Pituitary-adrenocortical responsiveness to histaminergic stimulation during social stress of crowding in rats

Stress-Induced Microglia Activation and Monocyte Trafficking to the Brain Underlie the Development of Anxiety and Depression

Psychosocial stress is capable of causing immune dysregulation and increased neuroinflammatory signaling by repeated activation of the neuroendocrine and autonomic systems that may contribute to the development of anxiety and depression. The stress model of repeated social defeat (RSD) recapitulates many of the stress-driven alterations in the neuroimmune system seen in humans experiencing repeated forms of stress and associated affective disorders. For example, RSD-induced neuronal and microglia activation corresponds with sympathetic outflow to the peripheral immune system and increased ability of bone marrow derived myeloid progenitor cells (MPC) to redistribute throughout the body, including to the central nervous system (CNS), reinforcing stress-associated behaviors. An overview of the neuroendocrine, immunological, and behavioral stress-induced responses will be reviewed in this chapter using RSD to illustrate the mechanisms leading to stress-related alterations in inflammation in both the periphery and CNS, and stress-related changes in behavioral responses.

Overcrowding induces anxiety and causes loss of serotonin 5HT-1a receptors in rats

Unfavorable conditions under which children grow up may contribute significantly to the development of psychiatric abnormalities in adult life. We studied the effects of overcrowding at an early age and how it may result in anxiety later in life. Sprague-Dawley rats were housed 10 animals per cage, from birth until 4 weeks post-weaning. Rats housed 3 per cage served as controls. The Elevated Plus maze was used to determine their anxious behavior. Thereafter, the serotonergic system in the hippocampus was investigated. Overcrowded rats were significantly more anxious than controls. The number of 5HT-1a receptors in the hippocampus decreased significantly and their affinity for the ligand, OH-DPAT, increased significantly. There was no significant difference in the hippocampal levels of serotonin between overcrowded rats and controls. Our study shows that overcrowding during childhood can result in anxious behavior and that the serotonergic system appears to play a role in its manifestation.