In general I am interested in the way the brain integrates sensory and hormonal information to modulate feeding, reproduction and activity rhythms. One of my main interests resides in the way peripheral signals known to regulate energy balance like ghrelin and leptin modulate behaviors not only related to homeostatic regulation, but also higher order processes like motivation, emotion, and learning. I am currently working on a project where I have determined how peripheral signals like ghrelin modulate the activity of brain circuits associated with motivated behaviors. Some of the questions that I am asking in my program are: Does peripheral ghrelin reach reward circuits? Does peripheral ghrelin modulate the activity of cells in these circuits? Can ghrelin modulate reward-seeking behaviors? Are effects of ghrelin on reward circuits associated selectively to food, or do they generalize to other rewarding stimuli? Are dysfunctions in these systems associated with abnormal feeding behaviors and obesity? I believe that answers to these questions will ultimately lead to novel treatment avenues for decreasing food cravings and perhaps cravings for drugs of abuse.
I am also interested in the hormonal regulation of circadian behavior. Interestingly receptors for metabolic signals like ghrelin, leptin and estrogen are also found in hypothalamic centers associated with circadian rhythmicity, suggesting that these signals could potentially play a role in the regulation of daily or seasonal patterns of behavior, and endocrine function.
Finally, disruptions in hypothalamic centers underlying circadian rhythms produced by ageing may represent the etiology for a variety of pathological conditions that include obesity, menopause, depression, and sleep disorders. The impact of metabolic hormones, and ageing on the circadian system are also the focus of my current projects. A better understanding of how changes in these hormones during ageing affect cells in the circadian system will lead to treatments that maintain biological and behavioral rhythms functioning optimally for a longer period of time.
Abizaid A, Liu Z.W., Andrews Z.B., Shanabrough M, Borok E., Elsworth J., Roth R.H., Sleeman M., Piccioto M., Tschöp, M. Gao X-B, and Horvath T.H. (2006). Ghrelin modulates the activity and synaptic input organization of midbrain dopamine neurons while promoting appetite. Journal of Clinical Investigations, In Press. Andrews ZB, Rivera A, Elsworth JD, Roth RH, Agnati L, Gago B, Abizaid A, Schwartz M, Fuxe K, Horvath TL. (2006) Uncoupling protein-2 promotes nigrostriatal dopamine neuronal function. European Journal of Neuroscience, 24(1):32-6.
Abizaid, A, and Horvath, TL. (2006) Rimonavant- A new hope for the treatment of obesity?. Nature Clinical Practice Endocrinology and Metabolism, 2, 370-371.
Abizaid, A, and Horvath TL (2005) Unraveling neuronal circuitry regulating energy homeostasis: Plasticity in feeding circuits. Drug Discovery Today, Disease Models, 2(3), 191,196.
Halem, HA, Taylor JE, Dong JZ, Shen Y, Datta R, Abizaid A, Diano S, Horvath T, Culler MD. (2005) A novel GHS-R 1a receptor antagonist that blocks ghrelin-induced growth hormone secretion but increases body weight gain. Neuroendocrinology, 81(5): 339-349.
Abizaid, A., Mezei, G., Thanarajasingam, G., and Horvath, T.L. (2005). Estrogen Enhances Light-Induced Activation of Dorsal Raphe Serotonergic Neurons. European Journal of Neuroscience, 21:1536–1546.
Abizaid, A., Horvath, B., Keefe, D. L., Leranth, C.,and Horvath, T.L. (2004). Direct Visual and Circadian Pathways Target Neuroendocrine Cells in Primates. European Journal of Neuroscience, 20; 2767-2776.
Abizaid, A., Mezei, G., Sotonyi, P., Horvath, T.L. (2004). Sex difference in suprachiasmatic nucleus (SCN) neurons emerging late prenataly. European Journal of Neuroscience, 19; 2488-2496.
Abizaid, A., Mezei, G., and Horvath, T.L.(2004). Estradiol enhances light-induced expression of transcription factors in the SCN. Brain Research, 1010, 35-44.
Halem H.A., Taylor J.E., Dong J.Z., Shen Y., Datta R., Abizaid A., Diano S., Horvath T., Zizzari P., Bluet-Pajot M.T., Epelbaum J., Culler M.D. (2004). Novel analogs of ghrelin: physiological and clinical implications. European Journal of Endocrinology; 151 Suppl 2:S071-5
Abizaid, A., Service, G. and Woodside, B. (2004). Effects of estradiol on immediate early gene expression associated with ovulation lactating rats: Role of nutritional status. Brain Research, 1001 (1-2); 72-77.