Summary
Effects of haloperidol on rat flexor and extensor α-motoneurones were studied in ventral roots of laminectomized rats under halothane anesthesia. The α-motoneurones were activated by tetanic stimulation of low-threshold afferents (group I and II), either of the ipsilateral peroneal nerve (“flexor α-motoneurones”) or gastrocnemius-soleus nerve (“extensor α-motoneurones”).
Haloperidol, given in the doses of 0.075, 0.15 and 0.30 mg/kg i.p. inhibited the reflex activation of flexor α-motoneurones; higher doses seemed to be more effective than lower ones. Apomorphine (2 mg/kg s.c.) partially antagonized the inhibitory action of haloperidol with some latency. Higher doses of haloperidol (0.15–0.60 mg/kg i.p.) also inhibited the reflex activation of extensor α-motoneurones; this inhibitory effect was, at least for a short time, antagonized by apomorphine (2 mg/kg s.c.).
The threshold for reflex activation both of flexor and extensor α-motoneurones was raised by haloperidol and lowered by a subsequent administration of apomorphine.
Our results suggest that akinesia and catalepsy, induced in rats by haloperidol might be, at least in part, due to a decrease in sensitivity of α-motoneurones to proprioceptive stimuli.
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Langer, J., Seeber, U., Kuschinsky, K. et al. Effect of haloperidol on reflex activation of rat α-motoneurones. Naunyn-Schmiedeberg's Arch. Pharmacol. 308, 149–154 (1979). https://doi.org/10.1007/BF00499057
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DOI: https://doi.org/10.1007/BF00499057