Cortical refractoriness to N-methyl-d, l-aspartic acid (NMA) stimulation in the lactating rat: recovery after pup removal and blockade of progesterone receptors

Rula Abbud, Gloria E. Hoffman, M. Susan Smith

    Research output: Contribution to journalArticlepeer-review

    30 Scopus citations

    Abstract

    We have previously reported that lactating rats, unlike cycling rats, are refractory to N-methyl-d,l-aspartic acid (NMA), but not kainate, in terms of behavioral responses and activation of cFos expression in the neocortex and hippocampus. To study the factors involved in the suppression of cortical activation in lactating rats in response to NMA, we examined the effects of removing either the suckling stimulus and/or progesterone. The degree of cFos expression was used as a marker for cortical activation. Whereas control suckled animals exhibited little or no cFos activation in the piriform cortex in response to NMA, cycling rats showed a high degree of activation. Blockade of the effects of progesterone or removal of the pups for 24 h, resulted in a moderate level of cFos intensity in response to NMA. Total recovery was observed only in animals who had their pups removed for 24 h and the effects of progesterone were blockad. In general, similar results were obtained in the hippocampus except that the total recovery of hippocampal activation took longer than the cortex. Thus, the deficits in cortical activation depend on the presence of both the suckling stimulus and progesterone. However, progesteron alone cannot induced these cortical deficits since pregnant rats showed no deficits in cortical activation in response to NMA when compared to cycling rats. Therefore, the suckling stimulus is required for the inhibition of NMDA-receptor mediated activation of the cortex and hippocampus. The effects of progesterone appear to act synergistically with the effects of suckling.

    Original languageEnglish (US)
    Pages (from-to)16-23
    Number of pages8
    JournalBrain research
    Volume604
    Issue number1-2
    DOIs
    StatePublished - Feb 26 1993

    Keywords

    • CFos expression
    • Cortical activation
    • Lactation
    • N-Methyl-d,l-aspartic acid
    • N-Methyl-d-aspartate receptor inactivation
    • progesterone

    ASJC Scopus subject areas

    • Neuroscience(all)
    • Molecular Biology
    • Clinical Neurology
    • Developmental Biology

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