Evaluation of the alpha(2A)-adrenergic receptor gene in a heritable form of temporal lobe epilepsy

5-HT/GABA interaction in epilepsy

Epilepsy is a neurological condition characterized by synchronous neuronal oscillations (seizures) in the electroencephalogram. Seizures are classified in focal or generalized (depending on the brain territory interested during seizures), and in convulsive and/or not convulsive (depending on the presence or not of involuntary movements). The current pharmacological treatments are mainly based on GABA modulation although different neurotransmitters are also involved in epilepsy, including serotonin. However despite much extensive progress in the understanding of epilepsy mechanisms, still, a percentage of people with epilepsy are pharmaco-resistant calling for the need for new therapeutic targets. Here we review preclinical and human evidence showing that serotonin modulates epilepsy that this likely happens via a major modulation/interaction with GABA.

α2 adrenergic receptor dysregulation in depressive disorders: implications for the neurobiology of depression and antidepressant therapy

Dysfunction in noradrenergic neurotransmission has long been theorized to occur in depressive disorders. The α2 adrenergic receptor (AR) family, as a group of key players in regulating the noradrenergic system, has been investigated for involvement in the neurobiology of depression and mechanisms of antidepressant therapies. However, a clear picture of the α2ARs in depressive disorders has not been established due to the existence of apparently conflicting findings in the literature. In this article, we report that a careful accounting of methodological differences within the literature can resolve the present lack of consensus on involvement of α2ARs in depression. In particular, the pharmacological properties of the radioligand (e.g. agonist versus antagonist) utilized for determining receptor density are crucial in determining study outcome. Upregulation of α2AR density detected by radiolabeled agonists but not by antagonists in patients with depressive disorders suggests a selective increase in the density of high-affinity conformational state α2ARs, which is indicative of enhanced G protein coupling to the receptor. Importantly, this high-affinity state α2AR upregulation can be normalized with antidepressant treatments. Thus, depressive disorders appear to be associated with increased α2AR sensitivity and responsiveness, which may represent a physiological basis for the putative noradrenergic dysfunction in depressive disorders. In addition, we review changes in some key α2AR accessory proteins in depressive disorders and discuss their potential contribution to α2AR dysfunction.

Regulation of alpha2AR trafficking and signaling by interacting proteins

The continuing discovery of new G protein-coupled receptor (GPCR) interacting proteins and clarification of the functional consequences of these interactions has revealed multiple roles for these events. Some of these interactions serve to scaffold GPCRs to particular cellular micro-compartments or to tether them to defined signaling molecules, while other GPCR-protein interactions control GPCR trafficking and the kinetics of GPCR-mediated signaling transduction. This review provides a general overview of the variety of GPCR-protein interactions reported to date, and then focuses on one prototypical GPCR, the alpha(2)AR, and the in vitro and in vivo significance of its reciprocal interactions with arrestin and spinophilin. It seems appropriate to recognize the life and career of Arthur Hancock with a summary of studies that both affirm and surprise our preconceived notions of how nature is designed, as his career-long efforts similarly affirmed the complexity of human biology and attempted to surprise pathological changes in that biology with novel, discovery-based therapeutic interventions. Dr. Hancock's love of life, of family, and of commitment to making the world a better place are a model of the life well lived, and truly missed by those who were privileged to know, and thus love, him.

Systemic overexpression of the alpha 1B-adrenergic receptor in mice: an animal model of epilepsy

PURPOSE

A lack of selective alpha1-adrenergic receptor (alpha1-ARs) agonists and antagonists has made it difficult to clarify the precise function of these receptors in the CNS. We recently generated transgenic mice that overexpress either wild-type or a constitutively active mutant alpha 1B-AR in tissues that normally express the receptor. Both wild-type and mutant mice showed an age-progressive neurodegeneration with locomotor impairment and probable stress-induced motor events, which can be partially reversed by alpha 1-AR antagonists. We hypothesized that the wild-type and mutant mice may exhibit spontaneous epileptogenicity as compared with normal (nontransgenic) mice.

METHODS

Normal, wild-type, and mutant mice were studied. Twenty mice (1 year old) underwent prolonged video-EEG monitoring over a 4-week period. Raw EEG data were blindly analyzed by visual inspection for the presence of interictal and ictal epileptic activities.

RESULTS

During the acute postoperative period (< or = 3 days), both wild-type (26.1 +/- 8.07 spikes/day) and mutant mice (116.87 +/- 55.13) exhibited more frequent interictal spikes than did normal mice (2.17 +/- 0.75; p value, <0.05), but all three groups showed EEG and clinical seizures. During the later monitoring periods (>3 days), wild-type and mutant mice showed more frequent interictal spikes (15.44 +/- 4.07; p < 0.01; and 6.05 +/- 2.46; p < 0.05, respectively) as compared with normal mice (0.41 +/- 0.41), but only mutant mice had spontaneous clinical seizures (means +/- SEM).

CONCLUSIONS

The selective overexpression of the alpha 1B-AR is associated with increased in vivo spontaneous interictal epileptogenicity and EEG/behavioral seizures. These results suggest a possible role (direct or indirect) for the alpha 1B-ARs in the development and expression of epileptogenicity.

Genetic polymorphisms of adrenergic receptors

Recent advances in molecular biology have enhanced the understanding of adrenergic receptors. They have allowed the characterization of the several subtypes of adrenergic receptors expressed and have expanded the research about the potential physiologic functions they mediate. Furthermore, variant forms, or polymorphims, of the genes that code for these receptors are being identified. These genetic variants may or may not result in functional differences in the receptors they encode. There is obvious interest in determining the physiologic and clinical relevance of these polymorphisms. The purpose of this review is to describe these polymorphisms and the often contradictory literature pertaining to their clinical significance. Progress in this area is being made at a rapid pace. As the allele-disease relations become less equivocal, it might be possible to predict individual differences in susceptibility to a disease, disease prognosis, and response to treatment.