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      GABAergic innervation of corticotropin-releasing hormone (CRH)-secreting parvocellular neurons and its plasticity as demonstrated by quantitative immunoelectron microscopy.

      1 ,
      Neuroscience
      Elsevier BV

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          Abstract

          GABA has been identified as an important neurotransmitter in stress-related circuitry mediating inhibitory effects on neurosecretory neurons that comprise the central limb of the hypothalamo-pituitary-adrenocortical axis. Using combinations of pre-embedding immunostaining and postembedding immunogold methods at the ultrastructural level, direct synaptic contacts were revealed between GABA-containing terminals and neurosecretory cells that were immunoreactive for corticotropin-releasing hormone (CRH) in the hypothalamic paraventricular nucleus (PVN). The vast majority of axo-dendritic GABA synapses was symmetric (inhibitory) type, and 46% of all synaptic boutons in the medial parvocellular subdivision of the PVN were immunoreactive to GABA. Using the disector method, an unbiased stereological method on serial ultrathin sections, the total calculated number of synaptic contacts within the medial parvocellular subdivision of the PVN was 55.4 x 10(6)/mm(3). On CRH-positive profiles 20.1 x 10(6) GABAergic synaptic boutons were detected per mm(3) in control, colchicine-treated rats. In the medial parvocellular subdivision, 79% of GABAergic boutons terminated on CRH neurons. Following adrenalectomy, which increases the synthetic and secretory activities of CRH neurons, the number of GABAergic synapses that terminate on CRH-positive profiles was increased by 55%. GABA-containing boutons appeared to be swollen, while the contact surfaces of cellular membranes between GABAergic boutons and CRH-positive profiles were shorter in adrenalectomized animals than in controls. Our data provide ultrastructural evidence for direct inhibitory GABAergic control of stress-related CRH neurons and suggest a pivotal role of GABA-containing inputs in the functional plasticity of parvocellular neurosecretory neurons seen in response to adrenalectomy.

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          Author and article information

          Journal
          Neuroscience
          Neuroscience
          Elsevier BV
          0306-4522
          0306-4522
          2002
          : 113
          : 3
          Affiliations
          [1 ] Laboratory of Molecular Neuroendocrinology, Institute of Experimental Medicine, Szigony u 43 H-1083, Budapest, Hungary.
          Article
          S0306452202001471
          10.1016/s0306-4522(02)00147-1
          12150778
          21470d30-24d3-4eec-b07c-80b47f8d81ed
          History

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