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Hypothalamic-evoked effects in cat nucleus tractus solitarius facilitating chemoreceptor reflexes
L Silva-Carvalho1, M S Dawid-Milner, G E Goldsmith
1Department of Physiology, Royal Free Hospital School of Medicine, London.
Experimental Physiology
|May 1, 1993
Summary
Investigating neuronal pathways in cats, this study found distinct responses in the nucleus tractus solitarius (NTS) to inputs from the carotid sinus nerve (SN) and hypothalamic defence area (HDA). Neuronal activity differentiated between baroreceptor and chemoreceptor activation.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
Background:
- The nucleus tractus solitarius (NTS) integrates cardiovascular and autonomic information.
- The hypothalamic defence area (HDA) influences autonomic responses.
- Understanding NTS neuronal connectivity is crucial for autonomic regulation.
Purpose of the Study:
- To identify and characterize NTS neurons receiving inputs from the carotid sinus nerve (SN) and HDA in anesthetized cats.
- To investigate the functional roles of these inputs in cardiovascular reflex control.
Main Methods:
- Intracellular recordings were performed in the NTS of anesthetized cats.
- Electrical stimulation of the SN and HDA was used to evoke neuronal responses.
- Neuronal responses were analyzed in relation to baroreceptor and chemoreceptor activation.
Main Results:
- Of 44 SN-stimulated neurons, 32% showed HDA-evoked inhibitory postsynaptic potentials (IPSPs), responding only to baroreceptor activation.
- 11% showed HDA-evoked excitatory postsynaptic potentials (EPSPs), responding only to chemoreceptor activation.
- Three neurons exhibited short-latency HDA inputs, suggesting direct monosynaptic connections.
Conclusions:
- NTS neurons receiving HDA input exhibit distinct response patterns related to baroreceptor and chemoreceptor inputs.
- These findings highlight the role of the HDA in modulating NTS activity and cardiovascular reflexes.
- Direct monosynaptic HDA inputs to NTS neurons were suggested.