Jan 1, 1976

Cardiovascular effects of electrical stimulation of the forebrain in the fetal lamb

Pediatric Research
R L WilliamsA M Rudolph


Modified stereotaxic techniques were applied to fetal lambs during the latter third of gestation. Electrical stimulation in the region of the hypothalamus in 10 acute experiments was associated with three patterns of arterial blood pressure and heart rate changes: a pressor-tachycardia response; a pure tachycardia response (abolished by propranolol); and a pure bradycardia response (abolished by atropine). The pressor-tachycardia response was examined in detail in 13 chronic preparations (115-135 days of gestation at operation). The systolic arterial blood pressure increase was never greater than 35 mm Hg and was probably blunted by the large noninnervated placental circulation. This pressure increase was abolished by phentolamine and was thus mediated by stimulation of alpha-adrenergic receptors. The initial tachycardia was prevented by propranolol and was due to beta-adrenergic stimulation. The tachycardia was followed in a few seconds by a bradycardia, abolished by atropine and possibly a vagal baroreflex. The pressor-tachycardia response was accentuated in two lambs who were delivered spontaneously and were studied after birth. These studies indicate that a suprabulbar neural framework exists in the fetal lamb for influenci...Continue Reading

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Mentioned in this Paper

Stereotaxic Techniques
Diastolic Blood Pressure
Organum Vasculosum Laminae Terminalis
Dall Sheep
Electric Stimulation Technique
Pulse Rate
Adrenergic beta-Antagonists

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