Cambios plásticos de adaptación ultra estructural de las conexiones nerviosas motoras en el adulto en respuesta a un incremento fisiológico de la actividad

Identifier:  TDX:647

Handle: https://hdl.handle.net/20.500.11797/TDX647

Authors:  Santafé i Martínez, Manel

Abstract:
The activity pattern of neuromuscular junctions can influence the structure, growth and remodeling responses and differentiation of the motor nerve terminals. Nerve terminal remodeling involving changes of growth and retraction in the normal adult are affected by the level of the animal's activity. In fact, nerve terminal retraction in the adult can be induced by the level of increased synaptic activity. In the present work we tried to analyze if a small physiologic increase in the locomotor's activity of the normal adult rats during a brief period of time can induce pre- and postsynaptic ultrastructural adaptations.MATERIAL AND METHODS: The Extensor Digitorum Longus (E.D.L.) muscles of 24 three-month-old male Sprague-Dawley rats were studied. The experimental animals spontaneously adapted to the moderately exercise by training a treadmill. Normally housed rats were used as controls. The neural zones from the right and left E.D.L. muscles were fixed in glutaraldehyde and conventionally processed for T.E.M. Cross-sectioned different end plates were directly recorded in magnetic support with a high definition video system. Morphometric analysis of pre- and postsynaptic structural parametres was performed with a semiautomatic image analysis system (MOP VIDEOPLAN).MAIN CONCLUSIONS: 1- Axonal retraction in normal muscles can be compensated by the following changes in the neurotransmission-related structures: Synaptic vesicles increase in diameter and also increase the number of synaptic vesicles in contact with the synaptic axolemma; active zones increase in number; postsynaptic membrane densifications decrease in length and that is compensated by an increase in number of these.2- The morphometric data clearly indicate that small and early physiological changes in the locomotor's activity in the normal adult are followed by precise morphologic adaptations. The increased differentiation of postsynaptic membrane densifications would suggest the existence of the postsynaptic compensatory mechanism for the presynaptic retraction.