Frequency-dependent recruitment of fast XXXX and slow neuropeptide neurotransmitter release controls gonadotropin-releasing hormone neuron excitability.

@entity2227 @entity1246 @entity19 @entity535 @entity1176 @entity32898 @entity32897
The anteroventral periventricular nucleus (AVPV) is thought to play a key role in regulating the excitability of @entity1176 (GnRH) neurons that control fertility. Using an angled, parahorizontal brain slice preparation we have undertaken a series of electrophysiological experiments to examine how the AVPV controls GnRH neurons in adult male and female @entity19 . More than half (59%) of GnRH neurons located in the rostral preoptic area were found to receive monosynaptic inputs from the AVPV in a sex-dependent manner. AVPV stimulation frequencies <1 Hz generated short-latency action potentials in GnRH neurons with @entity1246 and @entity2227 mediating >90% of the evoked fast synaptic currents. The AVPV @entity1246 input was dominant and found to excite or inhibit GnRH neurons in a cell-dependent manner. Increasing the AVPV stimulation frequency to 5-10 Hz resulted in the appearance of additional poststimulus inhibitory as well as delayed excitatory responses in GnRH neurons that were independent of ionotropic @entity535 receptors. The inhibition observed immediately following the end of the stimulation period was mediated partly by @entity1246 (B) receptors, while the delayed activation was mediated by the neuropeptide @entity32898 . The latter response was essentially absent in @entity32897 knock-out @entity19 and abolished by a @entity32897 antagonist. Together, these studies show that AVPV neurons provide direct @entity535 and neuropeptidergic inputs to GnRH neurons. Low-frequency activation generates predominant @entity1246 / @entity2227 release with higher frequency activation recruiting release of @entity32898 . This frequency-dependent release of @entity535 and neuropeptide neurotransmitters greatly expands the range of AVPV control of GnRH neuron excitability.
