TY - JOUR T1 - Effects of multiple exposures to D-cycloserine on extinction of conditioned fear in rats. AU - Parnas,A Sophie, AU - Weber,Marianne, AU - Richardson,Rick, PY - 2004/04/16/received PY - 2004/09/21/revised PY - 2005/01/01/accepted PY - 2005/4/12/pubmed PY - 2005/7/23/medline PY - 2005/4/12/entrez SP - 224 EP - 31 JF - Neurobiology of learning and memory JO - Neurobiol Learn Mem VL - 83 IS - 3 N2 - Previous research has shown that an acute, post-training injection of D-cycloserine (DCS) facilitates extinction of conditioned fear in rats; however, the effects of multiple exposures to DCS in this situation are not known. In Experiment 1, rats were conditioned (light-shock pairings) and 24 h later given six extinction (light-alone) trials followed by an injection of DCS (15 mg/kg) or saline. The next day, all rats were tested for light-elicited freezing. In Experiment 2, the effect of DCS on extinction was tested in the same manner, except that rats were pre-exposed to DCS (0, 1, or 5 injections) just prior to conditioning. In Experiment 3, rats received five pre-exposures of DCS but conditioning occurred either 2 or 28 days after the last pre-exposure. The results showed that DCS facilitated extinction of conditioned freezing to the light CS when no drug pre-exposure had occurred, but pre-exposure to DCS just prior to conditioning disrupted the facilitation of extinction effect. When 28 days were interposed between pre-exposure and conditioning, the facilitatory effects of DCS on extinction were restored. These findings suggest that DCS has significant clinical value but that behavioral desensitization may occur with multiple exposures; however, desensitization is not permanent and is reduced by the passage of time. SN - 1074-7427 UR - https://www.unboundmedicine.com/medline/citation/15820858/Effects_of_multiple_exposures_to_D_cycloserine_on_extinction_of_conditioned_fear_in_rats_ DB - PRIME DP - Unbound Medicine ER -