Abstract
It is crucial for animals to discriminate between palatable (safe) and aversive (toxic) tastants. The mechanisms underlying neuronal discrimination of taste stimuli remain unclear. We examined relations between taste response properties (spike counts, response duration, and coefficient of variation [CV]) and location of taste‐sensitive neurons in the pontine parabrachial nucleus (PBN). Extracellular single units’ activity in the PBN of Wistar rats was recorded using multibarrel glass micropipettes under urethane anesthesia. Forty taste‐sensitive neurons were classified as NaCl (N)‐best (n = 15), NaCl/HCl (NH)‐best (n = 14), HCl (H)‐best (n = 8), and sucrose (S)‐best (n = 3) neurons. The net response to NaCl (15.2 ± 2.3 spikes/s) among the N‐best neurons was significantly larger than that among the NH‐best (4.5 ± 0.8 spikes/s) neurons. The response duration (4.5 ± 0.2 s) of the N‐best neurons to NaCl was significantly longer than that of the NH‐best (2.2 ± 0.3 s) neurons. These differences in the spike counts and the response durations between the two neuronal types in the PBN were similar to that previously reported in the rostral nucleus of the solitary tract (rNST). The CVs in the N‐best and the NH‐best neurons were significantly smaller in the PBN than those in the rNST. Histologically, most N‐best neurons (12/13, 92%) were localized to the medial region, while NH‐best neurons (11/13, 85%) were primarily found within the brachium conjunctivum. These results suggest that NaCl‐specific taste information is transmitted by two distinct neuronal groups (N‐best and NH‐best), with different taste properties and locations within rNST to PBN tractography. Future studies on the higher order nuclei for taste could reveal more palatable and aversive taste pathways.
Highlights
Taste-topic map in the cerebral gustatory cortex (Accolla, Bathellier, Petersen, & Carleton, 2007; Chen, Gabitto, Peng, Ryba, & Zuker, 2011; Peng et al, 2015; Yamamoto, Yuyama, Kato, & Kawamura, 1985) and the rostral nucleus of the solitary tract, a first-order taste relay (Yokota, Eguchi, & Hiraba, 2014), implied topographical segregations for taste-sensitive neurons in the pontine parabrachial nucleus (PBN), a second-order taste relay
In the rostral nucleus of the solitary tract (rNST), we reported that N-best neurons could be distinguished from NaCl/HCl (NH)-best neurons based on their response properties and based on the more rostral distribution of NH-best neurons (Yokota et al, 2014)
We investigated the relationship between response properties and locations of taste-sensitive neurons in the PBN
Summary
Taste-topic map in the cerebral gustatory cortex (Accolla, Bathellier, Petersen, & Carleton, 2007; Chen, Gabitto, Peng, Ryba, & Zuker, 2011; Peng et al, 2015; Yamamoto, Yuyama, Kato, & Kawamura, 1985) and the rostral nucleus of the solitary tract (rNST), a first-order taste relay (Yokota, Eguchi, & Hiraba, 2014), implied topographical segregations for taste-sensitive neurons in the pontine parabrachial nucleus (PBN), a second-order taste relay. The PBN contains medial and lateral regions that surround the superior cerebellar peduncle, known as the brachium conjunctivum (BC) These regions are involved in multiple functions, including conveying taste information, gastrointestinal signals, respiratory cycles, and regulating cardiovascular function. Each of these functions is hypothesized to be segregated into distinct regions with some overlap in the PBN (Baird, Travers, & Travers, 2001; Cohen, 1971; Hayward & Felder, 1995; Herbert, Moga, & Saper, 1990; Karimnamazi, Travers, & Travers, 2002; Lara et al, 2002). We investigated the relationship between response properties (spike count, response duration, and coefficient of variation [CV]) and locations of taste-sensitive neurons in the PBN
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