Anatomical and functional connections between the locus coeruleus and the nucleus tractus solitarius in neonatal rats

Abstract

This study was designed to investigate brain connections among chemosensitive areas in newborn rats. Rhodamine beads were injected unilaterally into the locus coeruleus (LC) or into the caudal part of the nucleus tractus solitarius (cNTS) in Sprague-Dawley rat pups (P7–P10). Rhodamine-labeled neurons were patched in brainstem slices to study their electrophysiological responses to hypercapnia and to determine if chemosensitive neurons are communicating between LC and cNTS regions. After 7–10 days, retrograde labeling was observed in numerous areas of the brainstem, including many chemosensitive regions, such as the contralateral LC, cNTS and medullary raphe. Whole-cell patch clamp was done in cNTS. In 4 of 5 retrogradely-labeled cNTS neurons that projected to the LC, firing rate increased in response to hypercapnic acidosis (15% CO2), even in synaptic blockade medium (high Mg2+/low Ca2+). In contrast, 2 of 3 retrogradely-labeled LC neurons that projected to cNTS had reduced firing rate in response to hypercapnic acidosis, both in the presence and absence of synaptic blockade medium. Extensive anatomical connections among chemosensitive brainstem regions in newborn rats were found and at least for the LC and cNTS, the connections involve some CO2-sensitive neurons. Such anatomical and functional coupling suggests a complex central respiratory control network, such as seen in adult rats, is already largely present in neonatal rats by at least day P7–P10. Since the NTS and the LC play a major role in memory consolidation, our results may also contribute to the understanding of the development of memory consolidation.

Differential Ascending Projections From the Male Rat Caudal Nucleus of the Tractus Solitarius: An Interface Between Local Microcircuits and Global Macrocircuits

“…Discussions of the possible functional significance of brain studies customarily reference electrophysiological or pharmacological articles related to specific anatomical sites or connections. For example, recent literatures have highlighted chemistry of NTS-PVH and NTS-LC connections (Affleck et al, 2012 ), central and peripheral chemoreception mechanism involving several brainstem regions such as NTS, LC, respiration-related areas and raphe (Kumar and Prabhakar, 2012 ; Nattie and Li, 2012 ; Guyenet, 2014 ; Lopes et al, 2016 ), and food intake/energy expenditure, appetite control by cholecystokinin concerned with NTS-PVH projection (Rinaman, 2010 ; D’Agostino et al, 2016 ). However, this is not the case in the present study, as the focus is not analytical or reductionist but rather a gestalt or holistic view of homeostatic control of the whole body to describe a possible underlying network system.…”

Astrocyte glycogen and lactate: New insights into learning and memory mechanisms

“…Statistical significance was assessed by twoway ANOVA followed by Bonferroni's post hoc tests compared to vehicle (**p < 0.01; ***p < 0.001; n 5 7-8/group) ALBERINI ET AL. | 1251 Summers, 2010;Lopes et al, 2016;Sara, 2009;Sara, Vankov, & Herve, 1994).…”

Brainstem Nuclei Associated with Mediating Apnea-Induced Respiratory Motor Plasticity

“…Having shown that noradrenergic LC cell activity is required for LTF expression, we next wanted to identify a mechanism by which recurrent apneas recruit and activate LC cells. Because vagal feedback is required for apnea-induced LTF 4 and because vagal afferents terminate in the NTS 11 and project to and modulate LC activity 24 , 25 , we hypothesized that the NTS is required for triggering apnea-induced LTF. Therefore, we pharmacologically inactivated cells in the NTS by bilaterally injecting lidocaine into the left and right NTS before repeatedly occluding the airway.…”