Alterations of the cortical representation of the rat ventrum induced by nursing behavior

Abstract

The representation of the surfaces of the trunk was mapped in detail in a series of anesthetized adult female rats to assess cortical representational changes that might be induced in the SI cortical field by a major natural source of a differentially heavy schedule of tactile inputs: the stimulation of the rat ventrum in nursing behavior. Controls included virgin rats and postpartum age-matched rats whose litters were removed on the day of birth. The SI representation of the ventral trunk skin of lactating rats was about 1.6 x larger than in matched postpartum nonlactating or virgin controls. The greatest representational change--about twofold--was for the nipple-bearing skin between the forelimbs and hindlimbs. Indeed, changes in SI representational territory for the middle third of the ventrum, a skin zone without nipples, were not significant. As a rule, the representation of the ventrum skin in lactating rats was at least as topographically ordered as was that reconstructed for nonlactating postpartum and virgin controls. Receptive fields (RFs) representing the ventrum skin in lactating females were about one-third the sizes of those recorded in matched nonlactating or virgin controls. RF size differences were again greater for the representation of the nipple- bearing skin in the anterior and posterior thirds of the ventrum than for the central third. Changes in RF sizes were roughly inversely related to changes in the cortical magnification of representation of the ventrum on the proportion of about 3:2. Interestingly, the glabrous nipple and areolar skin were only weakly represented--or not demonstrably represented--in the SI map of either lactating or control rats. These results indicate that there is a largely unstudied cortical neurology of nursing behavior. Major CNS changes are induced by this dramatic, episodic change in behaviorally important tactile inputs. In turn, input-induced changes presumably contribute to this emergent, rapidly evolving behavior.

Internal body state influences topographical plasticity of sensory representations in the rat gustatory cortex

“…Training involving peripheral stimulation usually modifies the relative representation in primate auditory cortex (5) or in somatosensory cortices of both humans (23), nonhuman primates (24), and rodents (4,25). However, unlike the above cited studies, in our experiments maps rearrangement is caused not by a modification in the stimulus-receptor interaction at the periphery (the bottom-up inputs) but rather by viscero-gustatory interaction that might occur from top-down modulations in early brainstem relays, such as the nucleus of solitary tract (26,27), the parabrachial nucleus (28,29), or CTA-related forebrain centers, such as basolateral amygdala (10) and primary GC (11,12).…”

Comparison of the “Nursing” and Other Parental Behaviors of Nulliparous and Lactating Female Rats

“…This suggests differential sensory regulation of this posture in sensitized and lactating mothers. Under certain conditions, stimulation provided by active pups rooting in their dam's ventrum in search of a nipple produces cellular (Lonstein et al, 1998b;Xerri, Stern, and Merzenich, 1994), endocrine (Jakubowski and Terkel, 1986;Stern and Siegel, 1978), and behavioral consequences in female rats (Stern, 1991). Rooting by pups is not adequate, though, for maximal c-fos transcription within the cPAG or the elicitation of kyphosis in normal lactating dams (Lonstein and Stern, 1997a, b), but is apparently somewhat effective for eliciting kyphosis in sensitized virgins.…”

Nursing-Induced Somatosensory Cortex Plasticity: Temporally Decoupled Changes in Neuronal Receptive Field Properties Are Accompanied by Modifications in Activity-Dependent Protein Expression

“…Cutaneous stimuli induced by nursing gradually abate in a naturalistic context. This episodic behavior has been shown to reshape the SI representation of the ventrum skin of lactating rats (Xerri et al, 1994). It is unknown how the rapidly evolving nursing behavior impacts on the ventrum map in the course and after completion of nursing.…”