Anatomical evidence of direct projections from the nucleus of the solitary tract to the hypothalamus, amygdala, and other forebrain structures in the rat

https://pure.rug.nl/ws/files/6705563/2007BrainResRevFarkas.pdf

Permanent, bilateral common carotid artery occlusion in the rat: a model for chronic cerebral hypoperfusion-related neurodegenerative diseases.

Increased plasma arginine vasopressin levels in patients with congestive heart failure.

1. OPC-31260, a benzazepine derivative, has been studied for its ability to antagonize the binding of arginine vasopressin (AVP) to receptors in rat liver (V1) and kidney (V2) plasma membranes, for antagonism of the antidiuretic action of AVP in alcohol-anaesthetized rats and for diuretic action in conscious normal rats. 2. OPC-31260 caused a competitive displacement of [3H]-AVP binding to both V1 and V2 receptors with IC50 values of 1.2 +/- 0.2 x 10(-6) M and 1.4 +/- 0.2 x 10(-8) M, respectively. 3. OPC-31260 at doses of 10 to 100 micrograms kg-1, i.v., inhibited the antidiuretic action of exogenously administered AVP in water-loaded, alcohol-anaesthetized rats in a dose-dependent manner. OPC-31260 did not exert an antidiuretic activity suggesting that it is not a partial V2 receptor agonist. 4. After oral administration at doses of 1 to 30 mg kg-1 in normal conscious rats, OPC-31260 dose-dependently increased urine flow and decreased urine osmolality. The diuretic action of OPC-31260 was characterized as aquaresis, the mode of diuretic action being different from previously known diuretic agents such as furosemide, hydrochlorothiazide and spironolactone. 5. The results indicate that OPC-31260 is a selective V2 receptor antagonist and behaves as an aquaretic agent. OPC-31260 will be a useful tool in studying the physiological role of AVP and in the treatment of various conditions characterized by water retention.

Characterization of a novel aquaretic agent, OPC-31260, as an orally effective, nonpeptide vasopressin V2 receptor antagonist.

1. With dye-filled micro-electrodes single neurones in the medulla of anaesthetized paralysed cats were identified which: (a) fired rhythmically in synchrony with or were modulated by the cardiac cycle, and which ceased firing with occlusion of the ipsilateral common carotid artery (carotid sinus baroreceptor neurones); (b) were excited by stimulation of carotid body chemoreceptors by close intra-arterial injection of lobeline into the thyroid artery (carotid body chemoreceptor neurones).

2. Twelve carotid baroreceptor neurones were identified, in thirty-three cats, nine of which were localized in the intermediate area of the nucleus of the solitary tract (NTS) within 1 mm ahead of or behind the obex; three units were located either in the parahypoglossal area or the dorsal portion of the paramedian reticular nucleus (PRN).

3. Of the twenty-one carotid chemoreceptor neurones which were identified, thirteen were localized in the NTS, three in the parahypoglossal area and four in the dorsal PRN.

4. Bilateral lesions of the paramedian reticular area of medulla destroying the PRN, abolished or reversed the depressor response to electrical stimulation of myelinated fibres of the carotid sinus nerve (CSN), attenuated the depressor response to carotid sinus stretch and augmented the pressor response to chemoreceptor stimulation by lobeline. Such lesions did not significantly alter the reflex heart rate responses.

5. Small lesions of the NTS within an area 1 mm rostral to the obex abolished all reflex blood pressure and heart rate responses to electrical stimulation of the CSN or natural stimulation of carotid baro- or chemoreceptors.

6. Baroreceptors and chemoreceptors of the CSN project both to the intermediate zone of the NTS and to more medial areas of the medulla, particularly the dorsal PRN and parahypoglossal area.

7. The PRN serves to mediate the reflex depressor, but not cardio-vagal, response from myelinated baroreceptors and buffers the pressor responses from chemoreceptors; it may serve as an important area integrating cardiovascular activity descending from forebrain, brain stem and cerebellum with baroreceptor reflexes.

8. Cardiovascular reflex responses arising from non-myelinated baroreceptors and all chemoreceptors are mediated by neurones in the intermediate area of the NTS.

The role of the solitary and paramedian reticular nuclei in mediating cardiovascular reflex responses from carotid baro- and chemoreceptors.

1. The release of neurohypophysial hormones in response to carotid occlusion and haemorrhage has been studied in anaesthetized cats. Samples of jugular venous blood were extracted with alcohol and the extracts assayed for antidiuretic and milk-ejecting activity.

2. The release of vasopressin in response to bilateral occlusion of the common carotid arteries has been confirmed in the cat; this effect was abolished when the sinus nerves were divided.

3. Using a new sensitive preparation for the assay of milk-ejecting activity in blood extracts, it has been shown that no oxytocin accompanies the release of vasopressin during carotid occlusion.

4. The independent release of vasopressin without oxytocin during haemorrhage has also been confirmed, and the role of the sinus nerves and vagi in this response investigated. Bilateral division of either nerve reduced the response, but the vagus appeared to be of greater importance than the sinus nerve.

5. A reflex arc for the selective release of vasopressin has been proposed, of which the fibres of the sinus nerves and vagi form the afferent component and the neurones of the supraoptic nucleus the efferent component.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.1967.sp008266

An afferent pathway for the selective release of vasopressin in response to carotid occlusion and haemorrhage in the cat

The assay of milk-ejecting activity in the lactating rat.

1. Oxytocin and vasopressin were assayed in samples of blood collected from conscious rabbits during suckling. The milk yields were determined from the weight gain of the litters.



2. With normal milk yields (35–155 g), relatively high concentrations (31–375 μu./ml.) of oxytocin were present in the blood but vasopressin was detected in only one out of eight samples. It is concluded that the release of oxytocin by the milk-ejection reflex is essential for normal milk removal in the rabbit and that this hormone is released independently of vasopressin.



3. When the milk yield did not exceed 15 g, an amount which could be removed by passive withdrawal from the mammary gland, vasopressin was detected in four out of five blood samples but none contained a detectable concentration of oxytocin. This result can be explained by the intervention of emotional stress which is known to block the milk-ejection reflex but which acts as a stimulus for the release of vasopressin.



4. Emotional stress could inhibit the milk-ejection reflex either centrally by blocking the release of oxytocin, or peripherally by blocking the response of the mammary gland to circulating oxytocin. The absence of the hormone in blood during ineffectual suckling suggests that the block is central.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.1970.sp009039

Blood levels of oxytocin and vasopressin during suckling in the rabbit and the problem of their independent release

1. The neurones of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) were stimulated electrically in lactating cats under chloralose anaesthesia. Milk-ejection responses were used to monitor the release of oxytocin and vasopressin and both hormones were assayed in samples of blood collected during stimulation. The position of the tip of the stimulating electrode was confirmed from brain sections stained selectively for cystine-rich neurosecretory material.

2. A previous finding that stimulation of the SON in the cat releases vasopressin without oxytocin was confirmed.

3. Stimulation of the PVN caused both hormones to be released. The ratio of their concentrations in blood was variable; this suggests release from separate neurones.

4. Both hormones were also released on stimulation of the median eminence but not of the zone lying vertically between this structure and the PVN. No neurosecretory material was detected in this zone. These findings argue against the existence of a direct or medial paraventriculo-hypophysial pathway running downwards along the wall of the third ventricle.

5. Study of sections from unstimulated brains confirmed that the tractus paraventricularis cinereus of Greving which runs ventro-laterally from the PVN towards the SON, represents the principal efferent pathway for neurosecretory fibres from the PVN.

6. The results are discussed in relation to the problem of the independent release of oxytocin and vasopressin in response to physiological stimulation of the neurohypophysis.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.1971.sp009562

The hypothalamic neurosecretory pathways for the release of oxytocin and vasopressin in the cat

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1476-5381.1967.tb00419.x

Barbara J. Clark

Papers

An afferent pathway for the selective release of vasopressin in response to carotid occlusion and haemorrhage in the cat

The assay of milk-ejecting activity in the lactating rat.

Blood levels of oxytocin and vasopressin during suckling in the rabbit and the problem of their independent release

The hypothalamic neurosecretory pathways for the release of oxytocin and vasopressin in the cat

The mechanism of the inhibitory action of adrenaline on the mammary gland