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R G Dyer

Publications and source records attributed to R G Dyer.

At least 73 records · Page 4Linked to original sources
PubMed1976

Non-random distribution of cell types in the preoptic and anterior hypothalamic areas.

1. Single units were recorded extracellularly from the preoptic and anterior hypothalamic areas of male and female rats anaesthetized with urethane. 2. The effect of single shock stimulation of both the mediobasal hypothalamus and corticomedial amygdala upon unit activity was assessed for all cells. Neurones were designated either antidromically invaded, orthodromically excited or inhibited, or non-responsive. 3. The distribution of responses among recorded cells was analysed for two groups of neurones. In one group the intercell distance was less than 100 mum and in the second group the distance was more than 1 mm. 4. For widely separated cells the connexions with the corticomedial amygdala and mediobasal hypothalamus were distributed at random. 5. In the groups of cells clustered closely together a marked structuring of connexions was apparant. In particular, there was a significant correlation between orthodromic responses from the amygdala (P less than 0-05) and cells antidromically activated and orthodromically excited by stimulation of the mediobasal hypothalamus were frequently adjacent to one another (P less than 0-02. 6. A complimentary analysis demonstrated that cells in the ventral half of the recording zone received significantly more inhibitory inputs from both the mediobasal hypothalamus (P less than 0-001) and the corticomedial amygdala (P less than 0-02) than those situated more dorsally. 7. The data provide evidence for structuring and orderliness in hypothalamic connexions that is often not apparent from descriptions of electrophysiological experiments.

Amygdala↗
PubMed1976

Effects of ferrous ions on preoptic area neurones and luteinizing hormone secretion in the rat.

Ferrous ions (Fe2+) were applied by microiontophoresis of 29 neurones recordid from the forebrain of ten pro-oestrous rats. The spontaneous activity of 24 cells was reduced by Fe2+ and five units did not respond. No excitations were observed. Reproducible responses could not be obtained with ferric ions (Fe3+). Microinjection of 1 mul 200 mM-Fe2+ into the preoptic area of eight pro-oestrous rats produced a sharp increase in plasma LH levels. Similar treatment with saline was without effect. Rats anaesthetized with sodium pentobarbitone during the early afternoon of pro-oestrus ovulated overnight when injected with both Fe2+ and Fe3+. The experiments do not confirm the widely held belief that raised plasma LH levels following deposition of iron in the rostral hypothalamus result from increased firing of nerve cells.

Action Potentials↗
PubMed1975

Endocrine neurons.

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Action Potentials↗
PubMed1973

An electrophysiological dissection of the hypothalamic regions which regulate the pre-ovulatory secretion of luteinizing hormone in the rat.

1. Extracellular action potentials were recorded from 299 single units in the preoptic and anterior hypothalamic areas of fifty-two female rats anaesthetized with urethane. The units were categorized by their response to single biphasic pulses (ca. 1 mA; 1 msec duration) applied to the ventromedial/arcuate region of the hypothalamus.2. Experiments with five lactating rats demonstrated that the effective zone of stimulation was confined within the ventromedial/arcuate region. This observation was supported by further evidence obtained during unit recording sessions.3. Antidromic action potentials were recorded from 122 (41%) of the neurones monitored in preoptic and anterior hypothalamic areas. These Type A cells were characterized by their very slow discharge rate (median for spontaneously active units 1.2 spikes/sec) when contrasted with adjacent cells (median 3.9 spikes/sec). Orthodromic action potentials were not observed in thirty-six Type A cells. The antidromically identified neurones had an average conduction rate of 0.32 m/sec. The absolute refractory period of the soma, computed by separation of the IS and SD components of the antidromic action potentials recorded from forty-four neurones, ranged from < 3.0 to > 100 msec. With ten units it was not possible to obtain a soma dendritic (SD) wave by antidromic activation even though the initial segment (IS) wave was seen clearly and the orthodromic potentials consisted of both IS and SD waves.4. Type B cells (32% of population) were excited and/or inhibited by the ventromedial/arcuate stimulation but were not antidromically activated. This post-stimulatory change in discharge rate lasted for up to 400 msec.5. Type C cells (27% of population) showed no change in spontaneous activity after stimulation of the ventromedial arcuate area. These neurones had discharge rates similar to Type B cells.6. The previously reported prooestrous increase in firing rate, recorded from neurones in the ventral part of the preoptic/anterior hypothalamic area was restricted to cell Types B and C.

Action Potentials↗