(3), 471-7.
Avanzi V, et al. 5-HT Mechanisms of Median Raphe Nucleus in the Conditioned Freezing Caused By Light/foot-shock Association. Physiol Behav. 2003;78(3):471-7. PubMed PMID: 12676284.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - 5-HT mechanisms of median raphe nucleus in the conditioned freezing caused by light/foot-shock association. AU - Avanzi,V, AU - Silva,R C B, AU - Macedo,C E, AU - Brandão,M L, PY - 2003/4/5/pubmed PY - 2003/8/21/medline PY - 2003/4/5/entrez SP - 471 EP - 7 JF - Physiology & behavior JO - Physiol Behav VL - 78 IS - 3 N2 - We have shown that 5-HT mechanisms of the median raphe nucleus (MRN) are involved in contextual fear-conditioning processes as electrolytic or neurotoxic lesions with N-methyl-D-aspartate (NMDA) or injections of 8-hydroxy-2-(di-n-propilamino)-tetralin (8-OH-DPAT) into this structure inhibit freezing behavior in a contextual fear paradigm. In this work, we extend these studies by analyzing the behavioral responses in a classical fear-conditioning paradigm (light or tone/foot-shock association) in rats with either neurochemical lesion with NMDA or injected with 8-OH-DPAT into the MRN. The animals received NMDA or 8-OH-DPAT or saline microinjections into the MRN and were submitted to conditioning trials in an experimental chamber, where they received 10 foot-shocks (0.6 mA, 1 s, variable interval between 10 and 50 s) paired with tone or light (CS). On the next day, they were tested in a different experimental chamber, with or without CS presentation, where the duration of freezing and the number of rearing episodes were recorded. Light or tone alone caused a significant amount of freezing. NMDA lesions or 8-OH-DPAT injections into the MRN clearly inhibited freezing behavior in rats conditioned to light/foot-shock association, but not in the conditioning sessions with tones. Besides the proposed role in contextual fear conditioning, these results clearly show that MRN is involved in the fear conditioning with light as conditioned stimuli. Distinct neural substrates seem to subserve conditioning fear with acoustic stimuli. SN - 0031-9384 UR - https://www.unboundmedicine.com/medline/citation/12676284/5_HT_mechanisms_of_median_raphe_nucleus_in_the_conditioned_freezing_caused_by_light/foot_shock_association_ DB - PRIME DP - Unbound Medicine ER -