The role of target size in neuronal survival

Abstract

A loss of about half of the trochlear motor neurons occurs during the course of normal development in duck and quail embryos. The role of the size of the target muscle in controlling the number of surviving motor neurons was examined by making motor neurons innervate targets either larger or smaller in size than their normal target. In one experiment the smaller trochlear motor neuron pool of the quail embryo was forced to innervate the larger superior oblique muscle of the duck embryo. This was accomplished by grafting the midbrain of a quail embryo in the place of the midbrain of a duck embryo. Results indicated that no additional quail trochlear motor neurons were rescued in spite of a considerable increase in target size. In another experiment the larger trochlear motor neuron pool of the duck embryo was made to innervate the smaller superior oblique muscle of the quail embryo. This resulted in loss of some additional neurons; however, the number of surviving motor neurons was not proportionate to the reduction in target size. These experiments failed to provide support for the hypothesis that the size of the target muscle controls the number of surviving motor neurons. Although contact with target is necessary for survival of neurons, factors other than the number or size of target cells are involved in the control of motor neuron numbers during development.

Target‐determined expression of α3 isoform of the Na+,K+‐ATPase in the somatic nervous system of rat

“…In mature animals, most of the effects of axotomy on neuronal morphological, biochemical, and physiological properties were attributed to the impairment of the "neuron-target" relationships (Traynor et al, 1992;Tuttle and Steers, 1992;Lowrie and Vrbova, 1992;Sohal, 1992;Caldero et al, 1998). Several observations made in this and our previous studies (Dobretsov et al, 2003) suggest that the expression of ␣ 3 Na ϩ ,K ϩ -ATPase in peripheral neurons of vertebrate animals is yet another mechanism which is controlled by target-derived influences (Fig.…”

The Effect of Cycloheximide and Ganglioside GM1 on the Viability of Retinotectally Projecting Ganglion Cells Following Ablation of the Superior Colliculus in Neonatal Rats

“…The phenomenon is widespread and occurs in both the central and peripheral nervous systems (CNS and PNS). There is considerable evidence that, at certain critical times, developing neurons compete with each other for limited amounts of target-derived neurotrophic factors (for recent reviews see Clarke, 1990;Oppenheim, 1991;Snider er al., 1992;Sohal, 1992); those cells which obtain a necessary and sufficient amount of trophic support survive to maturity.…”

Neurotrophic factor regulation of developing avian oculomotor neurons: Differential effects of BDNF and GDNF

“…Oculomotor axons reach their target prior to cell death (Sohal and Weidman, 1978). The size of the target affects the number of innervating oculomotor neurons (Cowan and Wenger, 1967;Boydston and Sohal, 1979;Tanaka et al, 1987;Sohal, 1992) and death is thought to be a result of competition among axons for limited amounts of target-derived trophic factors. All trophic factors examined in this study (BDNF,and GDNF) are expressed in developing muscle (Griesbeck et al, 1995;Nosrat et al, 1997), and they were retrogradely transported to the oculomotor nuclei.…”

“…The eye muscles of chick embryos are accessible during development in ovo, and the oculomotor (MIII) complex is uniquely segregated to allow easy identification and quantification of the MIII components (Niimi et al, 1958;Isomura, 1973;Heaton and Wayne, 1983;Evinger, 1988). Virtually no information is available about neurotrophic requirements of these nuclei, despite a considerable number of studies on the developing avian oculomotor nuclei (Cowan and Wenger, 1967;Sohal, 1976Sohal, , 1977Sohal and Weidman, 1978;Heaton, 1981;Heaton and Wayne, 1983;Sohal, 1992;Sohal et al, 1992). For other cranial and spinal motoneurons, the neurotrophic factors BDNF, neurotrophin 4 (NT-4), and glial cell line-derived neurotrophic factor (GDNF) have been shown to act as survival factors (Koliatsos et al, 1993;Yan et al, 1993Yan et al, , 1995Henderson et al, 1994;Zurn et al, 1994Zurn et al, , 1996Lindsay, 1995;Oppenheim et al, 1995;Gimenez y Ribotta et al, 1997).…”