Integration in descending motor pathways controlling the forelimb in the cat 15. Comparison of the projection from excitatory C3-C4 propriospinal neurones to different species of forelimb motoneurones

Summary In the preceding report (Alstermark and Sasaki 1986) it was shown that a stimulus of 500 A applied in the lateral reticular nucleus (LRN) evokes a maximal or near monosynaptic EPSP (LRN EPSP) in forelimb motoneurones. This EPSP which is assumed to be selectively mediated by C3-C4 propriospinal neurones (PNs), was used to estimate the strength of the excitatory projection from C3-C4 PNs. A systematic comparison was made of the size and time course of the maximal LRN EPSP in various species of forelimb -motoneurones innervating shoulder, elbow, wrist and digit muscles. The LRN EPSP was evoked in all investigated species of forelimb motoneurones. When either the peak amplitude or the underlying area of the LRN EPSP was compared, a three-fold range was found with some tendency for the size to vary in the order of wrist > shoulder elbow > digit > intrinsic paw motor nuclei. Generally, a positive correlation was found in each motor nucleus between the peak amplitude of the LRN EPSP versus the monosynaptic homonymous group Ia EPSP, input resistance and afterhyperpolarization duration respectively (cf. Alstermark and Sasaki 1986). It is therefore postulated, that the LRN EPSP peak amplitude is correlated with motor unit type. Comparison of the time course of the LRN EPSPs was made by measuring the time-to-peak (T-t-p) and half-width (H-w). The finding in the preceding report that the T-t-p and H-w is longer in slow than in fast motoneurones was confirmed and extended to all the investigated motor nuclei. The hypothesis that both fast slow motoneurones receive projection from a group of fast C3-C4 PNs, while slow motoneurones receive an additional projection from a group with lower conduction velocity, can therefore be applied to all forelimb motor nuclei. In addition, it is proposed that some slow shoulder, wrist and digit motoneurones receive projection from a special subpopulation of C3-C4 PNs with very slow conduction velocity.This work was supported by the Swedish Medical Research Council (project no. 94 and 6953)     

Protein nutrition and aging.

Twenty-four female rats consisting of 6 sets of litters were used for the experiment. After weaning, rats were divided into 4 groups and fed with 10, 18, 27 and 36% casein diet. Effect of protein nutrition on aging was examined from the anthropometric and biochemical viewpoint. The difference of growth in body weight, and that of the urinary excretion of creatinine and 17-ketosteroids observed in the early period of growing disappeared by the end of growth period. From 1 year after birth, serum alkaline phosphatase activity and serum cholesterol were also measured. However, effect of protein nutrition on these parameters was not clear due to the scatter of data. The difference in diet did not affect life span in the present experiments, but the effect of the variance of litters on it seemed to be significant between the rats fed 18% casein diet and those fed 10% casein diet. Rats fed high-protein diet had a great number of lesions in the kidney and hypophysis, and often an incidence of tumors.