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Distinct α subunit variations of the hypothalamic GABAA receptor triplets (αβγ) are linked to hibernating state in hamsters.

Alò R, Avolio E, Di Vito A, Carelli A, Facciolo RM, Canonaco M - BMC Neurosci (2010)

Bottom Line: At the same time α2 subunit levels proved to be typical of periventricular nucleus (Pe) and Arc of HIB, while strong α4 expression levels were detected during awakening state in the key circadian hypothalamic station, i.e. the suprachiasmatic nucleus (Sch; 60%).We conclude that different αβγ subunits are operating as major elements either at the onset of torpor or during induction of the arousal state in the Syrian golden hamster.The identification of a brain regional distribution pattern of distinct GABAAR subunit combinations may prove to be very useful for highlighting GABAergic mechanisms functioning at least during the different physiological states of hibernators and this may have interesting therapeutic bearings on neurological sleeping disorders.

View Article: PubMed Central - HTML - PubMed

Affiliation: Comparative Neuroanatomy Laboratory, Ecology Department, University of Calabria, Ponte Pietro Bucci, 87030 Arcavacata di Rende, Cosenza, Italy. canonaco@unical.it

ABSTRACT

Background: The structural arrangement of the γ-aminobutyric acid type A receptor (GABAAR) is known to be crucial for the maintenance of cerebral-dependent homeostatic mechanisms during the promotion of highly adaptive neurophysiological events of the permissive hibernating rodent, i.e the Syrian golden hamster. In this study, in vitro quantitative autoradiography and in situ hybridization were assessed in major hypothalamic nuclei. Reverse Transcription Reaction-Polymerase chain reaction (RT-PCR) tests were performed for specific GABAAR receptor subunit gene primers synthases of non-hibernating (NHIB) and hibernating (HIB) hamsters. Attempts were made to identify the type of αβγ subunit combinations operating during the switching ON/OFF of neuronal activities in some hypothalamic nuclei of hibernators.

Results: Both autoradiography and molecular analysis supplied distinct expression patterns of all α subunits considered as shown by a strong (p < 0.01) prevalence of α1 ratio (over total α subunits considered in the present study) in the medial preoptic area (MPOA) and arcuate nucleus (Arc) of NHIBs with respect to HIBs. At the same time α2 subunit levels proved to be typical of periventricular nucleus (Pe) and Arc of HIB, while strong α4 expression levels were detected during awakening state in the key circadian hypothalamic station, i.e. the suprachiasmatic nucleus (Sch; 60%). Regarding the other two subunits (β and γ), elevated β3 and γ3 mRNAs levels mostly characterized MPOA of HIBs, while prevalently elevated expression concentrations of the same subunits were also typical of Sch, even though this time during the awakening state. In the case of Arc, notably elevated levels were obtained for β3 and γ2 during hibernating conditions.

Conclusion: We conclude that different αβγ subunits are operating as major elements either at the onset of torpor or during induction of the arousal state in the Syrian golden hamster. The identification of a brain regional distribution pattern of distinct GABAAR subunit combinations may prove to be very useful for highlighting GABAergic mechanisms functioning at least during the different physiological states of hibernators and this may have interesting therapeutic bearings on neurological sleeping disorders.

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Representative autoradiograms of hypothalamic areas of HIB hamster. Well integral representative transverse sections of hypothalamic areas were used to determine the expression pattern of the α GABAAR subunits considered in the present study. For this purpose oligonucleotidic antisense for α1 (A), α2 (B), α4 (C), and α5 (D) mRNAs developed in the brain of HIB Mesocricetus auratus and was compared to the same subunits (A', B', C', D') for NHIB hamsters with respect to (E) nonspecific binding autoradiograms. In this case the nonspecific binding section of HIB proved to be similar to NHIB and so was used for all determinations. MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.
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Figure 2: Representative autoradiograms of hypothalamic areas of HIB hamster. Well integral representative transverse sections of hypothalamic areas were used to determine the expression pattern of the α GABAAR subunits considered in the present study. For this purpose oligonucleotidic antisense for α1 (A), α2 (B), α4 (C), and α5 (D) mRNAs developed in the brain of HIB Mesocricetus auratus and was compared to the same subunits (A', B', C', D') for NHIB hamsters with respect to (E) nonspecific binding autoradiograms. In this case the nonspecific binding section of HIB proved to be similar to NHIB and so was used for all determinations. MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.

Mentions: Once synthesized, these GABAAR α subunit sequences supplied us with a net heterogeneous distribution pattern of the different α-containing receptors in the above hypothalamic neurons as indicated by low, intermediate and high expression levels in a representative autoradiogram of hypothalamic areas for α1 (Figures 2A, A'), α2 (Figures 2B, B'), α4 (Figures 2C, C') and α5 (Figures 2D, D') subunits with respect to nonspecific binding levels (Figure 2E) of both HIB (A-D) and NHIB (A'-D') hamsters. In the first case, elevated O.D. expression signals (> 0.40 O.D.) of α1 (Figure 3a) were reported to be typical of the medial preoptic area (MPOA) and arcuate nucleus (Arc) in NHIB hamsters while an intermediate level (< 0.4 > 0.18 O.D.) was instead detected for α2 of the periventricular nucleus (Pe) under the same physiological state. As far as HIB hamsters are concerned (Figure 3b), intermediate levels of α1 and α2 were reported for both the suprachiasmatic nucleus (Sch) and Arc, resepctively. Conversely the expression of the other two α subunits were either of an intermediate level as in the case of HIB hamsters or of a very low nature (< 0.180 O.D.) for NHIB animals.


Distinct α subunit variations of the hypothalamic GABAA receptor triplets (αβγ) are linked to hibernating state in hamsters.

Alò R, Avolio E, Di Vito A, Carelli A, Facciolo RM, Canonaco M - BMC Neurosci (2010)

Representative autoradiograms of hypothalamic areas of HIB hamster. Well integral representative transverse sections of hypothalamic areas were used to determine the expression pattern of the α GABAAR subunits considered in the present study. For this purpose oligonucleotidic antisense for α1 (A), α2 (B), α4 (C), and α5 (D) mRNAs developed in the brain of HIB Mesocricetus auratus and was compared to the same subunits (A', B', C', D') for NHIB hamsters with respect to (E) nonspecific binding autoradiograms. In this case the nonspecific binding section of HIB proved to be similar to NHIB and so was used for all determinations. MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2944354&req=5

Figure 2: Representative autoradiograms of hypothalamic areas of HIB hamster. Well integral representative transverse sections of hypothalamic areas were used to determine the expression pattern of the α GABAAR subunits considered in the present study. For this purpose oligonucleotidic antisense for α1 (A), α2 (B), α4 (C), and α5 (D) mRNAs developed in the brain of HIB Mesocricetus auratus and was compared to the same subunits (A', B', C', D') for NHIB hamsters with respect to (E) nonspecific binding autoradiograms. In this case the nonspecific binding section of HIB proved to be similar to NHIB and so was used for all determinations. MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.
Mentions: Once synthesized, these GABAAR α subunit sequences supplied us with a net heterogeneous distribution pattern of the different α-containing receptors in the above hypothalamic neurons as indicated by low, intermediate and high expression levels in a representative autoradiogram of hypothalamic areas for α1 (Figures 2A, A'), α2 (Figures 2B, B'), α4 (Figures 2C, C') and α5 (Figures 2D, D') subunits with respect to nonspecific binding levels (Figure 2E) of both HIB (A-D) and NHIB (A'-D') hamsters. In the first case, elevated O.D. expression signals (> 0.40 O.D.) of α1 (Figure 3a) were reported to be typical of the medial preoptic area (MPOA) and arcuate nucleus (Arc) in NHIB hamsters while an intermediate level (< 0.4 > 0.18 O.D.) was instead detected for α2 of the periventricular nucleus (Pe) under the same physiological state. As far as HIB hamsters are concerned (Figure 3b), intermediate levels of α1 and α2 were reported for both the suprachiasmatic nucleus (Sch) and Arc, resepctively. Conversely the expression of the other two α subunits were either of an intermediate level as in the case of HIB hamsters or of a very low nature (< 0.180 O.D.) for NHIB animals.

Bottom Line: At the same time α2 subunit levels proved to be typical of periventricular nucleus (Pe) and Arc of HIB, while strong α4 expression levels were detected during awakening state in the key circadian hypothalamic station, i.e. the suprachiasmatic nucleus (Sch; 60%).We conclude that different αβγ subunits are operating as major elements either at the onset of torpor or during induction of the arousal state in the Syrian golden hamster.The identification of a brain regional distribution pattern of distinct GABAAR subunit combinations may prove to be very useful for highlighting GABAergic mechanisms functioning at least during the different physiological states of hibernators and this may have interesting therapeutic bearings on neurological sleeping disorders.

View Article: PubMed Central - HTML - PubMed

Affiliation: Comparative Neuroanatomy Laboratory, Ecology Department, University of Calabria, Ponte Pietro Bucci, 87030 Arcavacata di Rende, Cosenza, Italy. canonaco@unical.it

ABSTRACT

Background: The structural arrangement of the γ-aminobutyric acid type A receptor (GABAAR) is known to be crucial for the maintenance of cerebral-dependent homeostatic mechanisms during the promotion of highly adaptive neurophysiological events of the permissive hibernating rodent, i.e the Syrian golden hamster. In this study, in vitro quantitative autoradiography and in situ hybridization were assessed in major hypothalamic nuclei. Reverse Transcription Reaction-Polymerase chain reaction (RT-PCR) tests were performed for specific GABAAR receptor subunit gene primers synthases of non-hibernating (NHIB) and hibernating (HIB) hamsters. Attempts were made to identify the type of αβγ subunit combinations operating during the switching ON/OFF of neuronal activities in some hypothalamic nuclei of hibernators.

Results: Both autoradiography and molecular analysis supplied distinct expression patterns of all α subunits considered as shown by a strong (p < 0.01) prevalence of α1 ratio (over total α subunits considered in the present study) in the medial preoptic area (MPOA) and arcuate nucleus (Arc) of NHIBs with respect to HIBs. At the same time α2 subunit levels proved to be typical of periventricular nucleus (Pe) and Arc of HIB, while strong α4 expression levels were detected during awakening state in the key circadian hypothalamic station, i.e. the suprachiasmatic nucleus (Sch; 60%). Regarding the other two subunits (β and γ), elevated β3 and γ3 mRNAs levels mostly characterized MPOA of HIBs, while prevalently elevated expression concentrations of the same subunits were also typical of Sch, even though this time during the awakening state. In the case of Arc, notably elevated levels were obtained for β3 and γ2 during hibernating conditions.

Conclusion: We conclude that different αβγ subunits are operating as major elements either at the onset of torpor or during induction of the arousal state in the Syrian golden hamster. The identification of a brain regional distribution pattern of distinct GABAAR subunit combinations may prove to be very useful for highlighting GABAergic mechanisms functioning at least during the different physiological states of hibernators and this may have interesting therapeutic bearings on neurological sleeping disorders.

Show MeSH