Fos expression in the FoxP2 and Lmx1b neurons of the parabrachial nucleus following cardiovascular changes

Abstract

The parabrachial nucleus (PB) is a key brainstem site that receives visceral afferent inputs from the nucleus tractus solitarius, and sends efferent projections to the forebrain. Since the chemical identity of the cardiovascular‐receptive PB neurons remains largely unknown, we used a new approach to define the PB neurons on the basis of their neural lineage. Discrete subpopulations of the PB neurons in adult rats constitutively express the transcription factors Forkhead box protein2 (FoxP2), LIM homeodomain transcription factor 1 beta (Lmx1b), and in some cases, both. Fos‐activation in the PB was analyzed after sustained hypotension or hypertension in conscious rats. Hypotension and hypertension produced similar Fos‐expression patterns. Fos‐activated FoxP2 neurons were found in the dorsal lateral and external lateral PB subgroups and Fos‐activated Lmx1b neurons were concentrated in the medial and external lateral PB regions. Lmx1b activated neurons were present in the dorsomedial PB. Kölliker‐Fuse neurons express both FoxP2 and Lmx1b, and only a few were Fos‐activated after cardiovascular changes. In conclusion, five PB subdivisions (dorsal lateral, dorsal medial, external lateral, and medial, Kölliker‐Fuse) receive cardiovascular information. These data clearly implicate specific PB populations in cardiovascular regulation. Supported by NIH Grants HL‐25449, NS057105, and DA0017371.