Strain- and context-based 50 kHz ultrasonic vocalizations and anxiety behaviour in the Wistar-Kyoto rat.

Rodent ultrasonic vocalizations (USVs) are influenced by immediate, prior contexts and have emerged as important indicators that monitor an individual’s ‘state’. They also index direct reflections of inherent ‘trait’ and are suggested to constitute non-invasive read-outs of pathological conditions. Analysis of USVs emitted under particular contexts could help discern strain-specific differences and existence of individual USV profiles. USVs of the Wistar-Kyoto (WKY) strain, a putative model of depression, could indicate social communication deficits. In the cage, USV emission was significantly reduced in WKYs. An elevated plus maze exposure led to no change in USV emission in WKYs, while it significantly reduced USVs in Wistars. Re-exposure induced strain-specific differences in behaviour and total calling time. Sonographic patterns indicated that the predominant USV subtype were flat 50 kHz USVs. EPMexposure induced a reduction in peak amplitude in WKY USVs and in USV length in both strains. USV peak frequency and amplitude, genetically determined spectral features, were strain-specific, while bandwidth and temporal features such as total calling time and USV duration were context-dependent. WKY USVs demonstrated characteristic spectral structures such as increased call length and reduced peak frequency while other parameters were not quantitatively different, reflecting the shared phylogeny between Wistars and WKYs.

Acetylcholinesterase in central vocal control nuclei of the zebra finch (Taeniopygia guttata).

The distribution of acetylcholinesterase (AChE) in the central vocal control nuclei of the zebra finch was studied using enzyme histochemistry. AChE fibres and cells are intensely labelled in the forebrain nucleus area X, strongly labelled in high vocal centre (HVC) perikarya, and moderately to lightly labelled in the somata and neuropil of vocal control nuclei robust nucleus of arcopallium (RA), medial magnocellular nucleus of the anterior nidopallium (MMAN) and lateral magnocellular nucleus of the anterior nidopallium (LMAN). The identified sites of cholinergic and/or cholinoceptive neurons are similar to the cholinergic presence in vocal control regions of other songbirds such as the song sparrow, starling and another genus of the zebra finch (Poephila guttata), and to a certain extent in parallel vocal control regions in vocalizing birds such as the budgerigar. AChE presence in the vocal control system suggests innervation by either afferent projecting cholinergic systems and/or local circuit cholinergic neurons. Co-occurrence with choline acetyltransferase (ChAT) indicates efferent cholinergic projections. The cholinergic presence in parts of the zebra finch vocal control system, such as the area X, that is also intricately wired with parts of the basal ganglia, the descending fibre tracts and brain stem nuclei could underlie this circuitry's involvement in sensory processing and motor control of song