CONVERGENT INFLUENCE OF THE CENTRAL NUCLEUS OF THE AMYGDALA AND THE PARAVENTRICULAR HYPOTHALAMIC NUCLEUS UPON BRAIN-STEM AUTONOMIC NEURONS AS REVEALED BY C-FOS EXPRESSION AND ANATOMICAL TRACING

Combinations of anatomical tracing with detection of Fos (the protein product of the immediate early gene c-fos) consequent to the stimulati on of the central nucleus of the amygdala were used to explore the pos sibility that the hypothalamic paraventricular nucleus participates in the activation of brainstem neurons in the nucleus of the solitary tr act and ventrolateral medulla, After injections of the anterograde tra cer Phaseolus vulgaris leucoagglutinin in the paraventricular nucleus, labeled fibers and varicosities were found to impinge on catecholamin ergic and non-catecholaminergic Fos-positive neurons in the brainstem, After injections of a retrograde tracer in the nucleus of the solitar y tract or ventrolateral medulla, we observed that some of the Fos-pos itive neurons within the parvocellular paraventricular nucleus that pr oject to the brainstem were catecholaminergic or oxytocinergic. The re sults indicate that direct and indirect inputs from the amygdala may i nfluence the activity of autonomic neurons in the brainstem, The parav entricular nucleus, via its direct projections onto catecholaminergic and non-catecholaminergic neurons, may participate in activation of br ainstem neurons, Activated catecholaminergic and oxytocinergic parvoce llular neurons in the paraventricular nucleus may be involved in the t ransmission of autonomic signals from the amygdala toward the brainste m. (C) 1995 Wiley-Liss, Inc.