A restructuring off hypothalamic synapses is associated with motherhood.
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Biomedical subjects
J D Hatton
Publications and source records attributed to J D Hatton.
Spontaneous activity in perfused hypothalamic slices: dependence on calcium content of perfusate.
We have established a totally-immersed, perfused slice preparation of the hypothalamus which is amenable for electrophysiological and pharmacological studies. The amount and pattern of spontaneous activity in the paraventricular nucleus (PVN) is markedly influenced by varying the amount of Ca++ in the oxygenated physiological medium which continuously perfuses the slice over both upper and lower surfaces. Ca++ concentrations greater than 1 mM virtually abolish spontaneous activity, although the neurons discharge in response to advance of the electrode and are activated by addition of glutamate to the perfusate. However, in a perfusing medium containing 0.75 mM Ca++, most cells display 1-7 Hz spontaneous activity for up to 10 h; some cells display phasic activity similar to that attributed to vasopressin neurons in vivo. Electrical stimulation peripheral to the PVN elicits antidromic potentials in some PVN neurons, sometimes followed by a post-activation depression of activity typical of recurrent inhibition. Under appropriate perfusion conditions, therefore, the hypothalamic slice preparation displays characteristics of the in vivo hypothalamus.
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The distribution of orthogonal arrays and their relationship to intercellular junctions in neuroglia of the freeze-fractured hypothalamo-neurohypophysial system.
Using freeze-fracture techniques, we have investigated membrane specializations of the glia associated with the hypothalamo-neurohypophysial system of the rat. In the paraventricular (PVN) and supraoptic (SON) nuclei, astrocytes in areas of high neuronal density (i.e., magnocellular regions) display orthogonal arrays of 6--7 nm particles solely near gap junctions, while astrocytes in areas of lower neuronal density (i.e., parvocellular regions), contain additional arrays in membranes not displaying gap junctions. Arrays are especially numerous on astrocytic perivascular end-feet in both nuclei and in the laminations of the pial-glial limitans ventral to the SON. Ependymal cells near the PVN show arrays both on their lateral surfaces (displaying gap junctions) and on their apical surfaces (facing the CSF). Tight junctions are not noted on astrocytes or ependymal cells, but are noted on both the somas and myelin lamellae of oligodendroglia. Both of these latter membranes occasionally contain gap junctions as well; however, orthogonal arrays are never noted on oligodendroglia. The plasma membranes of pituicytes in the neurohypophysis display gap junctions, complex junctions, and tight junctions. Orthogonal arrays are noted near the first two of these, but not near the last. Arrays in the neutral lobe appear most dense on membranes adjacent to subpial or perivascular spaces. Pituicyte membranes containing orthogonal arrays appear infrequently near the neural stalk, increasing towards the distal end of the neural lobe. The distribution of orthogonal arrays in this system, as well as in other systems in which they have been noted, suggests a polarization of membrane activity.
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Morphine and opioid peptides reduce paraventricular neuronal activity: studies on the rat hypothalamic slice preparation.
Extracellular discharges of neurons in the paraventricular nucleus (PVN) were recorded from slices of rat hypothalamus in vitro. PVN neurons (n = 14) were identified by the criteria of (i) phasic activity patterns and (ii) antidromic invasion from the neurohypophysial tract. Neurons not displaying either of these features were considered unidentified with respect to physiological function (n = 85). The majority of unidentified neurons responded to bath application of morphine (1 microM), [D-Ala2,Met5]enkephalin (1 microM) or beta-endorphin (0.01-1 microM) with a prompt, reversible, dose-related reduction in spike discharge frequency. Naloxone (1 microM) antagonized the opioid-induced depressions in some, but not all, cases. At the concentrations tested, no tachyphylaxis to the effects of the opioids was observed. The opioid effects on putative neurohypophysial neurons were less pronounced; while 2 were depressed, the remaining 12 displayed no change in frequency or pattern of discharge to micromolar concentrations of morphine, [D-Ala2,Met5]enkephalin, or beta-endorphin. Our results indicate that opioids depress neuronal activity in the rat PVN via an interaction with a specific opiate receptor but that this effect is more pronounced on unidentified neurons than on putative neurohypophysial neurons in the slice.
Animals↗
Behavioral effects of aluminum ingestion on animal and human subjects.
Abnormally high brain aluminum concentrations have been detected in hemodialysis patients who died of an unexplained encephalopathy. As a result, this study was undertaken to examine whether the ingestion of aluminum produces behavioral aberrations in non-dialysed human subjects and rats with ostensibly normal renal function. Rats were fed AlCl3 by intubation in varying doses, and tests measuring learning ability, visual temporal acuity, motor coordination and activity were administered. It was found that orally ingested aluminum is absorbed by rats and deposited in the brain. High brain aluminum levels are associated with rapid general activity, decreased ability to maintain roto-rod activity, and increased sensitivity to flicker. Behavioral tests were also given to elderly human subjects and performance correlated with serum aluminum level. High serum levels of aluminum in elderly humans are associated with impaired visuo-motor coordination, poor long-term memory, and increased sensitivity to flicker.
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