The differential effect with time of neuropeptides on the proliferative responses of murine Peyer's patch and splenic lymphocytes
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The neuropeptides substance P (SP), somatostatin (SOM), and vasoactive intestinal peptide (VIP) have been shown to modulate lymphocyte DNA, RNA, and immunoglobulin synthesis. We have previously shown that SP enhances while SOM and VIP inhibit proliferation of murine splenic and Peyer's patch lymphocytes when cells were cultured with concanavalin A and neuropeptides for 72 h. Here we show that the effect of neuropeptides, in particular SP, is dependent on the amount of time that lymphocytes are incubated with NP. We found that SOM and VIP always inhibited cell proliferation for incubation times of 2 to 72 h. In contrast when cells were exposed to SP for 24 h or less, there was inhibition of [3H]thymidine uptake by both Peyer's patches and splenic lymphocytes. Significant enhancement in DNA synthesis by lymphocytes from both organs was only seen when cells were incubated with SP for the whole 72 h. We believe that our data may explain some of the conflicting reports regarding the effects of neuropeptides on cell proliferation.
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