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

Summary The present investigation was undertaken to study the effects of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretory system in rats.The drugs were injected intraperitoneally and into the lateral brain ventricle. The water diuresis was measured (I group). The animals were killed 45 min after intraperitoneal and 20 min after intraventricular administration of the drugs for the histological observations on the neurosecretory system and the histochemical studies of catecholamines in this area (II group).The antidiuretic effect of adrenaline and acetylcholine was established. The antidiuresis was more remarkable following intraventricular treatment.There was no direct relationship between the amount of neurosecretory substance and ADH activity in the posterior pituitary in the short term experiment after intraperitoneal administration of these drugs.The rapid release of ADH from the posterior pituitary was accompanied with a remarkable output of neurosecretory substance from the neurosecretory cell bodies into the axons and these effects were considerable after intraventricular introduction of the drugs. Some neurosecretory cells in the state of the initial hyperfunction were observed. In the posterior pituitary the initial mobilisation of the neurosecretory material from the neurosecretory terminals following intraventricular introduction of the drugs was observed.The supraoptic nucleus seems to be more sensitive to acetylcholine and the paraventricular nucleus to adrenaline treatment.The significant vasodilatation in the posterior pituitary and in the area of the supraoptic nucleus following intraventricular acetylcholine introduction was established.According to the data described it is possible to expect the existence of control of the hypothalamic neurosecretory activity by means of adrenergic and cholinergic structures.I am very obliged to Prof. W. Bargmann for his stimulating interest in this Study. I am grateful to Dr. G. Leontieva and Dr. V. Govyrin for the possibility to use the fluorescence catecholamine method, to Dr. E. Zeimal and Prof. M. Michelson for using the method for intraventricular injections.     

The development of connections of the magnocellular hypothalamic nuclei with the posterior hypophyseal lobe in rat prenatal ontogeny]

The development of projections of the hypothalamic nuclei into the posterior lobe of the pituitary was studied on the fixed brain of rat fetuses from day 15 until day 19 of embryogenesis using retrograde staining with the fluorescent carbocyanine dye DiI. The formation of connections of the supraoptic and retrochiasmatic nuclei of the hypothalamus with the posterior lobe of the pituitary takes place during prenatal development on days 15 and 16-17, respectively, while only an insignificant number of the paraventricular nucleus neurons send their axons to the posterior lobe of the pituitary in rat fetuses. These facts suggest different temporal involvement of the above nuclei in formation of the hypothalamic-hypophysial neurosecretory system in rat fetuses.     

Reaction of the hypothalamo-hypophyseal system of cats to stimulation of the cervical sympathetic nerve and the afferent fibers of the vagus nerve]

Data are presented on the functional morphology of the hypothalamo-hypophysial neurosecretory system of cats in stimulation of the cervical sympathetic nerve and of the afferent fibers of the vagus. Stimulation of the sympathetic nerve selectively activated the supraoptic nucleus and caused the discharge of the neurohormones from the posterior lobe of the hypophysis, whereas its infundibular portion contained much neurosecretory material. In response to the stimulation of the vagus all the portions of the neurohypophysis were released of the Gomori-positive substance; both the supraoptic and the paraventricular nucleus were activated.     

Response of rat hypothalamic perinuclear supraoptic neurons to stimulating the pituitary stalk and hippocampus

Orthodromically activated neurons (OAN) are found in the hypothalamic supraoptic area under pituitary stalk stimulation, differing in their dependence on pattern of orthodromic activation and recording site. More than a half of OAN responded to stimulation of the ventral hippocampus and response was consistently excitatory initially. Some similarity was found between the pattern of response of most OAN to pituitary stalk stimulation. Aspects of hippocampal influence on OAN taking account of their location within the supraoptic nucleus area and the perinuclear zone are examined, as well as their presumed morphofunctional connections with antidromically identified neurosecretory cells.A. A. Ukhtomskii Institute of Physiology, State University, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 596–604, September–October, 1990.     

Angiotensin II in the mechanisms of hypothalamic pressor reactions

The influence of intracerebroventricular injections of the angiotensin II antagonist--saralasin on the cardiovascular reactions elicited by electrical stimulation of different structures of the hypothalamus in rabbit was studied. The saralasin in doses from 1 to 1.5 mg reduced arterial pressure by 9 +/- 0.2 mm Hg and decreased the amplitude of the hypertensive reactions elicited by electrical stimulation of the paraventricular, supraoptic, ventromedial, supramammillary nucleus of the hypothalamus, area hypothalamic anterior and lateral. It has been shown that most suppressing influence of the saralasin on amplitude of the hypertensive reactions elicited by electrical stimulation of the paraventricular (68%) and supraoptic (76%) nucleus of the hypothalamus which contain magnocellular neurosecretory neurons.     

CHANGES IN THE HYPOTHALAMO-NEUROHYPOPHYSICAL NEURO-SECRETORY MATERIALS OF RATS DURING DIFFERENT PHASES OF MORPHINE ADMINISTRATION

Abstract—

• 1 Acute morphine treatment of rats increased the concentration of neuro-secretory material in the posterior pituitary. These changes were accompanied by the presence of more neurosecretory materials in the axons of the hypothalamic supraoptic and paraventricular neurons and in the hypothalamic capillaries and sinuses. In the perikarya of the hypothalamic supraoptic and paraventricular neurons, the neurosecretory material is in a dispersed state.
• 2 Following chronic morphine treatment, neurosecretory material was almost absent from the posterior pituitary, whereas in the perikarya of the supraoptic and paraventricular neurons, congestion of neurosecretory material is observed which is accompanied by the absence of the neurosecretory material from the axons arising from the supraoptic and paraventricular nuclei and from the hypothalamic capillaries and sinuses.
• 3 During nalorphine-induced abstinence, there was sudden reappearance of the neurosecretory material in the posterior pituitary along with the appearance of neurosecretory material in the hypothalamic neurosecretory neuronal tracts, blood capillaries and sinuses together with the dispersion of the neurosecretory materials from the hypothalamic neurosecretory neurons.

     

Cholinesterase activity of the hypothalamo-hypophysial neurosecretory system in rats during the ontogenetic development

Summary The hypothalamic region and the neural lobe of rats from the 16th foetal day to adult animals have been studied for acetylcholinesterase and cholinesterase activity after Karnovsky. The attention was focused on the magnocellular nuclei-supraoptic and paraventricular, the median eminence and the neural lobe. Acetylcholinesterase activity appears in the paraventricular nucleus on the 18th foetal day, i.e. prior to that in the supraoptic nucleus. Heterochronic development and heteromorphism of paraventricular neurosecretory cells have been noticed. The median eminence shows no clear acetylcholinesterase activity. There are acetylthiocholine and butyrylthiocholine positive structures in the posterior pituitary. These structures are especially pronounced in 30–47-day rats. The cholinergic mechanism of release of neurohormones from the neural lobe is suggested. The results are discussed in functional and phylogenetic aspects.     

Quantitative histoenzymatic analysis of the hypothalamic neurosecretory system in rat ontogeny

In experiments on 6 and 16 days old rats cytophotometric studies have been made of histochemical reactions for succinate, lactate and glutamate dehydrogenases, alpha-glycerophosphate dehydrogenase and glucose-6-phosphate dehydrogenase in the supraoptic nucleus, paraventricular hypothalamic nucleus and the posterior hypophysis. It was found that heterochronous development of the neurones in the supraoptic and paraventricular nuclei, as well as the development of their axons in the posterior hypothalamus depend on the rate of maturation of the enzymic systems in postnatal life. In consolidation of the unique structure of the hypothalamic neurosecretory system, the key role is played by afferent influences, succinic dehydrogenase being involved into their realization. The data obtained indicate the importance of heterochronous development of the enzymic activities in the formation of bifunctional properties of neurosecretory hypothalamic neurones and reveal the primary development of neurotransmittery function as compared to the excretory one.     

Ultrastructure of the neurosecretory cells of the anterior commissural nucleus of the hypothalamus in rats

The ultrastructure of neurosecretory cells of the anterior commissural nucleus of rat hypothalamus is similar to that of the supraoptic nucleus and of the "magnocellular" part of the paraventricular nucleus. The only difference is a less expressed granular endoplasmatic reticulum and a smaller diameter of elementary neurosecretory granules (80-150 nm in diameter). Such elementary granules are characteristic of neurosecretory terminals located in the external zone of the median eminence. It is suggested that neurosecretory cells of the anterior commissural nucleus project to this neurohemal region.     

Gomori-positive elements of the hypothalamo-hypophyseal neurosecretory system of the rat (immunohistochemical study)

Vasopressiergic and oxytocinergic cells and fibers in the hypothalamo-hypophysial neurosecretory system have been identified by means of immuno-histochemical reactions. Vasopressin-producing cells localize mainly in the ventral part of the supraoptic nucleus (SON) and in the dorsolateral part of the paraventricular nucleus (PVN). Oxytocin-producing cells predominantly concentrate in the dorsal part of the SON and in the ventromedial part of the PVN. In the central part of the posterior pituitary lobe vasopressin-containing fibers are mainly situated, and in the peripheral parts--both oxytocin- and vasopressin-containing fibers are revealed. Owing to separate localization of vasopressin- and oxytocin-producing cells in the SON and especially in the PVN, in preparations stained with paraldehyde-fuchsin after Gomori-Gabe it is possible to analyse these cells separately.     

The Clinical Physiology of Water Metabolism: Part I: The Physiologic Regulation of Arginine Vasopressin Secretion and Thirst

Water balance is tightly regulated within a tolerance of less than 1 percent by a physiologic control system located in the hypothalamus. Body water homeostasis is achieved by balancing renal and nonrenal water losses with appropriate water intake. The major stimulus to thirst is increased osmolality of body fluids as perceived by osmoreceptors in the anteroventral hypothalamus. Hypovolemia also has an important effect on thirst which is mediated by arterial baroreceptors and by the renin-angiotensin system. Renal water loss is determined by the circulating level of the antidiuretic hormone, arginine vasopressin (AVP). AVP is synthesized in specialized neurosecretory cells located in the supraoptic and paraventricular nuclei in the hypothalamus and is transported in neurosecretory granules down elongated axons to the posterior pituitary. Depolarization of the neurosecretory neurons results in the exocytosis of the granules and the release of AVP and its carrier protein (neurophysin) into the circulation. AVP is secreted in response to a wide variety of stimuli. Change in body fluid osmolality is the most potent factor affecting AVP secretion, but hypovolemia, the renin-angiotensin system, hypoxia, hypercapnia, hyperthermia and pain also have important effects. Many drugs have been shown to stimulate the release of AVP as well. Small changes in plasma AVP concentration of from 0.5 to 4 μU per ml have major effects on urine osmolality and renal water handling.     

Pattern of response in neurosecretory cells of the rat hypothalamic supraoptic nucleus to subiculum stimulation under water deprivation

The effects of water deprivation were investigated in the pattern of response produced by subiculum stimulation in antidromically identified hypothalamic supraoptic neurosecretory cells of lactating rats. In dehydrated animals as compared with the controls, the percentage of neurons responding to subiculum stimulation with an inhibitory action (blockade of antidromic action potential) remained unchanged, although the proportion of differing inhibitory response did alter: numbers of cells with gradually developing inhibitory response increased significantly and fewer cells showed transitory development of inhibition. Inhibitory response emerging as depression of background spike activity showed a quantitative increase, moreover. Plasticity was found to be one distinguishing feature of afferent input from the subiculum to supraoptic nucleus neurosecretory cells and, in particular, a capacity for reorganization under water deprivation.A. A. Ukhtomskii Institute of Physiology, State University, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 243–249, March–April, 1990.     

The role of the basal hypothalamus in the regulation of reproductive behavior in the lizard, Anolis carolinensis: lesion studies

Bilateral radiofrequency lesions in the anterior and posterior basal hypothalamus decreased courtship and agonistic behaviors in both intact, sexually active, and castrated, androgen treated male Anolis carolinensis. Intact males receiving lesions in the anterior basal hypothalamus had atrophied testes, aspermia, and decreased epithelial cell height of the renal sex segment. Lesions of the posterior basal hypothalamus had no effect on testicular activity or the development of accessory organs. All animals demonstrating behavioral changes had lesion destruction in the ventromedial nucleus and the accompanying periventricular system. It is concluded that the basal hypothalamus in male A. carolinensis is involved both in the regulation of reproductive behavior and pituitary function.     

Maturation of the hypothalamo-neurohypophysial system

Summary Sections of the hypothalamus, median eminence and pituitary from fetal and neonatal rats were examined with the immunoperoxidase staining technique and light microscopy. Purified antisera raised against vasopressin and oxytocin, and antisera cross-reactive with rat neurophysin were used to localize these antigens in the hypothalamo-neurohypophysial system (HNS). Neurophysin was detected throughout the HNS of the 18-day fetal rat. Vasopressin was present in the hypothalamus and pituitary of the 19-day fetus, and in the median eminence of the 4-day neonate. Oxytocin was not detected in the pituitary until 1–2 days after birth, in the hypothalamus after 4 days, and in the median eminence after 8 days. During the first days after birth the supraoptic nucleus was more mature than the paraventricular nucleus. The HNS did not approach maturity until at least 7 days after birth. The relative maturity of the supraoptic nucleus compared with the paraventricular nucleus, and the detection of vasopressin before oxytocin are evidence for the one-neuron-one-hormone theory. The data do not exclude the possibility that the fetal hypothalamo-neurohypophysial system, and perhaps the fetal hormone, vasotocin, affect the initiation and course of parturition.This work was financed by the Medical Research Council of New Zealand     

Immunocytochemical identification of an LHRH-producing system originating in the preoptic nucleus of the duck

Summary A fluorescent technique applying specific LHRH and vasotocin antisera was used for the immunocytochemical localization of the respective neurosecretory systems in the hypothalamus of gonadectomized, testosteronetreated and/or serotonin injected male domestic ducks. An immunoreactive (IR) LHRH-producing system, with perikarya located in the preoptic nucleus, could be traced through the ventral hypothalamus down to the external layer of the rostral and caudal ME, in close vicinity to the hypophysial portal system. An IR-vasotocin system originating in the paraventricular and supraoptic nuclei ran through the ventral hypothalamus, but terminated in (i) the external layer of the rostral ME, and (ii) in the posterior lobe of the hypophysis.Dr. B. Kerdelhué, Laboratoire des Hormones polypeptidiques du CNRS, F-91190 Gif-sur-Yvette, France     

Relationship of the central ACTH-immunoreactive opiocortin system to the median eminence and the pituitary gland of the rat

Summary By immunocytochemical methods, the present study describes ACTH-immunoreactive fibers in the pituitary stalk and neural lobe. This opiocortin-hypothalamo-neural lobe projection arises in a bed nucleus of perikarya in the basal hypothalamus, follows supraoptico-hypophyseal fibers in the zona interna of the median eminence, and distributes throughout the neural lobe. No ACTH-immunoreactive fibers project to the zona externa; some are present in the subependymal layer and at the lateral margins of the median eminence. Further studies must identify the role of these fibers in posterior lobe function. It remains also to be determined whether this system terminates upon primary pituitary portal capillaries and delivers opiocortin neuropeptides to the adenohypophysis.Supported by NIH Grants HD-07962, NS-15345 and AM-22029The skillful technical assistance of Donna Wilson, Nancy Dembs and Jay Hocton is thankfully acknowledged     

Functional changes in neurosecretory cells of the anterior hypothalamic nuclei after stimulation of the midbrain reticular formation

The functional activity of the neurosecretory cells in the supraoptic and paraventricular nuclei was studied in male Wistar albino rats at various intervals after electric stimulation of the midbrain reticular formation. These studies showed that such stimulation elicits higher functional activity of the neurosecretory cells in the anterior hypothalamic nuclei, characterized by increased secretory synthesis by these cells and rapid transport of the neurosecretion. These changes were most pronounced 1 h after stimulation of the reticular formation. The changes observed were unidirectional in both neurosecretory centers, but their manifestation was different: in the supraoptic nucleus the reaction was more intense but short lived, in the paraventricular it was less intense but lasted longer.A. A. Bogomolets Institute of Physiology, Academy of Sciences, Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 394–400, July–August, 1971.     

The distribution of monoamines in the hypothalamus of the Japanese quail Coturnix coturnix japonica

Summary The distribution of monoamines in the hypothalamus of the Japanese quail (Coturnix coturnix japonica) has been studied using a histochemical fluorescence technique. In the posterior hypothalamus catecholamine-containing nerve fibres are localised in the nucleus tuberis and nucleus hypothalamicus posterior medialis and are linked by fluorescent tracts running in the stratum cellulare internum. Further tracts may be traced from the nucleus tuberis around the base of the third ventricle to the sub-ependymal layer of the median eminence, where they then appear to pass through the hypothalamo-hypophysial neurosecretory tract to terminate in the palisade zone on the portal vascular bed. The innervation of the palisade layer by catecholamines is sparse. The fluorescent terminals are spread evenly throughout both the anterior and posterior divisions of the median eminence. There is no monoamine innervation of the pars nervosa. The paraventricular organ has both 5-hydroxytryptamine- and catecholamine-containing cell bodies and axons may be traced into the region of the nucleus hypothalamicus posterior medialis. In the anterior hypothalamus the neurosecretory paraventricular nucleus contains many catecholamine nerve fibres and terminals. These are linked by fibre tracts to the nucleus basalis and to the nucleus hypothalamicus posterior medialis. The supraoptic nucleus is less well innervated although a dense accumulation of fibres lies in the preoptic recess. The latter is thought to give rise to long axons which pass in association with the neurosecretory tract to end in the nucleus tuberis.Supported by a Grant (AG 24/36) from The Agricultural Research Council. We are indebted to Dr. G. A. Clayton, Institute of Animal Genetics, University of Edinburgh, for supplying the birds.