The effect of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretion in the rat

Journal of Endocrinology

1972

Measurements of the blood volume of the neural and anterior lobes of the pituitaries of rats using 51Cr-labelled erythrocytes indicated that all stimuli examined which released neurohypophysial hormones also led to a significant increase in neural lobe blood volume. The blood volume of the anterior lobe was not altered by any of these stimuli.Experiments with parasympathetic blocking drugs indicated that this mechanism involved cholinergic pathways, a conclusion which was supported by the results of experiments with parasympathomimetic drugs. Sympathetic blockers and sympathomimetic drugs produced no appreciable effects on the blood volume responses.It is concluded that vasodilation occurs in the neural lobe of the rat associated with stimuli which are known to release neurohypophysial hormones and that this vasodilation involves cholinergic mechanisms but that these pathways may not be identical with those responsible for hormone release.

Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 97%

Variations in the Blood Volume of the Neural and Anterior Lobes of the Pituitary of the Rat Associated With Neurohypophysial Hormone-Releasing Stimuli

Sooriyamoorthy¹,

Journal of Endocrinology

1972

“…Observations with the electron microscope of small nerve endings, usually in close proximity to neurohypophysial blood vessels, some of which correspond with the ultrastructural appearance of cholinergic (others with adrenergic) nerve endings, may indicate a purely vascular function for acetylcholine in the neurohypophysis (Lederis, 1967a, b;Lederis & Livingston, 1966). Such a view is supported by the observation that administration of acetylcholine in rats causes a vasodilatation in the neurohypophysis (Konstantinova, 1967 …”

Section: Discussionsupporting

confidence: 57%

Acetylcholine and related enzymes in the neural lobe and anterior hypothalamus of the rabbit

Lederis¹,

The Journal of Physiology

1969

SUMMARY1. Acetylcholine (ACh), cholinesterases and choline acetyltransferase (choline acetylase) were estimated in the neural lobe and hypothalamus of the adult male rabbit. Acetylcholine was also estimated in the neural lobes and hypothalami of some other mammals.2. Acetylcholine-like activity was measured by bio-assay using the leech dorsal muscle preparation.3. Characterization experiments indicated that about 90 % of the activity measured was due to acetylcholine.4. Mean acetylcholine content in the neural lobe of the rabbit, after extraction with perchloric acid, was 4-38 + 0-98,g/g fresh tissue, and 4-87 + 1-53 /tg/g in the hypothalamus.5. Acetylcholine was also found to be present, in comparable concentrations, in the neural lobe of man and in the neural lobes and hypothalami of ox, rat and hedgehog.6. Acetylcholinesterase, present in the neural lobe and hypothalamus of the rabbit, hydrolysed 1-74 + 0-11 It-moles of substrate/min/g and 3-78 + 0*60 It-moles substrate/min/g fresh tissue respectively.

“…In spite of absence of direct experimental evidence, it cannot be excluded that neurohypophysial blood flow may change in relation to changing rates of hormone release. Since vasodilatation has been shown to occur in the neural lobe after intraperitoneal as well as intraventricular administration of ACh (Konstantinova, 1967), an increased blood flow through the neurohypophysis (facilitated by ACh) may be postulated to coincide with, or follow, the arrival of a hormone-releasing stimulus and enhance the early arrival of vasopressin or oxytocin at the target organ. Experiments are in progress to test this hypothesis.…”

Section: Discussionmentioning

confidence: 99%

Neuronal and subcellular localization of acetylcholine in the posterior pituitary of the rabbit

Lederis¹,

The Journal of Physiology

1970

SUMMARY1. Acetylcholine and neurohypophysial hormones were measured in subcellular fractions of rabbit neurohypophysis.2. Differential anddensity gradient centrifugation, followed by bio-assay and electron microscopy were used to separate and characterize the subcellular particles, or isolated nerve endings.3. Acetylcholine in the rabbit neurohypophysis was found to occur in small vesicles of about 40 nm diameter which had similar characteristics to the synaptic vesicles from central nervous tissue.4. Examination of intact nerve endings isolated from the rabbit neurohypophysis indicated that at least some acetylcholine and neurohypophysial hormones occurred in separate nerve endings.