The effects of field stimulation on bovine mesenteric lymph node contractility.

In these studies isometric tension was recorded from isolated strips of bovine mesenteric lymph node capsule. The possible influence of intrinsic nerves on their contractile activity was examined using field stimulation and the pharmacology of the response was investigated. Over 75% of the tissues studied demonstrated regular spontaneous activity at a frequency of 3.9 +/- 0.2 contractions/5 min under control conditions. Field stimulation at 2.8 and 32 Hz (pulse width = 0.3 ms, nominal voltage 60 V) produced frequency-dependent increases in the rate of this spontaneous activity associated with a raised baseline tension. These responses were not diminished on repeat stimulation under control conditions. The contraction frequency response to stimulation at 8 Hz was blocked completely in the presence of 1 microM tetrodotoxin, while the increase in baseline tension was reduced by over 80%, suggesting that field stimulation was activating intrinsic nerves. The responses to stimulation (8 Hz) were also greatly reduced by 10 microM phentolamine but were unaffected by 10 microM propranolol. These experiments suggest that intrinsic nerves can modulate the contractile activity of lymph node capsule acting, at least in part, through excitatory alpha-adrenoceptors. The possible functional significance of this is discussed.