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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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β2,3 and γ2,3 levels (O.D. ± s.e.m.) in NHIB and HIB hypothalamic areas. Expression pattern (O.D. ± s.e.m.) of GABAAR β2,3 and γ2,3 mRNAs in a) NHIB and b) HIB hamsters. Statistics: ANOVA and Neuman Keul's test, * p < 0.05; ** p < 0.01; *** p < 0.001. Arc: arcuate hypothalamic nucleus; MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.
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Figure 5: β2,3 and γ2,3 levels (O.D. ± s.e.m.) in NHIB and HIB hypothalamic areas. Expression pattern (O.D. ± s.e.m.) of GABAAR β2,3 and γ2,3 mRNAs in a) NHIB and b) HIB hamsters. Statistics: ANOVA and Neuman Keul's test, * p < 0.05; ** p < 0.01; *** p < 0.001. Arc: arcuate hypothalamic nucleus; MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.

Mentions: A similar trend to that of α subunits was also established for β- and γ-containing neurons in the same hypothalamic areas of NHIB and HIB states. In particular, intermediate levels (< 0.4 > 0.18 O.D) of β2 were reported for Pe and Arc of NHIBs, whereas elevated expression signals (> 0.40 O.D.) were obtained for β3 subunit in Sch and MPOA of the same physiological state (Figure 5a). Curiously in the case of HIBs (Figure 5b), elevated levels of β3 were detected in MPOA, while intermediate levels were typical of Arc and Sch. Regarding γ subunit, it was γ3 that showed very strong densities in Sch and Arc of NHIBs whereas in the case of γ2, only intermediate levels were observed in MPOA and Pe. However, it was still MPOA that maintained notably moderate levels of γ3 in HIBs while this subunit is weakly expressed (< 0.180 O.D.) in Pe and Sch during this same physiological state.


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)

β2,3 and γ2,3 levels (O.D. ± s.e.m.) in NHIB and HIB hypothalamic areas. Expression pattern (O.D. ± s.e.m.) of GABAAR β2,3 and γ2,3 mRNAs in a) NHIB and b) HIB hamsters. Statistics: ANOVA and Neuman Keul's test, * p < 0.05; ** p < 0.01; *** p < 0.001. Arc: arcuate hypothalamic nucleus; 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 5: β2,3 and γ2,3 levels (O.D. ± s.e.m.) in NHIB and HIB hypothalamic areas. Expression pattern (O.D. ± s.e.m.) of GABAAR β2,3 and γ2,3 mRNAs in a) NHIB and b) HIB hamsters. Statistics: ANOVA and Neuman Keul's test, * p < 0.05; ** p < 0.01; *** p < 0.001. Arc: arcuate hypothalamic nucleus; MPOA: medial preoptic area; Pe: periventricolar hypothalamic nucleus; Sch: suprachiasmatic nucleus.
Mentions: A similar trend to that of α subunits was also established for β- and γ-containing neurons in the same hypothalamic areas of NHIB and HIB states. In particular, intermediate levels (< 0.4 > 0.18 O.D) of β2 were reported for Pe and Arc of NHIBs, whereas elevated expression signals (> 0.40 O.D.) were obtained for β3 subunit in Sch and MPOA of the same physiological state (Figure 5a). Curiously in the case of HIBs (Figure 5b), elevated levels of β3 were detected in MPOA, while intermediate levels were typical of Arc and Sch. Regarding γ subunit, it was γ3 that showed very strong densities in Sch and Arc of NHIBs whereas in the case of γ2, only intermediate levels were observed in MPOA and Pe. However, it was still MPOA that maintained notably moderate levels of γ3 in HIBs while this subunit is weakly expressed (< 0.180 O.D.) in Pe and Sch during this same physiological state.

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