Mk. Herbert et al., Histamine excites groups III and IV afferents from the cat knee joint depending on their resting activity, NEUROSCI L, 305(2), 2001, pp. 95-98
The effect of histamine on the sensory activity of primary afferents was st
udied in normal a nd acutely inflamed cat knee joints. A subpopulation of g
roups III and IV articular afferents could be activated by close-arterial b
olus injections of histamine: units with a high resting activity (about 100
/min) were particular sensitive to histamine and were excited even by 3.3 f
g histamine. The lower the resting discharges of groups III and IV units bo
th from normal and acutely inflamed joints, the higher the dose of histamin
e (up to 3.3 or 33 mug) necessary to excite the nerve fibres. Thirty-seven
of 39 units without any resting activity were completely insensitive to his
tamine. In contrast to its clear excitatory effect, histamine caused only m
inor changes in the responses to joint movements. Movement-evoked activity
remained unchanged in 22 of 28 units, 1 unit was sensitized and 5 units sho
wed reduced activity after histamine (3.3 mug). The present results support
the notion that histamine may participate in the mediation of pain from in
jured or inflamed tissue. It is remarkable that histamine has a profound ex
citatory action on a proportion of both groups III and IV articular afferen
ts without changing their sensitivity to joint movements. (C) 2001 Elsevier
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