Abstract
Yawning is a stereotyped behavioral pattern characterized by wide opening of the mouth associated with deep inspiration followed by short expiration. All vertebrate species yawn, but with low frequencies. We obtained two sublines of Sprague–Dawley (SD) rats by a strict inbreeding process: one with a high-yawning frequency (HY) of 20 yawns/h, which is one order of magnitude higher with respect to the low-yawning frequency (LY) subline, with 2 yawns/h. Outbred SD rats had a yawning frequency of 1 yawn/h. HY dams had a different organization of maternal care with respect to that displayed by LY and SD dams because HY dams constructed lower quality nests and had more re-retrieving and atypical retrieving. The aim of this study was to analyze the changes in maternal care using in- and cross-fostering between the sublines and SD dams and to measure spontaneous and dopaminergic-induced yawning, penile erections, grooming and scratching bouts. We also measured the expression of dopamine D2 receptors in the striatum using Western blot analysis. Our results showed that HY male rats reared by SD or LY dams did not significantly differ in yawning frequencies with respect to HY male rats reared by mothers of their own phenotype. Maternal care did not differ between sublines and SD dams independent of the litter they reared. However, LY rats reared by HY dams showed a significant increase in the number of spontaneous penile erections. Importantly, in-fostered HY male rats had the highest number of yawns induced by systemic administration of (−)-quinpirole supporting that higher maternal care display can influence the frequency of dopaminergic-induced yawning. In fact HY male rats in all conditions yawned more than did LY and SD male rats independent of the dam that raised them supporting a strong influence of genetic background. However SD male rats raised by LY dams showed significantly increased the dopamine D2 receptor expression. In conclusion, maternal care and the environmental nest conditions during the lactation period did not change the phenotypic characteristics of the yawning sublines supporting that their genetic background is fundamental for the expression of spontaneous or dopaminergic-induced yawning.
Highlights
Yawning is a stereotyped behavioral pattern that is characterized by deep inspiration followed by short expiration across all vertebrate species (Barbizet, 1958; Argiolas and Melis, 1998; Collins and Eguibar, 2010)
Basal Spontaneous Yawning Frequency, Penile Erection and Grooming of In-fostered and Cross-fostered Male Rats Raised by Different Dams
Basal Spontaneous Yawning Frequency, Penile Erection, and the Grooming of In-fostered and Cross-fostered Male Rats Raised by Different Dams
Summary
Yawning is a stereotyped behavioral pattern that is characterized by deep inspiration followed by short expiration across all vertebrate species (Barbizet, 1958; Argiolas and Melis, 1998; Collins and Eguibar, 2010). Yawning frequency has a circadian rhythm with a peak before dusk (Anías et al, 1984). The yawning circadian rhythm is not an endogenous mechanism because it is not free running, and it can be synchronized by a restricted feeding period, with food availability being a stronger zeitgeber than a light–dark cycle (Holmgren et al, 1991). These sublines differ in their responses to stress, as seen in the open-field arena, where HY rats are more active than LY rats, indicating that HY rats are less emotionally reactive than the latter (Moyaho et al, 1995)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
