Stimuli from Conspecifics Influence Brain Mast Cell Population in Male Rats

Abstract

It is well established that mast cells occur within the brain of many species, and that the brain mast cell population is not static, but changes with the behavioral and physiological state of the animal.In this study, we tested whether exposure to conspecifics alters the number of brain mast cells in male rats, and then investigated the nature of stimuli influencing the changes observed in the number and localization of brain mast cells. Five days of cohabitation with an ovariectomized, estrogen-progesterone (OVX + EP)-treated female resulted in the largest number of thalamic mast cells, while pairing with such a female physically separated by a wire mesh or with a novel male produced a smaller, but significant increase over other pairings (OVX females for 5 days, OVX and OVX + EP females for 1 day, familiar or isolated males for 5 days). In all groups, mast cells were localized within specific dorsal thalamic nuclei, including the paraventricular nucleus, anterior nuclear group, or mediodorsal, ventroposterior, or medial geniculate nuclei. The results suggest that the behavioral and/or endocrine factors associated with cohabitation with conspecifics are sufficient to alter the number of brain mast cell-specific nuclei in the thalami of male rats and thus can provide targeted delivery of neuromodulators to specific regions of the brain that process information concerning the normal physiological state of the animal. Keywordsfemale; thalamus; mating; aggressive; endocrine; immune; stress Although mast cells are well known in their role as effectors of IgE-mediated allergic reactions, their physiological function(s) remains poorly understood (Wedemeyer, Tsai, and Galli, 2000; Forsberg, Pejler, Ringwall, Lunderius, Tomasini-Johansson, Kusche-Gullberg, Eriksson, Ledin, Hellman, and Kjellen, 1999;Echtenacher, Mannel, and Hultner, 1996;Malaviya, Ikeda, Ross, and Abraham, 1996). Recent evidence indicates that bacterial recognition followed by endocytosis, processing and presentation of bacterial antigen, immune cell recruitment, and elimination of parasites number among these functions (McLachlan and Abraham, 2001;Vincent-Schneider, Thery, Mazzeo, Tenza, Raposo, and Bonnerot, 2001;Abraham and Malaviya, 2000; Fox, Jewel, and Whitacre, 1994). In addition, mast cells synthesize, store, and secrete a wide variety of bioactive molecules, including neuropeptides, neurotransmitters, prostaglandins, chemotactic factors, and (Galli, 2000;Metcalfe, Baram, and Mekori, 1997;Silver, Silverman, Vitkovic, and Lederhendler, 1996;Johnson and Krenger, 1992).Mast cells are normally present in the mammalian brain, both in the leptomeninges and within the parenchyma along the blood vessels of several dorsal thalamic nuclei (Dropp, 1972(Dropp, , 1976Theoharides, 1990;Goldschmidt, Hough, Glick, and Padawer, 1984). The number of brain mast cells is modulated by physiological and behavioral state. Our demonstration that mature mast cells can migrate from the vasculature into the adult rat brain parenchyma provides a possible mechani...

Effect of Systemic Estradiol Administration on Circadian Body Temperature and Activity Rhythms in Female Rats

“…The decreased body weight by E 2 coincided with that observed in previous studies [41][42][43]. E 2 administration did not affect the food intake per body weight.…”

Brain mast cells link the immune system to anxiety-like behavior

“…Psychological stressors induced through social defeat and isolation stress increased the number of mast cells in the brain (26,63). Last, gonadal hormones from conspecifics during mating also increase mast cell number and activation in the brain (23,62,64).…”

“…However, the function of mast cells in the brain is unknown. A role in normal physiology and behavior is suggested as the brain population of mast cells fluctuates with endocrine status and changes after stress and handling (23)(24)(25)(26). Not surprisingly, there are individual differences in the number of brain mast cells within species (27), perhaps associated with behavioral and/or experiential differences.…”

Brain mast cells are influenced by chemosensory cues associated with estrus induction in female prairie voles (Microtus ochrogaster)

“…3 and 4). Because a previous study had shown that increases in brain mast cells following cohabitation in rats are specific to a particular rostrocaudal extent of the thalamus (Asarian et al, 2002), the distribution of thalamic mast cells was investigated. Mast cells were distributed uniformly throughout the rostrocaudal extent of the thalamus across groups, with most cells being observed in the paraventricular thalamic region directly below the medial habenula.…”

“…In male mice, mast cells increase in discrete thalamic nuclei following mating and cohabitation with a female conspecific (Yang et al, 1999). As in male mice, mast cells increase in sensory, motor, and limbic thalamic regions in male rats following prolonged pairing with an estrogen-progesterone-primed female (Price, 1995;Asarian et al, 2002). Additionally, male Syrian hamsters housed in long day lengths or exposed to conspecific vaginal secretions display elevated brain mast cell numbers (Novak et al, 1994;Novak and Nunez, 1995).…”