Thalamic reticular nucleus (TRN) neuronal subtypes and response to formalin induced nociception. (A) Distribution of the three TRN neuronal subtypes recorded within the TRN (left). Red, blue and green dots represent, typical, atypical and non-burst TRN neurons, respectively. Sample of burst firing patterns of typical and atypical TRN neurons and spiking pattern of a non-burst TRN neuron are shown in right. (B) Behavioral nociceptive responses before and after subcutaneous injection of formalin (5%, 10 μl) in the left paw pad (n = 7 mice). (C) Neuronal activities of before and after formalin injection for three different TRN neuronal sub-types: Atypical (n = 14 neurons, 5 mice), Typical (n = 10 neurons, 5 mice) and Non-burst (n = 14 neurons, 6 mice). One-way analysis of variance (ANOVA) with Games Howell post hoc was used to compare firing rate differences between neuronal subtypes at each time segment. Significance was determined at *P < 0.05. (D) Tonic and burst spike firing rate changes before and after formalin for atypical and typical TRN neurons (same neurons as in C). Two-tailed t-test was used to compare means at each time segment. Significance was determined at *P < 0.05. (C,D) All data points are Mean ± SEM. Repeated measures ANOVA was used to test for within group firing rate changes over time after formalin injection and all groups had significant changes over time. (E) Relative changes in the ratio of tonic and burst spikes over time for atypical (left) and typical (right) TRN neuronal type. Abbreviations: A, anterior; P, posterior; D, dorsal; V, ventral; L, lateral; M, medial.