Effects of Serotonin Inhibition on Neuronal and Astrocyte Plasticity in the Phrenic Nucleus 4 h Following C2 Spinal Cord Hemisection

• Published in: Experimental neurology 1999-12, Vol.160 (2), p.433-445
• Main Authors: Hadley, Scott D., Walker, Paul D., Goshgarian, Harry G.
• Format: Article
• Language: English
• Subjects: Animals; astrocyte; Astrocytes - drug effects; Astrocytes - physiology; Astrocytes - ultrastructure; Axons - physiology; Axons - ultrastructure; Biological and medical sciences; Dendrites - physiology; Dendrites - ultrastructure; Female; Fenclonine - pharmacology; glial fibrillary acidic protein; Glial Fibrillary Acidic Protein - analysis; Immunohistochemistry; Injuries of the nervous system and the skull. Diseases due to physical agents; Medical sciences; Motor Neurons - drug effects; Motor Neurons - physiology; Motor Neurons - ultrastructure; Neuroglia - drug effects; Neuroglia - physiology; Neuroglia - ultrastructure; Neuronal Plasticity - drug effects; para-chlorophenylalanine; Phrenic Nerve - physiopathology; plasticity; Rats; Rats, Sprague-Dawley; Serotonin Antagonists - pharmacology; Spinal Cord - pathology; Spinal Cord - physiopathology; Spinal Cord - ultrastructure; Spinal Cord Injuries - physiopathology; spinal cord injury; Synapses - physiology; Synapses - ultrastructure; synaptic active zone; Time Factors; Traumas. Diseases due to physical agents
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1006/exnr.1999.7238

C2 spinal cord hemisection results in synaptic and astroglial changes in the phrenic nucleus which have been associated with the recovery of the ipsilateral hemidiaphragm during expression of the crossed phrenic phenomenon. As part of our ongoing analysis of the neurotransmitters involved, the present study investigated the effects of systemic administration of para-chlorophenylalanine (p-CPA), a serotonin (5-HT) synthesis inhibitor, on plasticity in the rat phrenic nucleus 4 h following C2 hemisection. Hemisected control rats demonstrated typical morphological changes in the ipsilateral phrenic nucleus including: (1) an increased number and length of synaptic active zones and (2) an increased number and length of dendrodendritic membrane appositions. p-CPA treatment 3 days prior to hemisection reduced 5-HT levels and resulted in an attenuation of these changes in the ipsilateral phrenic nucleus 4 h following hemisection compared to hemisected controls. In addition, p-CPA treatment attenuated injury-induced alterations in immunohistochemical staining of glial fibrillary acidic protein (GFAP), although Western blot analysis demonstrated that overall levels of GFAP did not differ significantly between groups. The results suggest that inhibition of 5-HT synthesis by p-CPA attenuates hemisection-induced plasticity in the phrenic nucleus 4 h following an ipsilateral C2 hemisection.