Neuroscicmc Lt,llos. 140 11992) 37 41 .c, 1992 Elsevier Scientific Publishers Ireland Ltd. All rights reserved 0304-3940/92/$ 05.00
37
NSL 08657
Brainstem influences on biceps reflex activity and muscle tone in the anaesthetized rat R J . W . J~ch, A. S c h a a f s m a a n d J.D. v a n Willigen D~7~arlment O/Neurohio/o alic area of dynamic control) and tile red nucleus, l h e MesADC systems control 2" v~hercas flae rubrospinal system controls ?% 76 alld '~ motoueurone activity [1,2]. Activation of these system,~ or part of these systems therefore might be explanatory for the observed effects on our experiments. However, the question remains whether the observed increase in biceps activity after stimulation of the M L R is the result of an excitatory action on c~ motoneurones or to an enhanced fusimotor drive, From the time expanded view in Fig. 2 we can see that E M G activity perfectly remained in phase with the imposed length signal and stimulus unrelated activity was not recorded. The electrical stimulation of the M L R did not increase background activity of ~ motoneurones but reinforced the response to muscle vibration. We explain the observed increased response to muscle vibration at least partly being due to an enhanced drive of the fusimotor system. The same explanation can be given for the enhanced responses to muscle stretch. However, a direct facilitation of spinal cc motoneurones cannot be excluded. This can be derived from the experiment as presented in Fig. 1. This figure shows that at stimulus offswitch only a partial drop in E M G activity occurs and often a sustained lower level of E M G activity remained for several tens of seconds. This sustained activity can be explained by a shift in excitability of ¢z motoneurones. Similarly, a shift in excitability can be seen in the experiments where reversed ramp and holds were applied to the muscle (Fig. 4). Here the muscle already displayed a certain amount of tonic activity duc to the imposed pre-stretch. In the control situation this tonic activity immediately disappears in response to muscle release whereas during electrical stimulation, despite the drop in spindle output, tonic E M G activity is sustained. These observations suggest that ct motoneurones display a shift in excitability upon electrical stimulation which resembles the one reported in other studies recording motoneurone membrane potentials [6, 7, 13].
1 Appelberg, B., Selective central control of dynamic gamma motoneurones utilized for the functional classification of gamma cells. In A. Taylor and A. Prochazka (Eds.), Muscle Receptor and Movement, Macmillan, London, 1981. 2 Appelberg, B., Hulliger, M., Johansson, H. and Soika, P., An intracellular study of rubrospinal and rubro-bulbospinal control oflumbar ?'-motoneurones,Acta Physiol. Scan., 116 (1982) 377 386. 3 Barnes, C.D., d'Ascanio, R, Pompeiano, O. and Stampacchia, G.. Cholinergic brainstem sites lor gain control of vestibutospinal reflexes in cats, Brain Res., 435 (1988) 32-41. 4 Chan, J.Y.H., Fung, S.J., Chan, S.H.H. and Barnes. C D . Facilitation of lumbar monosynaptic reflexesby locus coeraleus in the rat. Brain Res., 369(1986) 103-11)9
41 5 Coles. S.K., lies. J.F. and Nicolopoulos-Stournaras, S.. The mesencephalic centre controlling locomotion in the rat, Neuroscience. 28 (1989} 149 157. 6 Conway, B.A.. ttultborn. H., Kiehn. O. and Mintz, I., Plateau polentials in alpha-motoneurones induced by intravenous injection of L-DOPA and clonidine in the spinal cat, J. Physiol., 405 (1988) 369 384. 7 Crone, C., Hultborn, H., Kiehn, O., Mazieres, L. and Wigstr6m, H., Maintained changes in motoneuronal excitability by short-lasting synaptic inputs in the dccerebrate cat, J. Physiol.. 405 (1988) 321 343. 8 Footc, S.L., Bloom, F.E. and Aston-Jones. G., Nucleus locus coeraleus: new evidence of anatomical and physiological specificity, F'hysiol. Re,,,.. 63 (1983) 844 914. 9 Fung. S.J., Pompeiano, O. and Barnes, C.D., Suppression of the recurrent inhibitory pathway in lumbar cord segments during locus coeruleus stmmlalion in cats. Brain Rcs., 402 (1987) 351 354. 10 Garcia-Rill, E. and Skinner. R.D., The mesencephalic locomotor region. 1. Activation of a medullary projection site, Brain Res., 411 (1987) 1 12. I1 Gareia-Rill, E. and Skinner, R.D., The mesencephalie locomotor region. 11. Projections to reticulospinal neurons, Brain Res., 411 (1987) 13 20.
12 Holstege. G., Descending motor pathway and the spinal motor system: limbic and non-limbic components, Progr. Brain Res.. 87 (1991) 307 419. 13 Hounsgaard, J., Hultborn, H., Jespersen, B. and Kiehn, O., Bistability of alpha-motoneurones in the decerebrate cat and in the acute spinal cat after intravenous 5-hydroxy-tryptophan, J. Physiol.. 405 (1988) 345 367. 14 Jones, B.E. and Beaudet, A., Distribution of acetylcholme and catecholaminc neurons in the cat brainstem: a choline acetyhransferase and tyrosine hydroxylase imnmnohisiochcmical sludy. ,I. ('omp. Neurol., 261 (1987i 15-32. 15 Nygren, L.G. and OIsen, L., A new m~0or projection from locus coeruleus: the main source of noradrenergic nerve terminals in the ventral and dorsal columns of the spinal cord. Brain Res., 132 (1977) 85 93. 16 Paxinos. G. and Watson, C., The Rat Brain in Stereotaxic Coordinates, 2nd edn., Academic Press. New York, 1986. 17 Skinner. R.D. and Garcia-Rill. E., The mesencephalic locomotor region (MLR) in the rai, Brain Rcs., 323 (1984) 385 389. 18 Walberg, F.. Paths descending from the brainstem An overview, In B. Sj61und and A. BjOrklund (Eds.), Brain Stem Control of Spiroll Mechanisms, Elsevier, 1982. pp. 1 27.
37
NSL 08657
Brainstem influences on biceps reflex activity and muscle tone in the anaesthetized rat R J . W . J~ch, A. S c h a a f s m a a n d J.D. v a n Willigen D~7~arlment O/Neurohio/o alic area of dynamic control) and tile red nucleus, l h e MesADC systems control 2" v~hercas flae rubrospinal system controls ?% 76 alld '~ motoueurone activity [1,2]. Activation of these system,~ or part of these systems therefore might be explanatory for the observed effects on our experiments. However, the question remains whether the observed increase in biceps activity after stimulation of the M L R is the result of an excitatory action on c~ motoneurones or to an enhanced fusimotor drive, From the time expanded view in Fig. 2 we can see that E M G activity perfectly remained in phase with the imposed length signal and stimulus unrelated activity was not recorded. The electrical stimulation of the M L R did not increase background activity of ~ motoneurones but reinforced the response to muscle vibration. We explain the observed increased response to muscle vibration at least partly being due to an enhanced drive of the fusimotor system. The same explanation can be given for the enhanced responses to muscle stretch. However, a direct facilitation of spinal cc motoneurones cannot be excluded. This can be derived from the experiment as presented in Fig. 1. This figure shows that at stimulus offswitch only a partial drop in E M G activity occurs and often a sustained lower level of E M G activity remained for several tens of seconds. This sustained activity can be explained by a shift in excitability of ¢z motoneurones. Similarly, a shift in excitability can be seen in the experiments where reversed ramp and holds were applied to the muscle (Fig. 4). Here the muscle already displayed a certain amount of tonic activity duc to the imposed pre-stretch. In the control situation this tonic activity immediately disappears in response to muscle release whereas during electrical stimulation, despite the drop in spindle output, tonic E M G activity is sustained. These observations suggest that ct motoneurones display a shift in excitability upon electrical stimulation which resembles the one reported in other studies recording motoneurone membrane potentials [6, 7, 13].
1 Appelberg, B., Selective central control of dynamic gamma motoneurones utilized for the functional classification of gamma cells. In A. Taylor and A. Prochazka (Eds.), Muscle Receptor and Movement, Macmillan, London, 1981. 2 Appelberg, B., Hulliger, M., Johansson, H. and Soika, P., An intracellular study of rubrospinal and rubro-bulbospinal control oflumbar ?'-motoneurones,Acta Physiol. Scan., 116 (1982) 377 386. 3 Barnes, C.D., d'Ascanio, R, Pompeiano, O. and Stampacchia, G.. Cholinergic brainstem sites lor gain control of vestibutospinal reflexes in cats, Brain Res., 435 (1988) 32-41. 4 Chan, J.Y.H., Fung, S.J., Chan, S.H.H. and Barnes. C D . Facilitation of lumbar monosynaptic reflexesby locus coeraleus in the rat. Brain Res., 369(1986) 103-11)9
41 5 Coles. S.K., lies. J.F. and Nicolopoulos-Stournaras, S.. The mesencephalic centre controlling locomotion in the rat, Neuroscience. 28 (1989} 149 157. 6 Conway, B.A.. ttultborn. H., Kiehn. O. and Mintz, I., Plateau polentials in alpha-motoneurones induced by intravenous injection of L-DOPA and clonidine in the spinal cat, J. Physiol., 405 (1988) 369 384. 7 Crone, C., Hultborn, H., Kiehn, O., Mazieres, L. and Wigstr6m, H., Maintained changes in motoneuronal excitability by short-lasting synaptic inputs in the dccerebrate cat, J. Physiol.. 405 (1988) 321 343. 8 Footc, S.L., Bloom, F.E. and Aston-Jones. G., Nucleus locus coeraleus: new evidence of anatomical and physiological specificity, F'hysiol. Re,,,.. 63 (1983) 844 914. 9 Fung. S.J., Pompeiano, O. and Barnes, C.D., Suppression of the recurrent inhibitory pathway in lumbar cord segments during locus coeruleus stmmlalion in cats. Brain Rcs., 402 (1987) 351 354. 10 Garcia-Rill, E. and Skinner. R.D., The mesencephalic locomotor region. 1. Activation of a medullary projection site, Brain Res., 411 (1987) 1 12. I1 Gareia-Rill, E. and Skinner, R.D., The mesencephalie locomotor region. 11. Projections to reticulospinal neurons, Brain Res., 411 (1987) 13 20.
12 Holstege. G., Descending motor pathway and the spinal motor system: limbic and non-limbic components, Progr. Brain Res.. 87 (1991) 307 419. 13 Hounsgaard, J., Hultborn, H., Jespersen, B. and Kiehn, O., Bistability of alpha-motoneurones in the decerebrate cat and in the acute spinal cat after intravenous 5-hydroxy-tryptophan, J. Physiol.. 405 (1988) 345 367. 14 Jones, B.E. and Beaudet, A., Distribution of acetylcholme and catecholaminc neurons in the cat brainstem: a choline acetyhransferase and tyrosine hydroxylase imnmnohisiochcmical sludy. ,I. ('omp. Neurol., 261 (1987i 15-32. 15 Nygren, L.G. and OIsen, L., A new m~0or projection from locus coeruleus: the main source of noradrenergic nerve terminals in the ventral and dorsal columns of the spinal cord. Brain Res., 132 (1977) 85 93. 16 Paxinos. G. and Watson, C., The Rat Brain in Stereotaxic Coordinates, 2nd edn., Academic Press. New York, 1986. 17 Skinner. R.D. and Garcia-Rill. E., The mesencephalic locomotor region (MLR) in the rai, Brain Rcs., 323 (1984) 385 389. 18 Walberg, F.. Paths descending from the brainstem An overview, In B. Sj61und and A. BjOrklund (Eds.), Brain Stem Control of Spiroll Mechanisms, Elsevier, 1982. pp. 1 27.
