Cellular Mechanisms Regulating Activity-Dependent Release of Native Brain-Derived Neurotrophic Factor from Hippocampal Neurons

Abstract

Brain-derived neurotrophic factor (BDNF) plays a critical role in activity-dependent modifications of neuronal connectivity and synaptic strength, including establishment of hippocampal long-term potentiation (LTP). To shed light on mechanisms underlying BDNF-dependent synaptic plasticity, the present study was undertaken to characterize release of native BDNF from newborn rat hippocampal neurons in response to physiologically relevant patterns of electrical field stimulation in culture, including tonic stimulation at 5 Hz, bursting stimulation at 25 and 100 Hz, and theta-burst stimulation (TBS). Release was measured using the ELISA in situ technique, developed in our laboratory to quantify secretion of native BDNF without the need to first overexpress the protein to nonphysiological levels. Each stimulation protocol resulted in a significant increase in BDNF release that was tetrodotoxin sensitive and occurred in the absence of glutamate receptor activation. However, 100 Hz tetanus and TBS, stimulus patterns that are most effective in inducing hippocampal LTP, were significantly more effective in releasing native BDNF than lower-frequency stimulation. For all stimulation protocols tested, removal of extracellular calcium, or blockade of N-type calcium channels, prevented BDNF release. Similarly, depletion of intracellular calcium stores with thapsigargin and treatment with dantrolene, an inhibitor of calcium release from caffeine-ryanodine-sensitive stores, markedly inhibited activity-dependent BDNF release. Our results indicate that BDNF release can encode temporal features of hippocampal neuronal activity. The dual requirement for calcium influx through N-type calcium channels and calcium mobilization from intracellular stores strongly implicates a role for calcium-induced calcium release in activity-dependent BDNF secretion.

Single-Cell Characterization of Retrograde Signaling by Brain-Derived Neurotrophic Factor

“…This secretion could be blocked by AMPA and NMDA antagonists and was shown to require an extracellular calcium influx (Hartmann et al, 2001). In other work, it was suggested that BDNF release was prevented by manipulations that interfered with release of calcium from intracellular stores (Balkowiec and Katz, 2002). How some studies differ from ours, however, is that they find that steady-state depolarization cannot elicit BDNF secretion (Kohara et al, 2001;Kojima et al, 2001;Gartner and Staiger, 2002), a result suggested to occur because the intracellular calcium levels required for BDNF secretion can only be obtained through repeated action potential firing.…”

Coordinate action of pre- and postsynaptic brain-derived neurotrophic factor is required for AMPAR trafficking and acquisition of in vitro classical conditioning

“…Studies have also suggested that BDNF itself could induce (Messaoudi et al, 1998) or facilitate (Kovalchuk et al, 2002) LTP expression in the hippocampus. Additional findings that high-frequency stimulation or more natural theta patterns of afferent activity upregulates BDNF expression further corroborate its role in synaptic plasticity (Gooney and Lynch, 2001;Balkowiec and Katz, 2002). Mechanisms underlying the function of BDNF in plasticity include presynaptic (Gottschalk et al, 1998;Pozzo-Miller et al, 1999;Jovanovic et al, 2000;Xu et al, 2000;Zakharenko et al, 2003;Tyler et al, 2006) or postsynaptic actions Lin et al, 1998;Di Luca et al, 2001;Kovalchuk et al, 2002) as well as coordinate pre-and postsynaptic processes (Alder et al, 2005;Gartner et al, 2006).…”

Molecular Identity and Functional Properties of a Novel T-Type Ca2+ Channel Cloned From the Sensory Epithelia of the Mouse Inner Ear

“…Patterned electrical activity and the ensuing changes in Ca 2ϩ transients, opposed to steady firing activity, preferentially stimulate the transcription and secretion of neurotrophins (Balkowiec and Katz 2002). Moreover, electrical activity tightly regulates the expression of neurotrophin receptors, giving insight into a mechanism by which neurotrophins may selectively affect electrically active neurons.…”