The purpose of this study was to examine the effects of axon transection on the development and differentiation of spinal motoneurons in the bullfrog (Rana catesbeiana) tadpole. The 3 ventral roots (VRs) that innervate the hindlimb were transected, and the animals were killed 6-7 weeks later (reinnervation took place within 3 weeks). At early stages of development, axotomy resulted in an increa...

1. Chronically implanted microelectrode wires in the L7 and S1 dorsal root ganglia were used to record unit activity from cat hindlimb primary and secondary muscle spindle afferents. Units could be reliably recorded for several days, permitting comparison of their activity with homonymous muscle EMG and length during a variety of normal, unrestrained movements. 2. The general observation was th...

The directional activity of whole muscles has been shown to be broadly and often multimodally tuned, raising the question of how this tuning is subserved at the level of single motor units (SMUs). Previously defined rules of SMU activation would predict that units of the same muscle (or at least of the same neuromuscular compartment) are activated homogeneously with activity peaks in the same "...

our previous studies have shown that median and ulnar nerve lesion induced calbindin (cb) immunoreactivity in some injured motoneurons in developing rats. motoneuron death induced by sciatic nerve transection in neonatal rats has been related to induction of neuronal isoform of nitric oxide synthase (nnos). the present study investigated whether expression of cb and nicotinomid adenin dinucleot...

In the locust flight system, afferents of a wing hinge mechanoreceptor, the hindwing tegula, make monosynaptic excitatory connections with motoneurons of the elevator muscles. During flight motor activity, the excitatory postsynaptic potentials (EPSPs) produced by these connections changed in amplitude with the phase of the wingbeat cycle. The largest changes occurred around the phase where ele...

REPLY: I was glad to read Dr. Volker Dietz’s recent letter to the editor (Dietz 2007) comparing his work on spasticity in humans to my studies of spasticity in the sacral spinal rat (Bennett et al. 2004). His comments highlight many of the confusions that have shrouded the study of spasticity and give me a chance to clear the air on this topic. The first confusion relates to the complexity of s...

In many animals, limb movements transition between gait patterns with increasing locomotor speed. While for tetrapod systems several well-developed models in diverse taxa (e.g., cat, mouse, salamander, turtle) have been used to study motor control of limbs and limb gaits, virtually nothing is known from fish species, including zebrafish, a well-studied model for axial motor control. Like tetrap...

We investigated changes in activities of phrenic nerve (PN) and the recurrent laryngeal nerve (RLN) during progressive hypoxia produced by administration of a mixture of 5% O2 in N2 and a mixture of 5% O2 in N2O in 8 vagotomized, paralyzed, and artificially ventilated cats anesthetized with halothane. During progressive hypoxia produced by administration of 5% O2 in N2, both PN and RLN activiti...