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Abstract
We determined CA1 hippocampal field to be involved in self-exposure, a type of novelty‑seeking behaviour that has also been associated with short 22 kHz and flat 50 kHz ultrasonic vocalizations (USV) in adult male Long-Evans rats. Rats were habituated for three days to a self-exposure cage with two nose-poke holes. On day four, the animals from the experimental group were allowed to turn the cage light off for 5 s with a nose‑poke (test/self‑exposure session), while rats from control-yoked group had changing light conditions coupled and identical to the experimental animals. The experimental rats performed more nose-pokes during self-exposure session than animals from the control group. This effect was accompanied by a higher density of c-Fos-positive nuclei in the hippocampal CA1. There were no significant group differences in c-Fos expression in other brain regions analysed. However, possible involvement of several other structures in self-exposure (i.e., CA3, the dentate gyrus, amygdala, prefrontal cortex, and nucleus accumbens) is also discussed, as their correlational activity, reflected by c-Fos immunoactivity, was observed in the experimental rats. During test sessions, there were more nose-pokes accompanied by short 22 kHz calls and 50 kHz calls performed by the rats of the experimental group than of the control group. The CA1 region has previously been associated with novelty; short 22 kHz USV and flat 50 kHz USV could be associated with self-exposure, also they appear to be emitted correlatively.
Highlights
We looked for the parts of the rat brain activated during the self‐exposure, namely: the basolateral (BLA) and cen‐ tral (CeA) amygdalar nuclei, pre‐ (PrL) and infralimbic (IL) cortices, shell (AcbSh) and core (AcbC) of the nucleus accumbens
We examined CA1, CA3, and the dentate gyrus (DG) of the hippocampal formation, as their involve‐ ment in controlling and guiding emotions, motivation, and cognition is well documented (Hess et al, 1995; Moham‐ med et al, 2002; Turner et al, 2002; Knapska et al, 2007)
Ultrasonic vocalizations (USV) emitted by rats are regarded as indicators of their emotional state (Brudzynski 2015)
Summary
Voluntary exploration is a complex type of be‐ haviour that involves emotional, motivational, and cognitive components and is associated with significant and coordinated activation of numerous brain areas (Hess et al, 1995; Mohammed et al, 2002; Turner et al, 2002; Balleine 2005; Knapska et al, 2006; Bourgeois et al, 2012; Kinnavane et al, 2014; Larkin et al, 2014; Comba et al, 2015; Mun et al, 2015). Self‐exposure, CA1‐activation, ultrasonic‐calls 313 the test session, the experimental rats performed more nose‐pokes than the control animals (p
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