Separation-Induced Receptor Changes in the Hippocampus and Amygdala ofOctodon degus: Influence of Maternal Vocalizations

Abstract

Relatively little is known about the basic mechanisms that play a role in the vulnerability of the developing brain toward adverse environmental influences. Our study in the South American rodent Octodon degus revealed that repeated brief separation from the parents and exposure to an unfamiliar environment induces in the hippocampal formation of male and female pups an upregulation of D1 and 5-HT1A receptor density in the stratum radiatum and stratum lacunosum moleculare of the CA1 region. In the CA3 region, only the 5-HT1A receptors were upregulated; no changes were observed for D1 receptors in this region. GABA(A) receptor density in the hippocampus and amygdala was downregulated (nonsignificant trend) after parental separation. The acoustic presence of the mother during parental separation suppressed the D1 and 5-HT1A receptor upregulation in some regions of the hippocampus; no such suppressing influence was observed for the GABA(A) receptors. In the basomedial amygdala, the maternal calls enhanced the separation-induced 5-HT1A receptor upregulation in the male pups, whereas in the female pups the separation-induced receptor densities were not only suppressed by the maternal call but further downregulated, compared with the control group. These results demonstrate that early adverse emotional experience alters aminergic function within the hippocampus and amygdala and that the mother's voice, a powerful emotional signal, can modulate these effects in the developing limbic system.

Genetic variation in cortico-amygdala serotonin function and risk for stress-related disease

“…The level of 5-HT1A-R binding in basolateral nucleus of the amygdala (BLA) is increased by maternal separation stress in rats (Vicentic et al, 2006) and Octodon degus (Ziabreva et al, 2003). Under non-stressed conditions, application of 5-HT1A-R agonists (e.g., 8-OH-DPAT) inhibits the excitability of neurons in the BLA, while the inhibitory actions of 5-HT on these neurons can be prevented by 5-HT1A-R antagonist coapplication (Cheng et al, 1998;Stein et al, 2000;Wang et al, 1999).…”

THE EFFECTS OF PRE-WEANING SOCIAL ISOLATION AND MOTHER’S PRESENCE ON THE OBJECT EXPLORATION BEHAVIOR OF INFANT <i>OCTODON DEGUS</i>

“…The pups showed a substantial decrease in the number of nicotinamide adenine dinucleotide phosphate-diaphorase-reactive neurons in the dorsal anterior cingulate cortex and in the nucleus accumbens (Poeggel, Lange, Hase, Metzger, Gulyaeva, & Braun, 1999), and an alteration of the balance between serotonergic and dopaminergic innervation of the medial prefrontal cortex (Braun, Lange, Metzger, & Poeggel, 2000). Even short-term social separation from mothers and siblings (from P8 to P10, twice a day, each time for 3 min) resulted in an upregulation of dopaminergic and serotonergic receptor density in the hippocampus (Ziabreva, Poeggel, Schnabel, & Braun, 2003). Braun et al (2003) used neonatal degus and examined the effects of parental separation on exploratory behavior and vocalization in an open field, which was a novel environment for the pups.…”

Juvenile emotional experience alters synaptic composition in the rodent cortex, hippocampus, and lateral amygdala

“…At the synaptic level such chronic deprivation alters synaptic densities and ultrastructure (7,10). Recent studies in rodents after periodic parental separation during the preweaning life span have demonstrated that, analogous to this experience-driven development of sensory and motor systems, the functional maturation of higher associative cortical regions, in particular those that are part of the limbic system, is also strongly influenced by emotional experience (11)(12)(13)(14)(15)(16)(17)(18)(19).…”