Biology subjects

Giannoni Guzman, M. A.

Publications and source records attributed to Giannoni Guzman, M. A..

3 recordsLinked to original sources

bioRxiv2025

Photoperiodic Regulation of SK Channels in Dorsal Raphe Serotonin Neurons

Day length, or seasonal photoperiod, shapes mood and affective behaviors but the neural mechanisms underlying these effects are still being defined. Serotonin neurons of the dorsal raphe nucleus (DRN) are critical regulators of affective behaviors and photoperiod modulates their excitability and ongoing activity. Here, we investigated the influence of seasonal photoperiod on the function and expression of small conductance calcium-activated potassium (SK) channels which mediate the afterhyperpolarizing potential (AHP) in dorsal raphe serotonin neurons. Building on previous work demonstrating that photoperiod modulates serotonergic excitability and behavior, we hypothesized that day length influences SK channel activity, thereby contributing to differences in neuronal excitability observed between Long, Equinox, and Short photoperiod conditions. Using multi-electrode array recording of DRN slices we found a significant dose-dependent increase in spike rate to the application of the SK channel inhibitor apamin, indicating that SK channels indeed influence the spike rate of dorsal raphe serotonin neurons. In addition, DRN neurons in slices from Long photoperiod mice exhibited less pronounced responses to apamin relative to those from Short photoperiod mice, suggesting reduced function or expression of SK channels in Long photoperiod. Indeed, whole-cell recordings demonstrated that SK channel-mediated AHP currents were reduced in Long photoperiod mice. However, there were no significant differences in expression levels of the SK3 subunit (Kcnn3) in DRN serotonin neurons across photoperiod conditions as determined by single molecule fluorescence in situ hybridization. Overall, these findings indicate that photoperiod modulates SK channel function in DRN serotonin neurons likely at a post-transcriptional level. This study advances our understanding of how seasonal cues influence intrinsic neuronal properties and provides a mechanistic link between photoperiod, serotonergic excitability, and mood-related behaviors. The identification of SK channels as modulators of photoperiodic effects may offer novel therapeutic targets for mood disorders associated with dysregulated serotonin signaling.

neuroscience↗

bioRxiv2020

The Role of Colony Temperature in the Entrainment of Circadian Rhythms of Honey Bee Foragers

Honey bees utilize their circadian rhythms to accurately predict the time of day. This ability allows foragers to remember the specific timing of food availability and its location for several days. Previous studies have provided strong evidence toward light/dark cycles being the primary Zeitgeber for honey bees. Work in our laboratory described large individual variation in the endogenous period length of honey bee foragers from the same colony and differences in the endogenous rhythms under different constant temperatures. In this study, we further this work by examining temperature inside the honey bee colony. By placing temperature and light data loggers at different locations inside the colony we measured temperature at various locations within the colony. We observed significant oscillations of temperature inside the hive, that show seasonal patterns. We then simulated the observed temperature oscillations in the laboratory and found that using the temperature cycle as a Zeitgeber, foragers present large individual differences in the phase of locomotor rhythms with respect to temperature. Moreover, foragers successfully synchronize their locomotor rhythms to these simulated temperature cycles. Advancing the cycle by six hours, resulted in changes in the phase of activity in some foragers in the assay. The results shown in this study highlight the importance of temperature as a potential Zeitgeber in the field. Future studies will examine the possible functional and evolutionary role of the observed phase differences of circadian rhythms.

animal behavior and cognition↗

bioRxiv2020

Shift work dynamics and division of labor: honeybee foraging and fanning tasks

In complex societies common social needs such as vigilance, care giving, resource gathering, and production are attended around the clock. In humans, these services are constantly provided using a shift work strategy where different individuals, or groups of individuals perform their tasks at different times of the day. However, shift work strategy in job organization in other social organisms remains unclear. Previous studies in honeybees for two jobs support shift work for only pollen foragers and not for nursing behavior. Here we examined shift work dynamics for three types of jobs performed by honeybee foragers. Specifically, we studied pollen foragers, non-pollen foragers and bees fanning at the entrance of the colony, a job important for orientation and temperature control. Major features of the observed shift work were: 1) individuals can be divided into early and late shifts; 2) there are constant workers; 3) based on job, shift work is performed by fewer or greater number of individuals; 4) shift work of an individual is plastic and may change with age; 5) foraging and fanning shifts are coupled yet dissociable. This study adds to the findings that shift work is not exclusive to modern human societies and that a natural form of shift work exists in honeybees. These results suggest that shift work in honeybees is a feature of worker division of labor. Future studies aiming to further understand the structure, function and mechanism of this natural form of shift work in honey bees not only could have an impact on agriculture but also may provide insight into alternative forms of shift work strategies that may reduce the various health problems associated with shift work in humans.

animal behavior and cognition↗