The effects of electrical stimulation in the nuclei locus coeruleus (LC) and raphe magnus (NRM) were examined on the background and/or evoked discharge of neurones in the spinal dorsal horn of anaesthetized cats. These were qualitatively, and in most cases quantitatively similar, in their action on multireceptive neurones. In these neurones an inhibitory action on the discharge evoked by noxious cutaneous stimuli or by activation of A delta and C fibres was most prominent although in some neurones (22%) an initial excitation lasting up to 100 ms preceded the inhibition which could last up to 1 s. Excitation alone was observed in only 3% of multireceptive neurones. Electrical stimulation also produced an inhibitory action on the discharge of low threshold mechanoreceptive neurones (80%). In four of ten multireceptive neurones examined in detail, LC stimulation produced a selective inhibitory action on the discharge evoked by noxious cutaneous stimuli. In the remaining six multireceptive neurones it was partially selective against noxious as compared with non-noxious inputs. The inhibitory action was also more pronounced on the discharge evoked by activity in A delta and C fibres than fast conducting afferents. The inhibitory action evoked by electrical stimulation in LC on nociceptive transmission in the spinal cord is suggested to play a part in mediating analgesia from LC.

No abstract

We have previously reported that electrical stimulation in LC or NRM when tested on the activity of a multireceptive neurone in the spinal cord produced similar inhibitory actions. The present study aimed to define the pathways that mediate this descending inhibitory action in the spinal cord by pharmacological means and by making surgical lesions in the spinal cord or NRM. Attempts to differentiate pathways pharmacologically did not succeed since the i.v. administration of the 5-HT antagonists, methysergide and cinnanserin failed to antagonise descending inhibition evoked from either NRM or LC. Lesions involving a part or whole of the ipsilateral ventral quadrant reduced the inhibition produced from LC to a greater extent than that from NRM in 24 multireceptive neurones. In seven of these neurones stimulation in LC was without any effect after the lesion. In 23 multireceptive neurones recorded after making lesions that spared the ipsilateral ventral quadrant the effects of LC stimulation were unchanged. NRM effectiveness was reduced by an ipsilateral dorsolateral funiculus (DLF) lesion but required a bilateral DLF lesion for an almost complete abolition. Similar results were obtained when the effect of the various lesions were studied on the dorsal root potentials (DRPs) generated from LC or NRM. Lesions in the midline raphe complex, that included NRM, did not block the inhibitory action of LC stimulation. The inhibition produced from both these nuclei was additive whereas excitation was not. We conclude that LC actions in the spinal cord are mediated primarily through a pathway in the ipsilateral ventral quadrant whereas those from NRM are mediated through bilateral projections in DLF. Furthermore, although NRM plays no part in mediating LC actions and separate and independent pathways mediate their spinal action yet these apparently independent pathways have plenty of scope for interaction in the dorsal horn of the spinal cord itself.

An analysis of the brain weight of 196 rhesus monkeys and lateral X-rays of 91 more was made to determine and correct the effect of growth and development on stereotaxic variability. A comparison of body weight to brain weight shows that the brain grows rapidly initially in a linear relationship with body weight and can increase in weight even into adulthood, with a significant amount of variability found throughout its development. The examination of the cranial base and stereotaxic reference points indicates that the brain rotates during growth in a forward and downward direction in relation to the stereotaxic planes. The distance between the anterior clinoid process and AP-0 shows an increase of little variability from linearity during growth. This distance can be used to correct for the anterior-posterior plane found in standard stereotaxic atlases. The flattening out of the cranial base results in a horizontal plane readjustment during growth. A horizontal correction can be made by measuring the distance between the base of the pituitary fossa and H-10 plane.

Deficits in reciprocal inhibition likely contribute to excessive antagonist muscle cocontraction during voluntary movements of individuals with cerebral palsy. This study examined neural contributions to reciprocal inhibition of the soleus motoneurons of individuals with spastic, diplegic cerebral palsy and nondisabled individuals during various levels of voluntary tibialis anterior contraction. A condition-test H-reflex paradigm examined short- and long-latency contributions to reciprocal inhibition of soleus neural pools during changing levels of voluntary tibialis anterior contraction. Electrically induced short- and long-latency inhibition was similar between healthy, neurologically intact control subjects and subjects with cerebral palsy during rest. With increasing levels of tibialis anterior contraction, control subjects experienced increasing levels of soleus motoneuron inhibition, especially of long-latency inhibitory responses. In contrast, there was no evidence of modulation of short- or long-latency inhibition with increasing levels of tibialis anterior contraction among subjects with cerebral palsy. Deficits in long-latency (presynaptic) inhibition appear to contribute prominently to voluntary movement impairment of individuals with cerebral palsy. ( J Child Neurol 2006;21:240—246).