In adult neurons, GABA acts as the primary inhibitory transmitter. In contrast, in the developing hypothalamus GABA can be excitatory by depolarizing the membrane potential, raising cytosolic calcium, and evoking action potentials. The present proposal focuses on early synapse formation in GABAergic neurons. Converging approaches utilizing fura-2 digital calcium imaging, immunocytochemistry, Northern blot mRNA analysis, and whole cell patch clamp recording with gramididin perforations address five hypotheses. Each set of experiments tests a specific hypothesis regarding GABA's early excitatory role, using both cultured hypothalamic neurons and hypothalamic slices from rats or mice. The first set of experiments addresses the hypothesis that GABA is released from axonal growth cones prior to synapse formation, and that this release is modulated by other transmitters receptors on the growing axon. We test the hypothesis that trophic factors, specifically NT-3 and BDNF, exert rapid physiological effects at the GABA developing synapse in culture and slice. This rapid action will enhance GABA release during the period when GABA is excitatory, but this enhancing effect will disappear in older neurons. The hypothesis that activity-related release of GABA will strengthen developing GABAergic synapses by a long-lasting increase in the evoked response will be tested in cultured neurons; identification of GABAergic neurons will be aided by the use of transgenic mice that express the jellyfish gene for GFP in cultured hypothalamic GABAergic cells. The hypothesis that synaptic release of GABA enhances the expression of genes coding for synaptic proteins and transcription factors in developing, but not mature, synaptic coupled neurons will be tested with Northern blot analysis. The final set of experiments pursues our earlier work showing that GABA reverts from its adult inhibitory action to an excitatory one after neuronal injury in culture. This will be extended to test the hypothesis that injury directly to the brain will result in depolarizing actions of GABA. The hypothalamus controls body temperature, the endocrine system, circadian rhythms, the autonomic nervous system, gender differentiation, energy homeostasis, and water balance, and many of the synapses involved in these functions release GABA. GABA's excitatory actions during development are not restricted to the hypothalamus, but rather are widespread throughout the brain. Thus, what we learn from our experiments on hypothalamic neurons should have general applicability to other CNS neurons.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS034887-06
Application #
6187275
Study Section
Special Emphasis Panel (ZRG1-MDCN-7 (01))
Program Officer
Behar, Toby
Project Start
1995-09-30
Project End
2003-08-31
Budget Start
2000-09-01
Budget End
2001-08-31
Support Year
6
Fiscal Year
2000
Total Cost
$272,666
Indirect Cost
Name
Yale University
Department
Neurosurgery
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
Yao, Yang; Fu, Li-Ying; Zhang, Xiaobing et al. (2012) Vasopressin and oxytocin excite MCH neurons, but not other lateral hypothalamic GABA neurons. Am J Physiol Regul Integr Comp Physiol 302:R815-24
Fu, Li-Ying; van den Pol, Anthony N (2010) Kisspeptin directly excites anorexigenic proopiomelanocortin neurons but inhibits orexigenic neuropeptide Y cells by an indirect synaptic mechanism. J Neurosci 30:10205-19
Acuna-Goycolea, Claudio; Obrietan, Karl; van den Pol, Anthony N (2010) Cannabinoids excite circadian clock neurons. J Neurosci 30:10061-6
van den Pol, Anthony N (2010) Excitatory neuromodulator reduces dopamine release, enhancing prolactin secretion. Neuron 65:147-9
van den Pol, Anthony N (2009) Viral infection leading to brain dysfunction: more prevalent than appreciated? Neuron 64:17-20
van den Pol, Anthony N; Ozduman, Koray; Wollmann, Guido et al. (2009) Viral strategies for studying the brain, including a replication-restricted self-amplifying delta-G vesicular stomatis virus that rapidly expresses transgenes in brain and can generate a multicolor golgi-like expression. J Comp Neurol 516:456-81
van den Pol, Anthony N; Yao, Yang; Fu, Li-Ying et al. (2009) Neuromedin B and gastrin-releasing peptide excite arcuate nucleus neuropeptide Y neurons in a novel transgenic mouse expressing strong Renilla green fluorescent protein in NPY neurons. J Neurosci 29:4622-39
Li, Ying; van den Pol, Anthony N (2009) Enhanced excitatory input to melanin concentrating hormone neurons during developmental period of high food intake is mediated by GABA. J Neurosci 29:15195-204
Acuna-Goycolea, Claudio; van den Pol, Anthony N (2009) Neuroendocrine proopiomelanocortin neurons are excited by hypocretin/orexin. J Neurosci 29:1503-13
Li, Ying; van den Pol, Anthony N (2008) Mu-opioid receptor-mediated depression of the hypothalamic hypocretin/orexin arousal system. J Neurosci 28:2814-9

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