Prenatal development of somatosensory primary afferent connections in the sheep

Reproduction, Fertility, and Development
S ReesJ Rawson

Abstract

A summary is presented of recently published studies on the structural and functional development of cutaneous and muscle receptors and the connections of their afferent fibres in fetal sheep (n = 26) aged between 67 and 143 days gestation (term, 146 days). In these studies it was shown that primary afferent fibres projected to, and made synaptic connections with, dorsal horn neurons in lumbosacral spinal cord by 56-61 days gestation. Sensory innervation of the skin occurred later by about 75 days gestation and, at this age, stimulation of the skin first activated cutaneous afferent fibres and evoked a discharge in dorsal root ganglion and dorsal horn neurons. Muscle stretch first activated muscle spindles and evoked a discharge in dorsal root ganglion cells by about 75 days. Prior to this (by about 67 days) primary afferent fibres had begun to innervate motoneuron pools in the spinal cord, and motor nerves had begun to innervate muscle fibres. Both muscle spindle and cutaneous innervation were relatively simple at mid gestation indicating that the structure of sensory receptors need not be complex in order to generate a response. Neural pathways necessary for reflex activity involving muscle spindles are therefore present and ...Continue Reading

Citations

May 20, 2004·The Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society·Haoshu LuoZhongxia Liu
Sep 13, 2007·Physiological Genomics·A S BordersT V Getchell
Sep 25, 2018·Frontiers in Neurology·Melissa A TadrosRobert J Callister

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