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Thermoafferent signal processing in rats: an electrophysiological analysis of midbrain influences on thermoresponsive neurons in the ventrobasal thalamus

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Abstract

The influence of electrical midbrain stimulation on thalamic cells which respond to scrotal skin warming with steep increases in firing rate was studied in anaesthetized rats. Square-wave stimuli of 200 μs duration and 30–250 μA intensity at 15 Hz were applied in trains lasting about 1 min.

At low scrotal temperatures stimulation of the nucleus raphe dorsalis, the adjacent central grey or the median raphe nucleus was nearly always followed by a rise in thalamic activity. Inhibition occurred only in 4 of 75 experiments. Often midbrain stimulation caused neuronal responses similar to those following scrotal warming. Single stimulation experiments and the combination of electrical stimulation and electrolytic lesions indicated local interactions between excitatory and inhibitory neuronal networks in midbrain. Poststimulus latencies revealed polysynaptic midbrain/thalamic connections. Direct projections with no more than a few synaptic interruptions were seen in about 10% of the experiments.

It is concluded that medial midbrain neurons influence the transmission of peripheral thermal information to the specific thalamus and contribute to the typical switching form of thalamic responses to scrotal warming.

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References

  1. Azmitia EC, Segal M (1978) An autoradiographic analysis of the differential ascending projections of the dorsal and median raphe nuclei in the rat. J Comp Neurol 179:641–668

  2. Baraban JM, Aghajanian GK (1980) Suppression of firing activity of 5-HT neurons in the dorsal raphe by alpha-adrenoceptor antagonists. Neuropharmacology 19:355–363

  3. Baraban JM, Aghajanian GK (1981) Noradrenergic innervation of serotonergic neurons in the dorsal raphe: demonstration by electron microscopic autoradiography. Brain Res 204:1–11

  4. Barone FC, Wayner MJ, Tsai WH, deCoronado IZ (1981) Effects of periaqueductal gray stimulation on diencephalic neural activity. Brain Res Bull 7:195–207

  5. Bobillier P, Seguin S, Petitjean F, Salvert D, Touret M, Jouvet M (1976) The raphe nuclei of the cat brainstem: a topographical atlas of their efferent projections as revealed by autoradiography. Brain Res 113:449–486

  6. Bowsher D (1961) The reticular formation and ascending reticular system: anatomical considerations. Br J Anaesth 33:174–182

  7. Bowsher D (1975) Diencephalic projections from the midbrain reticular formation. Brain Res 95:211–220

  8. Brück K, Hinckel P (1980) Thermoregulatory noradrenergic and serotonergic pathways to hypothalamic units. J Physiol (Lond) 304:193–202

  9. Gottschlich KW, Schingnitz G, Werner J (1981a) Responses of thalamic neurons to thermal stimulation before and after lesioning the nucleus raphe dorsalis in the rat. Pflügers Arch 389 (Suppl):R 38

  10. Gottschlich KW, Werner J, Schingnitz G (1981b) Responses of thalamic warm cells to electrical midbrain stimulation. Pflügers Arch 391 (Suppl):R 45

  11. Gottschlich KW, Werner J, Schingnitz G (1982) Influence of the nucleus raphe centralis on thermoafferent signal transmission to the rat's thalamus. Pflügers Arch 319 (Suppl):R 37

  12. Hellon RF, Misra NK (1973) Neurones in the ventrobasal complex of the rat thalamus responding to scrotal skin temperature changes. J Physiol (Lond) 232:389–399

  13. Hellon RF, Taylor DCM (1982) An analysis of a thermal afferent pathway in the rat. J Physiol (Lond) 326:319–328

  14. Jahns R (1976) Different projections of cutaneous thermal inputs to single units of the midbrain raphe nuclei. Brain Res 101:355–361

  15. Moore RY (1980) The reticular formation: monoamine neuron system. In: Hobson JA, Brazier MAB (eds) The reticular formation revisited. Raven Press, New York, pp 67–81

  16. Pellegrino LJ, Cushman AJ (1967) A stereotaxic atlas of the rat brain. Meredith Publ Comp, New York

  17. Pfister C, Danner H (1980) Fluorescenzhistochemische und neurohistologische Untersuchungen am Nucleus raphe dorsalis der Ratte. Acta Histochem 66:253–261

  18. Schingnitz G (1981) Neuronal responses in the rat's thalamus to scrotal heating. Exp Brain Res 43:419–421

  19. Schingnitz G, Werner J (1980a) Responses of thalamic neurons to thermal stimulation of the limbs, scrotum and tongue in the rat. J Therm Biol 5:53–61

  20. Schingnitz G, Werner J (1983) Thalamic neurons in the rat responding to thermal and nocuous stimulation at various sites. J Therm Biol 8:23–25

  21. Takagi H, Senba E, Shiosaka S, Sakanaka M, Inagaki S, Takatsuki K, Tohyama M (1981) Ascending and cerebellar non-serotonergic projections from the nucleus raphe magnus of the rat. Brain Res 206:161–165

  22. Taylor DCM (1979) The effect of spinal cord lesions on the temperature-responsive neurones in the ventrobasal thalamus of the rat. J Physiol (Lond) 292:21P

  23. Taylor DCM (1982) The effects of nucleus raphe magnus lesions on an ascending thermal pathway in the rat. J Physiol (Lond) 326:309–318

  24. Wang RY, Aghajanian GK (1977) Antidromically identified serotonergic neurons in the rat midbrain raphe: evidence for collateral inhibition. Brain Res 132:186–193

  25. Werner J, Schingnitz G (1981) Correlations between neuronal responses in different nuclei of the thermoafferent system. In: Szelényi Z, Székely M (eds) Advances in physiological sciences. Académiai Kiadó, Budapest; Pergamon Press, Oxford, pp 97–99

  26. Werner J, Schingnitz G, Hensel H (1981) Influence of cold adaptation on the activity of thermoresponsive neurons in thalamus and midbrain of the rat. Pflügers Arch 391:327–330

  27. Wessendorf MW, Proudfit HK, Anderson EG (1981) The identification of serotonergic neurons in the nucleus raphe magnus by conduction velocity. Brain Res 214:168–173

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Author information

Correspondence to J. Werner.

Additional information

This work was supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich No. 114 ‘BIONACH’

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Gottschlich, K.W., Werner, J. & Schingnitz, G. Thermoafferent signal processing in rats: an electrophysiological analysis of midbrain influences on thermoresponsive neurons in the ventrobasal thalamus. Pflugers Arch. 401, 91–96 (1984). https://doi.org/10.1007/BF00581538

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Key words

  • Midbrain raphe nuclei
  • Thalamus
  • Thermoresponsive neurons
  • Thermoregulation
  • Scrotal thermal afferents
  • Rats