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K M Spyer

Publications and source records attributed to K M Spyer.

At least 145 records · Page 8Linked to original sources
PubMed1972

Baroreceptor sensitive neurones in the anterior hypothalamus of the cat.

1. The activity of 372 neurones, located within or close to the hypothalamic depressor area, was recorded on raising the pressure within a vascularly isolated carotid sinus.2. When the intrasinusal pressure was raised abruptly to 200 mm Hg the activity of fifteen neurones was enhanced and of six inhibited.3. The neurones exhibiting excitation on baroreceptor afferent stimulation were broadly divisible into two groups. Nine neurones responded with a marked increase in discharge frequency, the other six responded with a ;burst-on' discharge with a minimum latency of 90 msec. Excitation in both cases was always within 500 msec of the presentation of the stimulus. No functional distinction has been drawn from these responses.4. Evidence has been obtained suggesting that the responses of both types of neurone showing excitation may be potentiated using a pulsatile rather than static stimulus.5. The role of the neurones in the integration of the carotid sinus baroreceptor reflex is discussed. It is suggested that the hypothalamic depressor area represents the rostral extension of the integrative centre for the reflex.

Action Potentials↗
PubMed1971

Participation of the anterior hypothalamus in the baroreceptor reflex.

1. On the basis of discrete electrical stimulation in the pre-optic region and anterior hypothalamus of anaesthetized cats, a depressor area has been defined, stimulation of which elicits a fall of arterial blood pressure of 30-50 mm Hg and a bradycardia of some 25%, caused by inhibition of sympathetic vasomotor tone and by vagal activation respectively. These are accompanied by a reduction in rate and depth of respiration.2. The depressor area, from which this pattern of response is elicited, lies ventral and caudal to the anterior commissure, and extends caudally in the dorsal hypothalamus, dorsal to the fornix.3. The pattern of response elicited from identified points in the depressor area was shown to be indistinguishable from that to baroreceptor afferent stimulation.4. A lesion destroying the hypothalamic depressor area bilaterally reduced the response to baroreceptor afferent stimulation. Lesions in the medullary depressor area which spared a large part of the nucleus of the tractus solitarius also reduced, but did not abolish, the baroreceptor reflex response. The two lesions combined abolished the reflex.5. It is concluded that the whole brain-stem depressor area, from the hypothalamus through the mid-brain to the medulla, constitutes a functional unit which integrates the response to baroreceptor afferent stimulation.

Animals↗