Vasopressin Inhibits Glutamate Release via Two Distinct Modes in the Brainstem

• DOI: 10.1523/jneurosci.5176-05.2006
• Publication Date: 2006-06-08T15:42:39Z
• Authors: T. W. Bailey; Y.-H. Jin; M. W. Doyle; S. M. Smith; M. C. Andresen
• Keywords: Solitary tract

The hypothalamus coordinates autonomic responses in part through arginine vasopressin (AVP) released medial nucleus tractus solitarius (NTS). However, the mechanisms and sites of AVP action within NTS pathways are uncertain. In brainstem slices, we activated solitary tract (ST) primary afferents to release glutamate tested whether modulated synaptic transmission second-order neurons. neurons were classified as second order by ST characteristics or presence anterograde tracers from peripheral baroreceptor afferents. Stimulus recruitment curves indicated ST-EPSCs on individual evoked stimulation single axons. Variance–mean (<i>V–M</i>) analysis revealed uniformly high probability (<i>p</i> ∼ 0.9) an average 19 (<i>N</i>) a quantal size (<i>q</i>) 34.0 ± 4.7 pA. 26 49 neurons, inhibited afferent transmission. most reduced ST-EPSC amplitudes (<i>n</i> = 20) decreasing <i>p</i> 0.65, whereas <i>q</i>, <i>N</i>, conduction times unaffected. V1a antagonist SR49059 alone decreased <i>V</i> increased <i>M</i>, suggesting tonic actions, blocked exogenous 4). other with identical properties, induced failures time without altering <i>V–M</i> relationship successful 6). Interestingly, frequency-depressed not affected AVP. failed alter holding voltage-dependent potassium currents. Thus, regulates two distinct novel state-dependent mechanisms: one, analog, graded presynaptic inhibition terminal other, binary, extraterminal block conducted excitation.