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E R Greer

Publications and source records attributed to E R Greer.

13 recordsLinked to original sources
PubMed1989

Medial preoptic area oxytocin and female sexual receptivity.

Intracerebroventricular (icv) administration of the nonapeptide oxytocin (OXT) increases sexual receptivity in female rats. The medial preoptic area (MPOA) appeared to be the most sensitive brain area to the facilitative effects of OXT. Bilateral infusions of 100 ng of OXT into the MPOA significantly elevated lordosis quotients in ovariectomized (OVX), estrogen-treated rats. This dose of OXT was ineffective when infused icv or into the ventromedial hypothalamus, mesencephalic central gray, or ventral tegmental area. A 500-ng dose of OXT significantly elevated lordosis responding when infused icv, corresponding with our previous findings. Mounting by males significantly increased immunoreactive levels of OXT and decreased the number of OXT immunostaining cells in the MPOA of sexually receptive rats pretreated with estrogen and progesterone. The MPOA is a primary site of the OXT facilitation of sexual receptivity where OXT may be released during mating.

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PubMed1988

Ovarian steroids and sexual interaction alter oxytocinergic content and distribution in the basal forebrain.

The immunoreactive levels of oxytocin (OXY) were assessed by radioimmunoassay (RIA) and immunohistology after treatments with estradiol or estradiol and progesterone in ovariectomized rats that were mounted or not mounted by males. In micropunches from the medial preoptic area (MPOA) OXY immunoreactive levels increased significantly in estrogen-progesterone-treated receptive animals (mean lordosis quotient (LQ) = 82.9 +/- 4.4) that were mounted by males over levels in estrogen-treated unreceptive animals (mean LQ = 2.3 +/- 1.3). No other areas demonstrated significant changes in OXY levels across these treatments, although the paraventricular nucleus also had elevated OXY levels in receptive mounted females. In other animals, immunocytochemistry revealed that the number of oxytocinergic perikarya in the MPOA decreased in receptive animals (LQ = 86.7 +/- 4.9) that were mounted. The number of oxytocinergic perikarya per 50 microns vibratome section in the lateral subcommissural nucleus was lower in all estrogen-treated groups than in oil vehicle-treated controls. We suggest that the combination of increasing immunoreactive levels of OXY in the MPOA with decreasing numbers of oxytocinergic perikarya indicates that preoptic OXY is moved out of cell bodies, in receptive rats that are mounted by males, to a state that is more accessible to the RIA.

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PubMed1988

Cortical asymmetry--a preliminary study: neurons-glia, female-male.

Previous studies on human cortical area 39 suggested that neuron:glial ratios differed between the sexes. These findings were the inspiration for the present investigation which dealt with neuronal and glial counts in area 39 in the male and female rat cerebral cortex. Transverse, celloidin or frozen sections, were cut from male and female brains (respectively) from 90-day-old Long-Evans rats. Neurons and glia were counted on enlarged photographs of stained sections, including area 39, with 35-mm Kodak Panatomic-X film using a Zeiss photomicroscope (X400). Five-by-three-inch prints were taped together in sequence to yield a 640X enlarged "montage" of area 39. Five cell types were differentiated with reference to a standard: neurons, astrocytes, oligodendrocytes, "dark astrocytes," and unidentified glia. The data were analyzed with a two-way analysis of variance (ANOVA: five cell types by two hemispheres). Student's t test and a paired t test were used when appropriate. The neuron:glial ratios in the male rats were consistently higher than those in the females in both hemispheres. The male right side had 12% (P less than 0.05) more neurons than the left; the female had 13% (P less than 0.05) more neurons on the left than the right. Similar, but not identical, asymmetrical patterns were seen with the glial cells.

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PubMed1987

Rat cortical morphology following crowded-enriched living conditions.

This experiment studied cerebral cortical morphology in rats living in a crowded-enriched condition. Three groups of 60-day-old, male Long-Evans rats were divided accordingly: 12 rats, 3 per small cage (32 X 20 X 20 cm), standard colony condition; 12 rats in a single, large, enrichment cage with "toys" (70 X 70 X 45 cm), enriched condition; and 36 rats in a large, single, enrichment cage with "toys", crowded-enriched condition. Matched toys for the two enriched cages were changed twice a week at the time of cage cleaning. Measurements on 20-micron, transverse brain sections showed that in both the crowded-enriched and enriched groups the thickness of the medial occipital cortex increased by 4 to 6% compared with the cortex from animals in the standard colony condition. In addition, the crowded-enriched group demonstrated a 4% (P less than 0.05) increase in thickness in area 39 in the left hemisphere compared with the standard control. However, the thickness in area 39 in the crowded group was not significantly different from that of the enriched area 39. These results indicate that the cortex increases in thickness as much with "crowding" and enrichment as with enrichment alone. We hypothesize that diversion through interaction with "toys" mitigates the stress of crowded conditions.

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PubMed1987

Oxytocin and vasopressin immunoreactivity in hypothalamic and extrahypothalamic sites in late pregnant and postpartum rats.

This study examines immunoreactive levels of oxytocin (OT) and arginine-vasopressin (AVP) from acid extracts of the paraventricular nucleus (PVN), supraoptic nucleus (SON), anterior commissural nucleus (ACN) and the suprachiasmatic nucleus (SCN) as well as selected extrahypothalamic sites in pregnant or postpartum (PP) rats. Animals are sacrificed between 08.30 and 10.30 h 16 or 22 days after sperm is detected in their vaginal smears or on the morning after parturition. Peptide levels of pregnant or PP animals are compared to levels of ovariectomized (OVXed) rats sacrificed and assayed simultaneously. OT immunoreactive levels in the PVN and SON are significantly elevated in late pregnancy and PP. OT content of the ACN is elevated on day 16, but drops to control levels by day 22 of pregnancy and day 1 PP. Concomitant with the falling OT content in the ACN at the end of pregnancy, samples from the ventral septum have significantly increased OT content on day 1 PP. In extracts including the nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus (dMX) OT is also elevated on the day after parturition. AVP levels peak on the day before parturition in all hypothalamic nuclei examined. These increases are significantly greater than in OVXed controls in the PVN and SON. AVP levels in the lateral habenula are elevated both on day 16 of pregnancy and on the first day PP. From these data we conclude that nonapeptide levels are altered across late pregnancy and early postpartum in some hypothalamic synthesis sites and in certain limbic and brainstem sites. We also postulate that OT is transported out of the ACN to extrahypothalamic sites around the time of parturition.

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PubMed1986

Variations in concentration of oxytocin and vasopressin in the paraventricular nucleus of the hypothalamus during the estrous cycle in rats.

Oxytocin (OT) and arginine-8-vasopressin (AVP) were measured by radioimmunoassay in micropunched hypothalamic neurosecretory nuclei of estrous cycling female Sprague-Dawley rats. In the paraventricular nucleus (PVN): the concentration (pg/microgram protein) of OT was significantly higher in rats in diestrus than during proestrus, estrus, or metestrus, while the concentration during metestrus was significantly greater than in proestrus and estrus; the concentration of AVP was significantly lower in animals in estrus than during the other three stages; because the paraventricular OT levels dropped before proestrus, the AVP/OT ratio was significantly greater in animals in proestrus than in diestrus, metestrus, and estrus. In the supraoptic nucleus (SON) a similar trend was noted: the concentration of OT was highest during diestrus, and AVP was lowest during estrus, though neither was significantly different from other stages. Because the OT and AVP cycles in the SON were asynchronous, the ratio of AVP to OT was significantly higher in proestrus than in metestrus or diestrus and significantly greater in estrus than during diestrus. In contrast to these two areas, peptide concentrations did not vary significantly across the estrous cycle in other sites of nonapeptide synthesis, i.e. the anterior commissural nucleus (ACN) and the suprachiasmatic nuclei (SCN).

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PubMed1986

Regional cerebral cortical deficits in the immune-deficient nude mouse: a preliminary study.

This report examines the morphology of the cerebral cortex in the nude mouse (nu/nu) compared with the BALB/c(+/+). Our experiments indicated that the thickness of the lateral frontal lobe was significantly reduced (8%; P less than 0.005) in the 4-month-old, female nude mouse compared with a BALB/c mouse of like sex and age. In addition, the left hemisphere was, in general, thinner in the nude than in the BALB/c, with area 18 being significantly thinner (2%; P less than 0.005). Oligodendrocytes were less in area 18 in the nude by 25% (P less than 0.02) in contrast to the BALB/c. In some respects these results extend the work of others. In previously published experiments, we showed that the thickness of the frontal cortex from enriched and impoverished female rats (from 60 to 116 days of age) differed by 2 to 3% (P less than 0.001) and in male rats by 3 to 4% (P less than 0.001). The oligodendrocytes in area 18 in the male differed by 20% (P less than 0.02) in rats exposed to their respective enriched or impoverished environments from 25 to 105 days of age. Thus, we have shown that the frontal cortical morphology as well as the occipital cortical oligodendrocytes were altered in both immune-deficient animals and environmentally stimulated or impoverished animals. Based on these separate sets of data, we will be interested to learn if our environmental conditions can alter the immune system and if so by what mechanism.

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