Pii: S0306-4522(00)00179-2
نویسندگان
چکیده
ÐLocomotor stimulation in the perifornical hypothalamus produces a transient facilitation of subsequent locomotion, a priming effect, such that stepping to a second train of stimulation occurs with a shorter latency of onset and increased amplitude. Neurons responsible for the initiation of this facilitated stepping presumably respond to locomotor stimulation with a similar priming effect, i.e. either a shorter latency or a larger change in activity rate. This study used anesthetized rats (urethane, 800 mg/ kg) to compare brainstem regions in terms of the relative rates of occurrence of single neurons that showed both speci®c responses to locomotor stimulation and also priming effects. Speci®c responses were characterized by a progressive increase in activity prior to the ®rst step (a Type I pattern). In that they co-varied in time with the increased probability of stepping onset, Type I responses were more speci®c than Type II responses, which peaked early in the stimulation train several seconds before the onset of stepping. Regions with high proportions of neurons showing Type I responses and priming effects included the anterior dorsal tegmentum lateral to the central gray, the oral pontine reticular nucleus and the medial gigantocellular nucleus. Few Type I neurons showed a modulation of activity related to the step cycle. Type I primed neurons were uncommon in the cuneiform and the pedunculopontine regions, but neurons showing other patterns (decreases and antidromic responses) were relatively prevalent there. The ventral tegmental area was generally unresponsive. The results indicate that stepping elicited by perifornical stimulation in the anesthetized rat is mediated by circuits that differ at midbrain levels from the circuits implicated in other types of locomotion. Two regions, the anterior dorsal tegmentum and the oral pontine reticular nucleus, warrant further attention to determine their possible roles in the initiation of locomotion. q 2000 IBRO. Published by Elsevier Science Ltd. All rights reserved.
منابع مشابه
Pii: S0306-4522(00)00005-1
The present study was performed in rats with experimentally induced mononeuropathy after left common sciatic nerve ligation. The hindpaw withdrawal latencies to thermal and mechanical stimulation increased significantly after intra-periaqueductal grey injection of 2 or 3 nmol, but not 1 nmol of galanin in rats with mononeuropathy. Intraperitoneal administration of 4.5 mg/kg morphine induced sig...
متن کاملPii: S0306-4522(99)00179-7
We describe the immunocytochemical distribution of adenosine A1 receptors in the rat hippocampus. Adenosine A1 receptor-like immunoreactivity was seen on the cell soma and dendrites of pyramidal cells and the cell soma and proximal part of dendrites of granule cells, but not on glial cells. Developmentally, adenosine A1 receptor-like immunoreactivity was diffuse on postnatal day 7 and increased...
متن کاملPii: S0306-4522(00)00129-9
Here we report that the extended surround outside the classical receptive center (hereafter called the extended surround) of most retinal ganglion cells in the cat exhibit significant orientation bias to grating stimuli, and that the center and the extended surround show different orientation biases at different spatial frequencies. As a result, some retinal ganglion cells possess a complex rec...
متن کاملPii: S0306-4522(00)00258-x
The hippocampus has long been considered critical for spatial learning and navigation. Recent theoretical models of the rodent and primate hippocampus consider spatial processing a special case of a more general memory function. These non-spatial theories of hippocampus differ from navigational theories with respect to the role of self-motion representations. The present study presents evidence...
متن کاملPii: S0306-4522(00)00089-0
We tested the hypothesis that heterogeneity in the frequency of miniature synaptic activity reflects differences in the number of vesicles present in presynaptic terminals. Using imaging techniques, we measured dendritic miniature synaptic calcium transients attributed to the spontaneous release of single transmitter quanta. Following imaging, the identified neurons were processed for serial tr...
متن کامل