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trigeminal nucleus were antidromically activated by LC stimulation. These results suggest that a few neurons in STN and LC may be involved in a feedback oop between locus coeruleus and s:)inal trigeminal nucleus.

Trigeminal nociceptive and non-nociceptive neurones" brain stem intranuclear projections and modulation by orofacial, periaqueductal gray and nucleus raphe magnus s t i m u l i . - J.W. Hu and B.J. Sessle, Brain Res., 170 (1979) 547--552.

This study pravides physiological evidence for direct projections from trigeminal subnucleus caudalis to more rostral subdivisions of the trigeminal brain stern sensory complex. Over 50% of neurons studied in subnucleus caudalis were antidromically activattzi from ipsilateral subnucleus oralis. A few also sent collaterals to the contr~lateral thalamus. Both nociceptive and non-nociceptive neurons contributed to this projection and both types were subject to modulating influences from periaqueductal gray and nucleus raphe magnus stimulation. In addition, the presynaptic endings of these neurons in subnucleus oralis were subject to similar modulation, as demonstrated by changes in antidromic excitability produced by conditioning stimulation. It is of interest that these descending effects are exerted both in subnucleus caudalis and at their presynaptic endings in subnucleus oralis.

PHARMACOLOGY

Bradykinin as an algesic (pain producing) substance in the p u l p . - R. Inoki, K. Matsumoto, T. Kudo, Y. Kotani and M.Oka, Naunyn-Schmiedeberg's Arch. exp. Path. Pharmak., 306 (1979) 29--36

A rat uterine smooth muscle cor,tracting substance was released into the superfusate of the dog's exposed ~anine pulp after noxious stimulation of the pulp by pricking, heat and electrical stimulation. This active substance was acid- and heat-resistant and was decomposed by carboxypeptidase B and a-chymotrypsin, but not by carboxypeptidase A and trypsin. This substance was also tested on several types of smooth muscle. Electrical activity of nerve cells in the reticular formation, which were sensitive to stimulation of the instep of the foot by pinching, was activated by the intrafemoral admin- istration of thc active substance. The algesic activity of this substance was examined in cantharidin blister base in man. This study conclusively demonstrated that the active substance of the pulp released by noxious stimulation produced pain and it was identified as bradykinin.

Reversal by naloxone of adaptatio~ of rats to noxious stimuli. -- M. Satoh, S. Kawajiri, M. Yamamoto, H. Makino and H. Takagi, Life Sci., 24 (]979) 6 8 5 - 6 9 0

Bradykinin, a potent pain-produ,~:!ng substance, injected into the common iliac artery of the rat produced flexor reflexes of the hindlimb. The bradykinin-induced response was reduced following the repetition of such