Corticotropin-Releasing Factor Increases Dihydropyridine- and Neurotoxin-Resistant Calcium Currents in Neurons of the Central Amygdala
Abstract
Corticotropin-releasing factor (CRF) is an important mediator of stress responses in the brain, and CRF receptors and CRF-containing neurons and terminals are located within the central nucleus of the amygdala (CeA). CeA neurons possess multiple types of Ca++ channels, including L, N and Q types and a current resistant to saturating concentrations of dihydropyridine and neurotoxin antagonists. In this study, we used whole-cell patch-clamp techniques to study the effects of CRF on whole-cell Ca++ current (ICa) in acutely dissociated CeA neurons and determine components of the current affected. CRF (1–400 nM) increased the peak of the ICa in ≈50% of the CeA neurons recorded. In the remaining neurons, CRF had little effect. The CRF-induced increase in the ICa was concentration dependent and the estimated EC50 value was 14.9 nM. CRF (50 nM) increased the peak ICa by 25 ± 5% (n = 9). CRF produced an increase in both the transient and the steady state current but did not shift the peak of the current-voltage relationship. CRF did not affect the voltage dependence of activation and inactivation, and the CRF effect on ICas was not significantly different when the neuron was held at −80 or −40 mV. The competitive CRF receptor antagonist (α-helical CRF9–41, 3 μM) blocked the CRF-induced increase in ICa, suggesting that the effect of CRF is receptor mediated. CRF (50 nM) enhanced the ICa(20 ± 3%) in the presence of saturating concentrations of the L-type blocker nimodipine and neurotoxin N- and Q-type blockers ω-conotoxin GVIA and ω-conotoxin MVIIC. We conclude that CRF increased, through a receptor mechanism, dihydropyridine- and neurotoxin-resistant current(s) in CeA neurons.
Footnotes
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Send reprint requests to: Dr. Patricia Shinnick-Gallagher, Department of Pharmacology, University of Texas Medical Branch, Galveston, TX 77555-1031. E-mail: patricia.shinnick-gallagher{at}utmb.edu
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1 This work was supported by National Institute of Neurological Diseases and Stroke Grants NS29265 and NS24643 (P.S.G.).
- Abbreviations:
- CRF
- corticotropin-releasing factor
- CeA
- central nucleus of the amygdala
- NIM
- nimodipine
- DHP
- dihydropyridine
- CRF-ir
- corticotropin-releasing factor immunoreactive
- GABA
- γ-aminobutyric acid
- ACTH
- adrenocorticotropin
- HPA
- hypothalamic-pituitary-adrenal
- TEA
- tetraethylammonium chloride
- HEPES
- 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- BAPTA
- 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid TTX, tetrodotoxin
- 4-AP
- 4-aminopyridine
- Aga IVA
- ω-agatoxin IVA
- HVA
- high voltage activated calcium current
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- Received January 10, 1997.
- Accepted September 12, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
