title: Axonal projections and conduction properties of olfactory peduncle neurons in the armadillo (Chaetophractus vellerosus).
abstract: Extracellular unit recording was employed to study the axonal properties and efferent projections of antidromically identified neurons in the olfactory peduncle (OP) region of a primitive eutherian macrosmatic mammal, the south american armadillo (Chaetophractus vellerosus). Of 72 cells which satisfied the criteria for antidromic invasion, 55 (76%) and 17 (24%) responded to ipsi- and contralateral olfactory bulb (IOB; COB) stimulation, respectively. The absolute refractory period (3.25 +/- 0.3 ms; mean +/- SE) and the conduction velocity (CV; 1.94 +/- 0.2 m/s; mean +/- SE) of IOB and COB driven neurons were negatively correlated (r = -0.52; p less than 0.001). In paired-shock tests (8-1950 ms interval), and early supernormal period (SPN) of increased CV and excitability was found following the relative refractory period in 82% of tested cells (N = 50); this period was followed by a late subnormal phase (SBN) of decreased CV and increased threshold in 58% of neurons (N = 50). Significant correlations were found to exist between: CV and absolute magnitude of latency variation (r = -0.55; p less than 0.001; n = 43), CV and duration of SPN and SBN periods (r = -0.60; p less than 0.002; n = 24 and r = 0.58; p less than 0.02; n = 19, respectively) and between duration of SPN and SBN phases (r = 0.79; p less than 0.001; n = 30). Maximum latency variation during the SPN and SBN periods was attained in a gradual, additive manner.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001135:Armadillos / Q000502:physiology*; D002490:Central Nervous System / Q000502:physiology*; D005071:Evoked Potentials; D005260:Female; D008297:Male; D009431:Neural Conduction; D009833:Olfactory Pathways / Q000033:anatomy & histology / Q000502:physiology*; D051381:Rats; D011930:Reaction Time / Q000502:physiology; D012032:Refractory Period, Electrophysiological; D013045:Species Specificity; D004490:Xenarthra / Q000502:physiology*