Browsing by Author "Hale, Matthew W."

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    Acute Administration of the Nonpathogenic, Saprophytic Bacterium, Mycobacterium vaccae, Induces Activation of Serotonergic Neurons in the Dorsal Raphe Nucleus and Antidepressant-Like Behavior in Association with Mild Hypothermia
    (Springer, 2018) Siebler, Philip H.; Heinze, Jared D.; Kienzle, Drake M.; Hale, Matthew W.; Lukkes, Jodi L.; Donner, Nina C.; Kopelman, Jared M.; Rodriguez, Orlando A.; Lowry, Christopher A.; Psychiatry, School of Medicine
    Peripheral immune activation can have profound physiologic and behavioral effects. One mechanism through which immune activation may affect physiology and behavior is through actions on brainstem neuromodulatory systems, such as serotonergic systems. To test this hypothesis, in Experiment 1, adult male BALB/c mice were implanted with telemetric recording devices and then immunized with Mycobacterium vaccae NCTC 11659 (0.1 mg, s.c.; Days - 28, - 14; N = 36). On Day 1, mice received an acute challenge with M. vaccae (0.1 mg, s.c.) or borate-buffered saline vehicle. Core body temperature and locomotor activity recordings were conducted during a 36 h period beginning 24 h prior to challenge; 12 h following acute challenge, mice were either tested in a 6-min forced swim test, or served as home cage controls (n = 9 per group). In Experiment 2, the protocol was repeated, but with the aim of assessing c-Fos expression in brainstem serotonergic neurons, assessed 90 min following exposure to forced swim (N = 32; n = 8 per group). In Experiment 1, acute M. vaccae challenge in M. vaccae-immunized mice, relative to vehicle-challenged controls, decreased locomotor activity and core body temperature measured 3 h following challenge, as measured by continuous telemetric recordings, and decreased immobility in the forced swim test measured 12 h following challenge. In Experiment 2, acute M. vaccae challenge in M. vaccae-immunized mice decreased home cage locomotion, in alignment with findings in Experiment 1, as measured by video-based behavioral analysis, and, among mice exposed to the forced swim test, increased c-Fos expression in subsets of serotonergic neurons within the dorsal raphe nucleus (DR) measured 13.5 h following challenge. Together, these data are consistent with the hypothesis that acute peripheral immune activation with a heat-killed preparation of M. vaccae transiently induces mild hypothermia in association with suppression of locomotor activity, activates subsets of serotonergic neurons in the DR, and induces antidepressant-like behavioral responses.
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    Differential effects of exposure to low-light or high-light open-field on anxiety-related behaviors: Relationship to c-Fos expression in serotonergic and non-serotonergic neurons in the dorsal raphe nucleus
    (Elsevier, 2007-04-02) Bouwknecht, J. Adriaan; Spiga, Francesca; Staub, Daniel R.; Hale, Matthew W.; Shekhar, Anantha; Lowry, Christopher A.; Psychiatry, School of Medicine
    Serotonergic systems arising from the mid-rostrocaudal and caudal dorsal raphe nucleus (DR) have been implicated in the facilitation of anxiety-related behavioral responses to anxiogenic drugs or aversive stimuli. In this study we attempted to determine a threshold to engage serotonergic neurons in the DR following exposure to aversive conditions in an anxiety-related behavioral test. We manipulated the intensity of anxiogenic stimuli in studies of male Wistar rats by leaving them undisturbed (CO), briefly handling them (HA), or exposing them to an open-field arena for 15-min under low-light (LL: 8–13 lx) or high-light (HL: 400–500 lx) conditions. Rats exposed to HL conditions responded with reduced locomotor activity, reduced time spent exploring the center of the arena, a lower frequency of rearing and grooming, and an increased frequency of facing the corner of the arena compared to LL rats. Rats exposed to HL conditions had small but significant increases in c-Fos expression within serotonergic neurons in subdivisions of the rostral DR. Exposure to HL conditions did not alter c-Fos responses in serotonergic neurons in any other DR subdivision. In contrast, rats exposed to the open-field arena had increased c-Fos expression in non-serotonergic cells throughout the DR compared to CO rats, and this effect was particularly apparent in the dorsolateral part of the DR. We conclude that exposure to HL conditions, compared to LL conditions, increased anxiety-related behavioral responses in an open-field arena but this stimulus was at or below the threshold required to increase c-Fos expression in serotonergic neurons.