Embryonic stem (ES) cells differentiate into functional motoneurons when treated with a sonic hedgehog (Shh) agonist and retinoic acid (RA). Whether ES cells can be directed to differentiate into specific subtypes of motoneurons is unknown. We treated embryoid bodies generated from HBG3 ES cells with a Shh agonist and RA for 5 d in culture to induce motoneuron differentiation. Enhanced green fl...

In cultured chicken myotubes, calcitonin gene-related peptide (CGRP), a peptide present in spinal cord motoneurons, increased by 1.5-fold the number of surface acetylcholine receptors (AChRs) and by threefold AChR alpha-subunit mRNA level without affecting the level of muscular alpha-actin mRNA. Cholera toxin (CT), an activator of adenylate cyclase, produced a similar effect, which did not add ...

We have observed the development of live, fluorescently labeled motoneurons in the spinal cord of embryonic and larval zebrafish. There are 2 classes of motoneurons: primary and secondary. On each side of each spinal segment there are 3 individually identifiable primary motoneurons, named CaP, MiP, and RoP. The motoneurons of the embryo and larva are similar in morphology and projection pattern...

We have studied synaptic connections between individual stretch-sensitive muscle afferents and motoneurons in the brachial spinal cord of bullfrogs. Sensory afferents from a given head of the triceps brachii muscle preferentially innervate motoneurons that project to the same muscle head. This preference is characterized in two ways: each class of sensory axon innervates a greater proportion of...

During walking, maintenance and coordination of activity in leg motoneurons requires intersegmental signal transfer. In a semi-intact preparation of the stick insect, we studied membrane potential modulations in mesothoracic (middle leg) motoneurons and local premotor nonspiking interneurons that were induced by stepping of a front leg on a treadmill. The activity in motoneurons ipsi- and contr...

Internal intercostal and abdominal motoneurons are strongly coactivated during expiration. We investigated whether that synergy was paralleled by synergistic Group I reflex excitation. Intracellular recordings were made from motoneurons of the internal intercostal nerve of T8 in anesthetized cats, and the specificity of the monosynaptic connections from afferents in each of the two main branche...

Heterotrimeric guanine nucleotide-binding proteins (G proteins) act as signal-transducing molecules that connect serpentine-transmembrane receptors to a variety of intracellular effectors. We characterized a Caenorhabditis elegans G(s) gene, gsa-1, which encodes a G(s) alpha-subunit (G alpha(s)) that is expressed throughout the nervous system and in muscle cells. gsa-1 is an essential gene; a l...

Individually identified primary motoneurons of the zebrafish embryo pioneer cell-specific peripheral motor nerves. Later, the growth cones of secondary motoneurons extend along pathways pioneered by primary motor axons. To learn whether primary motor axons are required for pathway navigation by secondary motoneurons, we ablated primary motoneurons and examined subsequent pathfinding by the grow...

In the rat cervical spinal cord the corticospinal projection on motoneurons either direct or indirect (via interneurons) comes about postnatally making it accessible for experimental research. Therefore, the postnatal developmental changes of motoneurons and in particular their dendritic fields were examined. Motoneurons innervating the two antagonistic muscles in the distal forepaw, the m. fle...

During walking, maintenance and coordination of activity in leg motoneurons requires intersegmental signal transfer. In a semi-intact preparation of the stick insect we studied membrane potential modulations in mesothoracic (middle leg) motoneurons and local premotor non-spiking interneurons that were induced by stepping of a front leg on a treadmill. The activity in motoneurons ipsilateral and...