Molecular and behavioral characterization of adolescent protein kinase C following high dose ethanol exposure

Abstract

Rationale Ethanol is commonly used and abused during adolescence. Although adolescents display differential behavioral responses to ethanol, the mechanisms by which this occurs are not known. The PKC pathway has been implicated in mediating many ethanol-related effects in adults, as well as GABAA receptor regulation. Objectives The present study was designed to characterize cortical PKC isoform and GABAA receptor subunit expression during adolescence relative to adults as well as assess PKC involvement in ethanol action. Results Novel PKC isoforms were elevated, while PKCγ was lower during mid-adolescence relative to adults. Whole cell lysate and synaptosomal preparations correlated for all isoforms except PKC δ In parallel, synaptosomal GABAA receptor subunit expression was also developmentally regulated, with GABAAR δ and α4 being lower while α1 and γ2 were higher or similar, respectively, in adolescents compared to adults. Following acute ethanol exposure, synaptosomal novel and atypical PKC isoform expression was decreased only in adolescents. Behaviorally, inhibiting PKC with calphostin C, significantly increased ethanol-induced loss of righting reflex (LORR) in adolescents but not adults, whereas activating PKC with phorbol-dibutyrate was ineffective in adolescents but decreased LORR duration in adults. Further investigation revealed that inhibiting the cytosolic phospholipase A2/arachidonic acid (cPLA2/AA) pathway increased LORR duration in adolescents, but was ineffective in adults. Conclusions These data indicate that PKC isoforms are variably regulated during adolescence and may contribute to adolescent ethanol-related behavior. Furthermore, age-related differences in the cPLA2/AA pathway may contribute to age-related ethanol’s effects on novel and atypical PKC isoform expression and behavior.

Adolescent and adult rat cortical protein kinase A display divergent responses to acute ethanol exposure

“…More than likely, variations in other molecular pathways, such as other protein kinases, may contribute to the remaining gap in ethanol age-dependent hypnotic sensitivity. In support of this, our recent work indicating that cortical PKC activity also contributes to adolescent hypnotic responses further implicates the kinome in developmental ethanol-related behavior (Santerre, Gigante, Landin, & Werner, 2013). …”

“…Although similar waking BECs between adolescents and adults have been noted (Silveri & Spear, 2002), other studies have reported age-related differences in BECs at waking (Broadwater, Varlinskaya, & Spear, 2011; Santerre et al, 2013; Silveri & Spear, 1998). The reasons behind this discrepancy are not clear, but work assessing ontogenetic ethanol metabolic rates in detail indicate that non-metabolic factors likely play a prominent role (Silveri & Spear, 2000).…”

Involvement of the GABAA Receptor in Age‐Dependent Differences in Binge‐Like Ethanol Intake

“…This was shown by a decrease in their level of EtOH intake and BECs with a dose that did not significantly alter the consumption in adults, as well as by the longer duration of the effects induced by 16 mg/kg of THIP. These results could seem surprising, as lower levels of d-subunit have been reported in the adolescent brain (Laurie et al, 1992;Santerre et al, 2014). However, one might suggest that these receptors, despite their lower density, would be more sensitive to EtOH during adolescence, and thus would contribute more importantly to the modulation of alcohol drinking.…”

“…In addition, each subunit exhibits a different developmental trajectory, suggesting that expression and function of GABA A receptors could modify over development (Henschel et al, 2008;Laurie et al, 1992). Interestingly, whereas the expression of c2 remains relatively constant, levels of d-subunit mRNA and protein increase over adolescence, with the highest levels found in adults (Laurie et al, 1992;Santerre et al, 2014). Due to the proposed involvement of d-containing GABA A receptors in the behavioral effects of EtOH, these modifications could contribute to age differences in alcohol consumption.…”

GABAergic contributions to alcohol responsivity during adolescence: Insights from preclinical and clinical studies

“…The most notable developmental changes in GABA A receptor subunits have been reported for α 1 , α 2 , α 5 , β 2 , γ 2 , and δ subunits. In rodent and human studies, expression and regional distribution of the α 1 subunit is low at birth but is up-regulated during the early postnatal period, peaking from P21–28 and then declining by 20% to reach adult levels at P60 (Gambarana, Beattie, Rodriguez, & Siegel, 1991; Santerre, Gigante, Landin, & Werner, 2013). In contrast, the α 2 subunit is more widely distributed at birth and is either constant or declines until adulthood (Laurie, Wisden, & Seeburg, 1992), although α 2 subunits are replaced by α 1 subunits (Fritschy, Paysan, Enna, & Mohler, 1994).…”