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Cardiovascular input to hypothalamic neurosecretory neurons.
L P Renaud1, J H Jhamandas, R Buijs
1Neurosciences Unit, Montreal General Hospital, Quebec Canada.
Brain Research Bulletin
|June 1, 1988
Summary
Baroreceptor reflexes inhibit vasopressin release via GABAergic neurons in the diagonal band of Broca. Chemoreceptors and angiotensin II, however, excite vasopressin and oxytocin release.
Area of Science:
- Neuroendocrinology
- Cardiovascular Regulation
Background:
- Magnocellular neurosecretory cells (MNCs) in the hypothalamus regulate vasopressin and oxytocin release.
- Arterial baroreceptors play a crucial role in cardiovascular homeostasis by influencing MNC activity.
Purpose of the Study:
- To investigate the neural pathways and mechanisms by which baroreceptor activation influences vasopressin-secreting MNCs.
- To identify neuronal populations involved in the central regulation of vasopressin and oxytocin secretion.
Main Methods:
- In vivo extracellular recordings from rat supraoptic and paraventricular MNCs.
- Electrical stimulation of the diagonal band of Broca (DBB).
- Intracellular recordings in perfused hypothalamic explants.
- Pharmacological manipulations using bicuculline.
Main Results:
- Drug-induced hypertension activated DBB neurons projecting to the supraoptic nucleus.
- DBB stimulation selectively inhibited vasopressin-secreting MNCs via GABAergic transmission.
- Baroreceptor-induced inhibition of MNCs was blocked by bicuculline, suggesting GABA involvement.
- Chemoreceptor activation and angiotensin II increased MNC activity, indicating excitatory inputs.
Conclusions:
- Baroreflex inhibition of vasopressin secretion involves GABAergic neurons in the DBB and local interneurons.
- Excitatory inputs from chemoreceptors (via A1 noradrenergic cells) and angiotensin II (via subfornical organ) modulate vasopressin and oxytocin release.