Biomaterial Database

Oxytocin release following osmotic activation of oxytocin neurones in the paraventricular and supraoptic nuclei. 1978

M J Brimble, and R E Dyball, and M L Forsling

1. Recordings were made from a total of 35 antidromically identified neurones in the paraventricular (PV) and supraoptic (SO) nuclei of urethane-anaesthetized lactating rats. During recording plasma osmotic pressure was raised by 12 m-osmole/kg by injection of hypertonic solutions of NaCl, LiCl, or mannitol.2. Nine PV neurones (mean firing rate 4.2 +/- 1.0 (S.E.) spikes/sec) were classified as oxytocin cells because they gave a burst of activity before reflex milk-ejections. None of these showed a bursting (phasic) firing pattern. Ten PV neurones (mean firing rate 1.8 +/- 0.2 spikes/sec) fired phasically either before or after injection of hypertonic NaCl and were classified as vasopressin cells. The remaining six PV cells (mean firing rate 1.6 +/- 0.9 spikes/sec) showed no bursts of firing related to milk ejection and did not fire phasically.3. Increasing plasma osmotic pressure by injection of hypertonic NaCl increased the mean firing rate of PV oxytocin cells to 7.0 +/- 1.0 spikes/sec. Vasopressin cells in the PV nucleus were much less responsive and the mean firing rate after injection was 2.9 +/- 0.4 spikes/sec. The third group of PV neurones was unresponsive.4. Plasma oxytocin concentration (determined by radioimmunoassay) increased from 2.1 +/- 0.3 muu./ml. in the control period to 10.9 +/- 2.8 muu./ml. 30 min after I.P. injection of 1 ml. 1.5 M-NaCl and to 14.8 +/- 2.8 muu./ml. following injection of a second 1 ml. 1.5 M-NaCl.5. The responses of oxytocin and vasopressin neurones in the SO nucleus to an increase in plasma osmotic pressure following injections of hypertonic solutions of LiCl or mannitol were similar to those observed when plasma osmotic pressure was raised by NaCl.6. It may be concluded that both oxytocin and vasopressin cells in the neurohypophysical system are responsive to the osmotic pressure of the blood plasma rather than to Na(+) or Cl(-) concentration, that osmotic activation of oxytocin cells releases sufficient oxytocin to increase its plasma concentration, and that there may be a functional difference between the SO and PV nuclei.

UI	MeSH Term	Description	Entries
D006982	Hypertonic Solutions	Solutions that have a greater osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid.	Hypertonic Solution,Solution, Hypertonic,Solutions, Hypertonic
D007031	Hypothalamus	Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.	Lamina Terminalis,Preoptico-Hypothalamic Area,Area, Preoptico-Hypothalamic,Areas, Preoptico-Hypothalamic,Preoptico Hypothalamic Area,Preoptico-Hypothalamic Areas
D008353	Mannitol	A diuretic and renal diagnostic aid related to sorbitol. It has little significant energy value as it is largely eliminated from the body before any metabolism can take place. It can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function and has been used for determination of glomerular filtration rate. Mannitol is also commonly used as a research tool in cell biological studies, usually to control osmolarity.	(L)-Mannitol,Osmitrol,Osmofundin
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D009997	Osmotic Pressure	The pressure required to prevent the passage of solvent through a semipermeable membrane that separates a pure solvent from a solution of the solvent and solute or that separates different concentrations of a solution. It is proportional to the osmolality of the solution.	Osmotic Shock,Hypertonic Shock,Hypertonic Stress,Hypotonic Shock,Hypotonic Stress,Osmotic Stress,Hypertonic Shocks,Hypertonic Stresses,Hypotonic Shocks,Hypotonic Stresses,Osmotic Pressures,Osmotic Shocks,Osmotic Stresses,Pressure, Osmotic,Pressures, Osmotic,Shock, Hypertonic,Shock, Hypotonic,Shock, Osmotic,Shocks, Hypertonic,Shocks, Hypotonic,Shocks, Osmotic,Stress, Hypertonic,Stress, Hypotonic,Stress, Osmotic,Stresses, Hypertonic,Stresses, Hypotonic,Stresses, Osmotic
D010121	Oxytocin	A nonapeptide hormone released from the neurohypophysis (PITUITARY GLAND, POSTERIOR). It differs from VASOPRESSIN by two amino acids at residues 3 and 8. Oxytocin acts on SMOOTH MUSCLE CELLS, such as causing UTERINE CONTRACTIONS and MILK EJECTION.	Ocytocin,Pitocin,Syntocinon
D010286	Paraventricular Hypothalamic Nucleus	Nucleus in the anterior part of the HYPOTHALAMUS.	Hypothalamic Paraventricular Nucleus,Paraventricular Nucleus,Hypothalamic Nucleus, Paraventricular,Nucleus, Hypothalamic Paraventricular,Nucleus, Paraventricular,Nucleus, Paraventricular Hypothalamic,Paraventricular Nucleus, Hypothalamic
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D005260	Female		Females
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential