Glyoxylic acid-induced monoamine fluorescence (GIF) was used to map the distribution of catecholamine-containing cell bodies and terminals in the rat nucleus tractus solitarius (NTS) and dorsal medulla. In addition, the relative vascularity of the NTS was quantified by examination of tissue perfused with Pontamine sky blue. The GIF-reactive cell bodies within the NTS complex were caudal to the rostral pole of the area postrema and are therefore considered to be the A2 cell body group as defined by Dahlström and Fuxe. The A2 cell body group was composed of 900 (890 +/- 43, n = 3) small to medium sized neurons (15-25 micron diameter) located on the dorsal and lateral edges of the dorsal motor nucleus of the vagus. GIF terminal density was found to be most dense in the medial portion of the NTS as compared to the lateral or midline portions of the NTS, dorsal motor nucleus of the vagus, or hypoglossal nucleus. Quantitative blood vessel analysis revealed that the NTS is significantly less vascularized than the surrounding nucleus gracilius, central gray, or dorsal motor nucleus of the vagus. A full serial section analysis of NTS, stained either for GIF cell bodies, terminals or blood vessels, has been obtained; this detailed presentation of catecholamine-containing profiles and blood vessels in the dorsal medulla may facilitate future studies aimed at examining central control of autonomic function.