In a long-term neuromuscular blocked (NMB) rat preparation, tetanic stimulation of the aortic depressor nerve (ADN) enhanced the A-fiber evoked responses (ERs) in the cardiovascular region of the nucleus of the solitary tract (dmNTS). The potentiation persisted for at least several hours, and may be a mechanism for adaptive adjustment of the gain of the baroreflex, with functional implications for blood pressure regulation. Using a capacitance electrode, we selectively stimulated A-fibers, and acquired a stable 10 hour "A-fiber only" ER baseline at the dmNTS. Following baseline, an A+C-fiber activating tetanus was applied to the ADN. The tetanus consisted of 1000 "high current" pulses (10 trains (300 µs, 100 Hz, 1 s), with inter-train interval of 9 s). A 10 hour "A-fiber only" post-tetanic test phase repeated the stimulus pattern of the baseline. Fourteen tetanus experiments were done in 12 rats. Compared with the baseline before tetanus, the A-fiber ER magnitudes of post-tetanus hours were larger (F(13, 247) = 3.407, p < .001); additionally, the 10 hours post tetanus magnitude slopes were more positive than during 10 hours before tetanus (df = 13; t = -3.47; P < 0.005); thus an ADN A+C-fiber activating tetanus produced increases in the magnitude of the A-fiber ERs in the dmNTS that persisted for several hours. In an additional rat, application of an NMDA receptor antagonist, prior to the tetanus, blocked the potentiation effect. The stimulus protocols; magnitude and duration of the effect; and pharmacology resemble associative long term potentiation (LTP).