Neurons in the dorsal rostral pons process information about changes in venous return and in arterial pressure.

To examine pathways in the brain stem that process information from cardiovascular receptors we tested, in cats anesthetized with chloralose/urethane, 76 neurons in the locus coeruleus and locus subcoeruleus for their response to hemodynamic perturbations. The experiments were designed to define processing of information from arterial baroreceptors and from atrial receptors. We have modified the activity of baroreceptors and/or atrial receptors using partial constriction of the supradiaphragmatic inferior vena cava, with and without stabilization of arterial pressure and have modified the activity of atrial receptors directly using volume pulsation of the right atrium (+/- ml, 1 Hz, 3 min). The activity of 26 neurons increased and the activity of two neurons decreased in response to constriction of the vena cava. A quantitative analysis indicates that the behavior of these neurons is related in part to changes in arterial pressure and in part to changes in other pressures, such as atrial pressure. None of the neurons stimulated by constriction of the vena cava responded to volume pulsation of the right atrium. However, 6 of 9 responsive neurons tested responded also to contriction of the vena cava during stabilization of arterial pressure. Under this condition the neurons must be responding to changes in the activity of cardiovascular receptors other than arterial baroreceptors. The results suggest strongly that neurons in the locus coeruleus and locus subcoeruleus process information about changes in venous return and in arterial pressure. It is hypothesized that the responsive neurons may mediate changes in the release of pituitary hormones and in behavioral arousal in response to hemodynamic change.