Date of Award


Degree Type


Degree Name

Doctor of Philosophy


In this study baro- and chemoreceptor input to the amygdala was investigated with electrophysiological experiments in chloralose-anesthetized cats and with the neuroanatomical tracing method of retrograde transport of horseradish peroxidase.;Stimulation of the carotid sinus (CSN) and aortic depressor (ADN) nerves altered the firing frequency of 30% (73/241) and 20% (50/251), respectively, of single units in the central, lateral and basal nuclei of the amygdala.;Selective activation of carotid baro- and chemoreceptors altered the firing frequency of 23% (35/154) and 16% (24/154), respectively, of amygdalar units, with chemoreceptor responsive units located primarily in the dorsomedial amygdala and baroreceptor responsive units located primarily in the ventrolateral amygdala.;Retrograde transport of horseradish peroxidase demonstrated many brain sites, including the paraventricular nucleus of the hypothalamus (PVH) and the parabrachial nucleus (PB) with direct projections to the nuclei of the amygdala receiving cardiovascular input.;Stimulation of the CSN and ADN altered the firing frequency of 34% (64/189) and 24% (18/185), respectively, of PB units. Furthermore, stimulation of the amygdala and PVH antidromically and orthodromically activated PB units, of which approximately half also responded to buffer nerve stimulation.;Stimulation of the PVH elicited a response in 19% (27/140) of amygdalar units, of which 33% also responded to chemoreceptor activation while 31% (46/150) of amygdalar units responded to stimulation of the PB, of which 24% also responded to chemoreceptor activation and 4% responded to baroreceptor activation.;A model is proposed indicating that chemoreceptor input to the dorsomedial amygdala is an important component of behavioral arousal while the baroreceptor input to the ventrolateral amygdala inhibits this system. In addition, the PB plays a key role in relaying cardiovascular information to the forebrain and in receiving converging descending forebrain information and ascending cardiovascular input and then sends an integrated signal to autonomic and respiratory effectors. Finally, both the PVH and PB were demonstrated to be likely sites of relay of cardiovascular afferent information from the medulla to the amygdala.



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