Olfactory Bulbs Influence Testosterone Feedback on Gonadotropin Secretion in Male Hamsters on Long or Short Photoperiod

Pieper, David R.; Unthank, P. D.; Shuttie, Denise A.; Lobocki, Catherine; Swann, Jennifer M.; Newman, Sara; Subramanian, Marappa G.

doi:10.1159/000124839

Cited by 22 publications

(19 citation statements)

References 25 publications

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“…Furthermore, the 'direct' photoperiodic drive to the hy pothalamus [4] as evidenced by the increase in pulse fre quency in ovariectomized ewes held under SD was unal tered by Bulbx. These results are in direct contrast to those in the hamster, another highly photoperiodic species, in which increases in basal gonadotropins and a loss of steroid negative feedback is observed in the male following Bulbx [18][19]24], Since the majority of Bulbx studies in hamsters have used males or gonad-intact fe males, a direct comparison with the current study is not possible. Nevertheless, alterations in photoperiod re sponses, whether in the presence or absence of estradiol, were not observed.…”

Section: Discussioncontrasting

confidence: 80%

“…For example, ol factory bulb removal (Bulbx) of hamsters renders them unresponsive to the inhibitory influences of short days [18,19], Basal gonadotropin levels in male hamsters are elevated and they become insensitive to the negative feed back of testosterone [24], In contrast, two nonphotoperiodic species, the male laboratory rat [21] and female pig [23], express a previously silent photoperiodism follow ing olfactory bulb removal. Specifically, rats become sen sitive to the inhibitory effects of short days, and pigs ex hibit anestrous periods during summer and autumn.…”

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confidence: 99%

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Olfactory Bulb Removal Does Not Prevent Gonadotropin or Prolactin Responses to Changing Photoperiod in the Ewe

Jansen

Jackson²

1993

Neuroendocrinology

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The purpose of this study was to determine if bilateral olfactory bulb removal (Bulbx) alters photoperiod-induced changes of gonadotropin and prolactin secretion in the ewe. Ovariectomized (group 1; n = 12) or ovariectomized estradiol-treated (group 2; n = 12) Suffolk ewes underwent Bulbx (7 per group) or sham operations (5 per group). All ewes subsequently were placed into photochambers and exposed to a photoregimen of alternating 16 h light/8 h dark and 10 h light/14 h dark photoperiods. Plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were determined in blood samples taken twice weekly from group 2 ewes. At the end of each 90-day photoregimen blood samples from all ewes in both groups were taken at frequent intervals for 4 h to determine LH pulse parameters. During the initial 16 h light/8 h dark photoperiod, plasma melatonin concentrations were determined for group 2 ewes during a 24-hour period. The completeness of Bulbx was determined at time of necropsy for all Bulbx ewes. In addition, the functional completeness of Bulbx was determined in group 2 ewes by exposing them to ram’s wool and measuring changes in LH secretion. Bulbx did not affect either basal or photoperiod-induced changes in LH, FSH and prolactin in group 2 ewes. LH pulse parameters varied with photoperiod but were not significantly (p > 0.05) affected by Bulbx in either group 1 or group 2 ewes. The normal nocturnal elevation in plasma melatonin concentrations was unaffected by Bulbx. Bulbx prevented the rapid elevation of LH in 6 of 7 ewes following exposure to ram’s wool (p < 0.01 vs. sham). Olfactory bulb removal was greater than 90% complete in all ewes. These results indicate that Bulbx of ewes does not detectably alter the secretion of melatonin, LH, FSH or prolactin, an effect markedly different than that reported for the hamster. We conclude that the olfactory bulbs of the ewe do not tonically influence gonadotropin or prolactin secretion nor do they affect photoresponsiveness.

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Section: Discussioncontrasting

confidence: 80%

mentioning

confidence: 99%

Olfactory Bulb Removal Does Not Prevent Gonadotropin or Prolactin Responses to Changing Photoperiod in the Ewe

Jansen

Jackson²

1993

Neuroendocrinology

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“…The olfactory bulb functions in odour and pheromone perception and is also involved in neuro-hormonal programming of the hypothalamo-pituitary axis [24, 25]. PLCη enzymes may therefore play a role in neural signalling pertaining to memory and learning or neuro-hormonal regulation.…”

Section: Expression Of Plcη Enzymes In Neural and Neuroendocrine Cellsmentioning

confidence: 99%

Phospholipase C-eta Enzymes as Putative Protein Kinase C and Ca<sup>2+</sup> Signalling Components in Neuronal and Neuroendocrine Tissues

et al. 2007

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Phosphoinositol-specific phospholipase C enzymes (PLCs) are central to inositol lipid signalling pathways, facilitating intracellular Ca²⁺ release and protein kinase C activation. A sixth class of phosphoinositol-specific PLC with a novel domain structure, PLC-eta (PLCη) has recently been discovered in mammals. Recent research, reviewed here, shows that this class consists of two enzymes, PLCη1 and PLCη2. Both enzymes hydrolyze phosphatidylinositol 4,5-bisphosphate and are more sensitive to Ca²⁺ than other PLC isozymes and are likely to mediate G-protein-coupled receptor (GPCR) signalling pathways. Both enzymes are expressed in neuron-enriched regions, being abundant in the brain. We demonstrate that they are also expressed in neuroendocrine cell lines. PLCη enzymes therefore represent novel proteins influencing intracellular Ca²⁺ dynamics and protein kinase C activation in the brain and neuroendocrine systems as putative mediation of GPCR regulation.

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“…Scale bar = 50 pm. tion in relation to the photoperiodic control of seasonal reproduction (Pieper et al, 1987;Bittman et al, 1989). For example, olfactory bulbectomy disrupts reproductive responses to light cycles by preventing gonadal regression, which normally occurs under the influence of short photoperiods in hamsters (Pieper et al, 1984(Pieper et al, , 1989.…”

Section: Retinal Projectionsmentioning

confidence: 99%

Visual system of the fossorial mole‐lemmings, Ellobius talpinus and Ellobius lutescens

Herbin¹,

Repérant

Cooper³

1994

J of Comparative Neurology

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Ocular regression in subterranean species has been shown to be associated with a number of alterations in the retina and in retinal pathways. In order to examine the consequences of eye reduction, the visual system was studied in two species of the murine genus, Ellobius, a specialized fossorial rodent. The axial length of the eye is only 2.2 mm in E. lutescens and 2.9 mm in E. talpinus. The mean soma size of ganglion cells in Nissl-stained flatmounts is approximately 10 microns in E. lutescens and 12 microns in E. talpinus. The soma size distribution in both species appears unimodal and falls within a range of 6-17 microns in diameter. The topographic distribution of ganglion cells shows a weak centroperipheral gradient, and an area centralis cannot be distinguished. The total number of neurons in the ganglion cell layer in Nissl-stained flat mounts is 12,000 in E. lutescens and 28,500 in E. talpinus and, following injection of retrograde tracers in the superior colliculus, is, respectively, 3,600 and 20,000. Based on the axial length and maximum ganglion cell density, the calculated retinal magnification factor (20-26 microns/degree) and spatial resolution (0.4-0.9 cycles/degree) of these minute eyes are extremely reduced. Retinofugal projections, demonstrated by autoradiography and horseradish peroxidase histochemistry, are similar to those in other rodents. The superior colliculus is well developed and receives a predominantly contralateral projection. Ganglion cells projecting to the contralateral colliculus are distributed over the entire retina, while cells that project ipsilaterally are restricted to the ventrotemporal region. The dorsal lateral geniculate nucleus has clearly defined binocular and monocular segments, including a partial segregation of regions receiving ipsilateral or contralateral retinal innervation. In addition, a localized region of label is observed medial to the geniculate nucleus. The retina also sends a bilateral projection to the suprachiasmatic nucleus; the intergeniculate leaflet; the pretectum; and the medial, lateral, and dorsal terminal nuclei of the accessory optic system. Sparse retinal projections were also seen in the bed nucleus of the stria terminalis, the anterior thalamus, and the inferior colliculus. A substantial retinal projection is observed in the basal telencephalon, including the cortical amygdaloid region, the diagonal band of Broca, the olfactory tubercle, and the piriform cortex. The results suggest that the morphological constraints of reduced eye size are reflected in the retina by a generally homogeneous organization but that central visual projections are not substantially modified as in some more specialized, strictly subterranean rodents.

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Olfactory Bulbs Influence Testosterone Feedback on Gonadotropin Secretion in Male Hamsters on Long or Short Photoperiod

Cited by 22 publications

References 25 publications

Olfactory Bulb Removal Does Not Prevent Gonadotropin or Prolactin Responses to Changing Photoperiod in the Ewe

Olfactory Bulb Removal Does Not Prevent Gonadotropin or Prolactin Responses to Changing Photoperiod in the Ewe

Phospholipase C-eta Enzymes as Putative Protein Kinase C and Ca<sup>2+</sup> Signalling Components in Neuronal and Neuroendocrine Tissues

Visual system of the fossorial mole‐lemmings, Ellobius talpinus and Ellobius lutescens

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