In the rat, both the activation of peripheral baroreceptors as well as electrical stimulation in the diagonal band of Broca depress the excitability of vasopressin (VP)-secreting neurons in the hypothalamic supraoptic nucleus via GABA$ sb{ rm A}$ receptors. Baroreceptor activation alters the firing of neurons in the diagonal band consistent with a role as a central relay by which baroreceptor activation arrests the activity of supraoptic VP neurons. Neurons in the adjacent median preoptic nucleus (MnPO) also receive baroreceptor-derived input. Anatomical tracing techniques indicate that MnPO neurons project directly to the supraoptic nucleus whereas diagonal band neurons project to the lateral hypothalamic area adjacent to the supraoptic nucleus where they are proposed to contact GABAergic interneurons. This study evaluates the contribution of the diagonal band and MnPO to the central pathway(s) conveying baroreceptor-derived information to supraoptic VP neurons in the rat, using in vivo extracellular electrophysiology combined with neurotoxic (ibotenic acid) lesions. Stimulation in the MnPO inhibited the majority of supraoptic neurons via GBA$ sb{ rm A}$ receptors. Selective destruction of neuronal somata in MnPO failed to alter baroreceptor-induced inhibition of supraoptic VP neurons. By comparison, lesions in the diagonal band of Broca, or lateral hypothalamus, significantly reduced the number of baroresponsive VP neurons. Moreover, lesions in the lateral hypothalamus attenuated diagonal band of Broca-, but not MnPO-evoked inhibition of supraoptic VP neurons. Thus, neurons in the diagonal band, through their connections to GABAergic interneurons located in the lateral hypothalamus, are considered to relay baroreceptor input to supraoptic VP neurons. While stimulation of MnPO inhibits supraoptic neurons via GABA$ sb{ rm A}$ receptors, this innervation does not appear to convey baroreceptor-derived information to the supraoptic nucleus.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.39394 |
| Date | January 1992 |
| Creators | Nissen, Ralph |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001305395, proquestno: NN80337, Theses scanned by UMI/ProQuest. |
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