Differences in spike train variability in rat vasopressin and oxytocin neurons and their relationship to synaptic activity

Chunyan Li, Pradeep K. Tripathi, William Armstrong

Research output: Contribution to journalArticle

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Abstract

The firing pattern of magnocellular neurosecretory neurons is intimately related to hormone release, but the relative contribution of synaptic versus intrinsic factors to the temporal dispersion of spikes is unknown. In the present study, we examined the firing patterns of vasopressin (VP) and oxytocin (OT) supraoptic neurons in coronal slices from virgin female rats, with and without blockade of inhibitory and excitatory synaptic currents. Inhibitory postsynaptic currents (IPSCs) were twice as prevalent as their excitatory counterparts (EPSCs), and both were more prevalent in OT compared with VP neurons. Oxytocin neurons fired more slowly and irregularly than VP neurons near threshold. Blockade of Cl- currents (including tonic and synaptic currents) with picrotoxin reduced interspike interval (ISI) variability of continuously firing OT and VP neurons without altering input resistance or firing rate. Blockade of EPSCs did not affect firing pattern. Phasic bursting neurons (putative VP neurons) were inconsistently affected by broad synaptic blockade, suggesting that intrinsic factors may dominate the ISI distribution during this mode in the slice. Specific blockade of synaptic IPSCs with gabazine also reduced ISI variability, but only in OT neurons. In all cases, the effect of inhibitory blockade on firing pattern was independent of any consistent change in input resistance or firing rate. Since the great majority of IPSCs are randomly distributed, miniature events (mIPSCs) in the coronal slice, these findings imply that even mIPSCs can impart irregularity to the firing pattern of OT neurons in particular, and could be important in regulating spike patterning in vivo. For example, the increased firing variability that precedes bursting in OT neurons during lactation could be related to significant changes in synaptic activity.

Original languageEnglish (US)
Pages (from-to)221-240
Number of pages20
JournalJournal of Physiology
Volume581
Issue number1
DOIs
StatePublished - May 15 2007

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Oxytocin
Vasopressins
Neurons
Inhibitory Postsynaptic Potentials
Intrinsic Factor
Picrotoxin
Lactation
Hormones

All Science Journal Classification (ASJC) codes

  • Physiology

Cite this

Differences in spike train variability in rat vasopressin and oxytocin neurons and their relationship to synaptic activity. / Li, Chunyan; Tripathi, Pradeep K.; Armstrong, William.

In: Journal of Physiology, Vol. 581, No. 1, 15.05.2007, p. 221-240.

Research output: Contribution to journalArticle

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