Activation of G protein-coupled ␣ 2 adrenergic receptors (ARs) inhibits epileptiform activity in the hippocampal CA3 region. The specific mechanism underlying this action is unclear. This study investigated which subtype(s) of ␣ 2 ARs and G proteins (G␣ o or G␣ i ) are involved in this response using recordings of mouse hippocampal CA3 epileptiform bursts. Application of epinephrine (EPI) or norepinephrine (NE) reduced the frequency of bursts in a concentration-dependent manner: (Ϫ)EPI Ͼ (Ϫ)NE ϾϾϾ (ϩ)NE. To identify the ␣ 2 AR subtype involved, equilibrium dissociation constants (pK b ) were determined for the selective ␣AR antagonists atipamezole (8.79), rauwolscine (7.75), 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane hydrochloride (WB-4101; 6.87), and prazosin (5.71). Calculated pK b values correlated best with affinities determined previously for the mouse ␣ 2A AR subtype (r ϭ 0.98, slope ϭ 1.07). Furthermore, the inhibitory effects of EPI were lost in hippocampal slices from ␣ 2A AR-but not ␣ 2C AR-knockout mice. Pretreatment with pertussis toxin also reduced the EPImediated inhibition of epileptiform bursts. Finally, using knock-in mice with point mutations that disrupt regulator of G protein signaling (RGS) binding to G␣ subunits to enhance signaling by that G protein, the EPI-mediated inhibition of bursts was significantly more potent in slices from RGS-insensitive G␣ o G184S heterozygous (G␣ o ϩ/GS) mice compared with either G␣ i2 G184S heterozygous (G␣ i2 ϩ/GS) or control mice (EC 50 ϭ 2.5 versus 19 and 23 nM, respectively). Together, these findings indicate that the inhibitory effect of EPI on hippocampal CA3 epileptiform activity uses an ␣ 2A AR/G␣ o protein-mediated pathway under strong inhibitory control by RGS proteins. This suggests a possible role for RGS inhibitors or selective ␣ 2A AR agonists as a novel antiepileptic drug therapy.

The undergraduate years are a critical time to engage students in research, but opportunities are sparse for rural and tribal students who are an underrepresented demographic in research labs. To reach this population, we have given special consideration to recruitment, lab experience, and retention. This has included partnering with successful Native American scientists and faculty at rural and tribal colleges, campus visits, and addressing the unique needs of this demographic. Utilizing a peer mentoring approach, we have trained 30 rural and tribal students in our lab and through a Research Experience for Undergraduates program. Peer mentoring in a research laboratory creates an environment which encourages students to continue in research. New students are paired with experienced undergraduates and gradually introduced to techniques and concepts. Undergraduates are supported in their strengths within the lab and encouraged to help spread their expertise to other students; advice and encouragement are plentiful from peers and faculty. This makes for a positive lab experience, promoting interest in research and science, and opening new career avenues. This approach has been effective, resulting in a significant number progressing to graduate or medical school, or secondary science education. Supported in part by ND EPSCoR, NSF CAREER 0347259, NSF REU Site 0639227, and the American Physiological Society.

Norepinephrine (NE) has potent antiepileptic properties, the pharmacology of which is unclear. The hippocampal CA3 region is vulnerable to over‐excitation (epileptiform burst activity). When GABAergic inhibition is blocked, NE reduces epileptiform activity through alpha‐2 adrenergic receptor (α2 AR) activation on pyramidal cells. We investigated which α2 AR subtype(s) mediate this effect. α2 AR mRNA expression using RT‐PCR in the CA3 region suggested that α2A AR subtype predominates relative to α2C AR and no α2B AR. Using field potential recordings in hippocampal slices we tested CA3 epileptiform activity. With a beta AR blockade, concentration‐response curves for AR agonists suggest that α2A ARs mediate CA3 epileptiform activity inhibition. Equilibrium dissociation constants (Kb) of selective alpha AR antagonists were determined to confirm the specific α2 AR subtype involved. Kb values correlated best with the α2A, but not the α2B and α2C AR subtypes. The results show that under impaired GABAergic inhibition, activation of α2A ARs is primarily responsible for antiepileptic action of NE. These findings increase our understanding of the role NE plays in attenuating epileptogenesis, and may aid the development of a subtype‐selective α2 AR agonist‐based strategy for treating seizures. Supported by NSF ND EPSCoR, NSF CAREER, NSF REU Site, NSF RET, NIH INBRE, EF, APS Explorations Program for Native Americans.

G‐protein coupled α2 adrenergic receptor (AR) activation by epinephrine (EPI) inhibits epileptiform activity in the mouse hippocampal CA3 region. The mechanism underlying this action is unclear. This study investigated which subtypes of α2ARs, G‐proteins (Gαo or Gαi), and RGS proteins were involved in this response using recordings of hippocampal CA3 epileptiform bursts in mouse brain slices. First, we determined that this effect was mediated by the α2AAR subtype as the inhibitory action of EPI on epileptiform burst frequency was abolished in slices from α2AAR, but not α2CAR, knockout mice. Next, using transgenic mice with the G184S Gnai2 allele (knock‐ins) which interrupts G‐protein α unit binding to regulators of G‐protein signaling (RGS), we found that the α2AAR antiepileptic effects of EPI were enhanced in hippocampal slices from mutant Gαo mice but not Gαi2 mice. Finally, hypomorph mice with very low RGS7 protein levels were found to have increased α2AAR‐mediated hippocampal antiepileptic actions compared to their littermate controls. These results indicate that the EPI‐mediated inhibition of mouse hippocampal CA3 epileptiform burst activity is through an α2AAR/Gαo‐mediated pathway under strong inhibitory control by proteins of the RGS7 family. This suggests a possible role for selective α2AAR agonists or RGS7 inhibitors as a novel antiepileptic drug therapy.

Activation of α2A adrenergic receptors by epinephrine (EPI) attenuates seizure activity in the rat hippocampal CA3 region. Questions concerning the specific mechanism of this action are whether the α2A receptors are located pre‐ or post‐synaptically, and what subtype of G protein is coupled to this receptor. Evidence suggests that pre‐synaptic terminals of the recurrent axon collateral on pyramidal cells are involved; we hypothesize that the α2A receptors are located pre‐synaptically. We used transgenic mice with knock‐ins of the inhibitory regulators of G‐protein signaling (RGS)‐insensitive G183S Gnai2 allele for either the pre‐synaptic Gαo or the post‐synaptic Gαi2 protein subtype. EPI's anti‐epileptic effects were assessed with electrophysiological recordings in brain slices from control mice, modified Gαo mice, and modified Gαi2 mice.The EC50 of EPI was not significantly different between age‐matched C57BL/6J control and modified Gαi2 mice. In contrast, EPI was significantly more potent (>7‐fold) in the Gαo mice than the littermate controls. These results suggest that the pre‐synaptic Gαo protein and not the post‐synaptic Gαi2 protein mediates EPI's inhibition of hippocampal CA3 epileptiform activity. These findings could lead to new strategies for treating epilepsy. Supported by ND EPSCoR, NSF CAREER 0347259, NSF REU Site 0639227, NIH 5RO1GM039561, NIH P20 RR016741 from the INBRE Program, APS.