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Retroambiguus Projections to the Cutaneus Trunci Motoneurons May Form a Pathway in the Central Control of Mating

Retroambiguus Projections to the Cutaneus Trunci Motoneurons May Form a Pathway in the Central... Abstract Our laboratory has proposed that the nucleus retroambiguus (NRA) generates the specific motor performance displayed by female cats during mating and that it uses direct pathways to the motoneurons of the lower limb muscles involved in this activity. In the hamster a similar NRA-projection system could generate the typical female mating posture, which is characterized by lordosis of the back as well as elevation of the tail. The present study attempted to determine whether this elevation of the tail is also part of the NRA-mating control system. The basic assumption was that elevation of the tail is a function of the cutaneus trunci muscle (CTM), which was verified by bilateral tetanic stimulation of the lateral thoracic nerves innervating the CTM. It resulted in upward movement of the tail to a position similar to the tail-up position during the lordosis posture. Retrograde tracing results showed that CTM motoneurons are located in the ventral and ventrolateral part of the C 7 –C 8 ventral horn, those innervating the tail region ventrolateral to those innervating the axillary region. Anterograde tracing studies showed that NRA fibers terminate bilaterally in both parts of the CTM motoneuronal cell groups. Electron microscopical studies revealed that labeled NRA terminals make monosynaptic contacts with retrogradely labeled dendrites of CTM motoneurons. Almost all of these terminal profiles had asymmetric synapses and contained spherical vesicles, which suggests an excitatory function. The observation that 15% of the labeled NRA terminals make more than one synaptic contact with a retrogradely labeled CTM motoneuronal dendrite within the same section indicates how powerful the NRA-CTM projection is. The results indicate that during mating the NRA not only could generate the lordosis posture but also the elevation of the tail. Footnotes Address for reprint requests: P. O. Gerrits, Dept. of Anatomy and Embryology, University of Groningen, Faculty of Medicine, Oostersingel 69, 9713 EZ Groningen, The Netherlands. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2000 The American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neurophysiology The American Physiological Society

Retroambiguus Projections to the Cutaneus Trunci Motoneurons May Form a Pathway in the Central Control of Mating

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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0022-3077
eISSN
1522-1598
Publisher site
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Abstract

Abstract Our laboratory has proposed that the nucleus retroambiguus (NRA) generates the specific motor performance displayed by female cats during mating and that it uses direct pathways to the motoneurons of the lower limb muscles involved in this activity. In the hamster a similar NRA-projection system could generate the typical female mating posture, which is characterized by lordosis of the back as well as elevation of the tail. The present study attempted to determine whether this elevation of the tail is also part of the NRA-mating control system. The basic assumption was that elevation of the tail is a function of the cutaneus trunci muscle (CTM), which was verified by bilateral tetanic stimulation of the lateral thoracic nerves innervating the CTM. It resulted in upward movement of the tail to a position similar to the tail-up position during the lordosis posture. Retrograde tracing results showed that CTM motoneurons are located in the ventral and ventrolateral part of the C 7 –C 8 ventral horn, those innervating the tail region ventrolateral to those innervating the axillary region. Anterograde tracing studies showed that NRA fibers terminate bilaterally in both parts of the CTM motoneuronal cell groups. Electron microscopical studies revealed that labeled NRA terminals make monosynaptic contacts with retrogradely labeled dendrites of CTM motoneurons. Almost all of these terminal profiles had asymmetric synapses and contained spherical vesicles, which suggests an excitatory function. The observation that 15% of the labeled NRA terminals make more than one synaptic contact with a retrogradely labeled CTM motoneuronal dendrite within the same section indicates how powerful the NRA-CTM projection is. The results indicate that during mating the NRA not only could generate the lordosis posture but also the elevation of the tail. Footnotes Address for reprint requests: P. O. Gerrits, Dept. of Anatomy and Embryology, University of Groningen, Faculty of Medicine, Oostersingel 69, 9713 EZ Groningen, The Netherlands. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2000 The American Physiological Society

Journal

Journal of Neurophysiology – The American Physiological Society

Published: May 1, 2000

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