BRADYKININ AND MUSCLE STRETCH ALTER CONTRALATERAL CAT NECK MUSCLE-SPINDLE OUTPUT

The objective of this study was to investigate the activity of primary and secondary muscle spindle afferents (MSAs) in neck muscles, when t he contralateral splenius or trapezius muscles were (1) exposed to i.m . injection of bradykinin (BK) (6-86 mu g/ml), (2) stretched, (3) stre tched during exposure to BK or (4) stretched after exposure to BK. It was found that injection of BK, muscle stretch and the combination of the two stimuli significantly excited primary and secondary MSAs via r eflex effects onto static fusimotor neurones. BK, alone, and in combin ation with muscle stretch, induced more frequent, potent and long last ing effects as compared to muscle stretch. The effects of muscle stret ch was significantly increased after exposure of BK, indicating that s tretch-sensitive nerve-endings within neck muscles are sensitised by B K. The results are discussed in relation to the disturbances in motor co-ordination and proprioception found in patients suffering from chro nic muscle pain in the cervical region. (C) 1998 Elsevier Science Irel and Ltd. All rights reserved.