Fig. 4

Effect of inhibiting the NRM on NTG-evoked TNC neuronal firing. a Representative recordings of neuronal firing in the trigeminal nucleus caudalis (TNC) evoked by infusing nitroglycerin (NTG) in four experimental groups. b Graph comparing the pattern of TNC neuronal firing evoked by infusing NTG in four experimental groups. In control rats, infusing NTG activated the firing of TNC neurons throughout the period of infusion (closed squares, solid line). The firing rate was increased in control rats with muscimol microinjection (closed squares, dash line; p = 0.002 compared with saline microinjection). Chronic treatment with acetaminophen increased the NTG-evoked neuronal firing in the TNC (open circles, solid line; p = 0.050, ANOVA for repeated measures). The effect of microinjection of muscimol into the NRM on increasing the TNC neuronal firing was not observed in rats that received chronic acetaminophen treatment (open circles, dashed line; p = 0.923 compared with saline microinjected acetaminophen-treated rats)