and memory of contextual fear conditioning in
High Yawning rats.
Gina L. Quirarte
Departamento de Neurobiología Conductual
y Cognitiva, Instituto de Neurobiología,
UNAM Campus Juriquilla, Querétaro,
Neurofisiología de la Conducta y Control
Motor, Instituto de Fisiología,
Benemérita Universidad Autónoma de
Puebla, Puebla, México.
The high frequency of
yawning shown by HY sub-line of rats, derived
from the Sprague-Dawley (SD) strain of rats has
been related to an imbalance of the central
cholinergic system. It has also been reported
that this neurotransmitter system is importantly
involved in learning and memory of
aversively-motivated tasks. Thus, high frequency
of yawning and facilitation of learning and
memory are observed, within certain limits, when
there is an augmented cholinergic tone.
These data led us to
investigate whether the processes of learning
and memory of HY rats differ from those of
normal Sprague-Dawley rats. Contextual fear
conditioning, an aversively-motivated task, was
studied. During the training session each rat
was exposed to a distinct context (CS) which was
paired with a foot-shock (UCS) of either 0, 1.0,
or 2.0 mA, that was presented 8 times, with an
interval of 1 min between foot-shocks. Long-term
memory was measured at 48 and 96 h after
training; during these two test sessions the
foot-shocks were omitted. The conditioned
response was defined as the amount of freezing
across the training and test
Even though HY rats
showed learning and memory of contextual fear
conditioning, their performance was poorer than
that of the SD rats. These impairments seen in
HY rats might be related to altered cholinergic
activity in these rats.
The authors gratefully acknowledge the
technical assistance of Ángel
Méndez, Norma Serafín, Andrea C.
Medina, Martín García and Omar
González. This work was supported by
PAPIIT (Project IN208110).