Early experience, ultrasonic vocalizations, and maternal responsiveness in rats

Abstract

Following a 2-min exposure to 5-6"C, neonatal rats emit ultrasounds for about 5 min, resulting in effective maternal care. Five minutes of 5 6°C causes prolonged ultrasonic vocalizations and correlated agitation in the mothers. The nonlinear effects of variable intensities of neonatal stimulation appear to be related to these differences in maternal behavior.Experimental investigations of the effects of infantile stimulation upon subsequent development of mammals have been reviewed by Levine (1962), Schaefer (1968, Denenberg and Zarrow (1971), andRussell (1971). The considerable body of evidence reviewed by these investigators indicates that such infantile stimulation as handling, electric shock, cold stress, shaking, and similar procedures are potent variables for modifying the developing morphology, physiology, and behavior of mammals. (Most of the research has been conducted using rodents. The relatively few extant studies using more complex species report similar findings.) Most of the developmental changes which have been shown to be modifiable by the above-specified early experiences can be classified as involving one or more of the following classes of dependent variables: growth rate, responsiveness to stressors, resistance to physiological insult (e.g., disease, toxins, starvation), and emotionality. (See Denenberg & Zarrow for a review of specific endpoints.) Regardless of the type of stimulation employed-handling, shock, cold stress, vibration-the effects appear to be similar, both in terms of endpoints affected and in terms of the quantitative characteristics of the endpoints. When the dimension of intensity of early experience has been manipulated it is characteristically the "mild or intermediate" intensity whch produces the greatest effect when compared to unstimulated controls, rather than the extreme intensities (Denenberg, 1964).Whereas the effects of early experience have been relatively well documented, little agreement has evolved about the mediating mechanism(s) underlying the phenomena.

Adoption reverses the long-term impairment in glucocorticoid feedback induced by prenatal stress

“…First, changes in maternal behavior can play a role, as we and others (Misanin et al, 1977) have found that foster mothers provide more maternal attention and stimulation to the pups than do the biological mothers. This mechanism has also been proposed to account for the long-term effects observed after other forms of neonatal stimulation (Bell et al, 1974;Hennessy et al, 1988). Second, changes in the hormonal status of the mother may be involved in the effects of adoption per se.…”

Manipulations During the Second, but not the First, Week of Life Increase Susceptibility to Cocaine Self-Administration in Female Rats

“…In fact, the rodent dam is sensitive to the changing stimulus qualities of the pups (Meier and Schutzman, 1968;Young, 1965) and shows systematic changes in maternal behavior depending on the nature of the treatment that the offspring have received (Barnett and Burn, 1967;Bell et al, 1974) and the time during lactation in which the manipulations occur (Smotherman et al, 1977a, b). It has been demonstrated that heightened maternal behavior results from pup cues elicited by more intense treatments such as electric shock (0.4 mA) (Smotherman et al, 1977a, b).…”

Acquisition and expression of a socially mediated separation response

“…The effects of an infant's formation of early life relationships and its social interactions with caretakers are known to last well in to adulthood with both beneficial and harmful effects [28,35,70]. In our laboratory, we study the development of social relationships between infant rats and their dams, sires, and littermates using an isolation, reunion, and re-isolation test paradigm.Infant rats emit ultrasonic vocalizations (USV) in a variety of situations, including as a response to isolation, physical manipulation, and thermal and olfactory challenge [1][2][3]6,19,25,46,79,80,82,97]. Many researchers have used the presence and absence of these sounds to make inferences about the internal state of the rodents, e.g., isolation-induced USV's have often been called "distress vocalizations" [29,76,78].…”