Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

The supraoptic nucleus (SON) provides one of the best model systems in the brain of use-dependent neuron-glial structural plasticity. Both ultrastructural and immunohistochemical studies of the SON have provided evidence that an active retraction and extension of astrocytic processes from between magnocellular neuroendocrine neurons plays a role in the release of oxytocin, and/or vasopressin, that accompanies parturition, lactation and dehydration. Hawrylak et. al. (1998) have demonstrated a reduction in the optical density of GFAP-IR in dehydrated rats that was reversed with rehydration. This indicated changes in the astrocytes' cytoskeleton. The present study applied stereological methods to these specimens to obtain estimates of the surface density (Sv) of GFAP-IR astrocytic processes. In addition, the number of astrocytes was counted. Rats were dehydrated for 7 days by substitution of drinking water with 2% saline, or dehydrated for 7 days followed by 7 days of rehydration. A control group with free access to tap water was used for comparisons. Dehydration resulted in a significant reduction in the Sv of GFAP immunopositive processes in the SON compared to control and rehydrated levels. As expected, no changes were seen in the globus pallidus and lateral hypothalamic regions. The number of astrocytes in the SON was not changed by hydration state. These results are consistent with the changes of optical density GFAP-IR. That the number of astrocytes remained constant strongly suggests a reduction of processes per individual astrocyte. These results provide further evidence for a role of structural plasticity of astrocytes in events surrounding the selective functional activation of local neurons. (Supported by NSF IBN 951457).

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Presentation Number SAhawrylak0850
Keywords: glia, hypothalamus, plasticity, filaments, synapses