Toxicity and Sublethal Effects of Piper hispidinervum Essential Oil on Behavioral and Physiological Responses of Sitophilus zeamais Populations.

This study aimed to evaluate the toxicity of Piper hispidinervum essential oil (PHEO) against 11 Brazilian populations of Sitophilus zeamais (Coleoptera: Curculionidae). The effects of sublethal doses of PHEO on the behavior (walking and flying), respiration, and population growth (ri) of the insect populations were investigated. PHEO toxicity was determined through concentration-mortality bioassays, with mortality curves established using increasing PHEO concentrations ranging from 140.00 to 1000.00 µL kg-1. Behavior was evaluated based on walking distance, walking time, walking speed, walking time proportion, flight height, and flight takeoff success. Respiration was measured via the respiratory rate, while population growth (ri) was assessed through the instantaneous growth rate. All 11 populations of S. zeamais were susceptible to PHEO, showing no signs of resistance. The populations exhibited varying behavioral and physiological responses to sublethal exposure to PHEO, indicating different mitigation strategies. The results confirm that PHEO possesses insecticidal potential for controlling S. zeamais populations. However, the observed behavioral and physiological responses should be considered when establishing control measures in pest management programs for stored products.

Pharmacological Manipulation of Corticotropin-Releasing Factor Receptors in the Anterior and Posterior Subregions of the Insular Cortex Differently Affects Anxiety-Like Behaviors in the Elevated Plus Maze in Rats.

Neuroimaging data in humans and neurobiological studies in rodents have suggested an involvement of the insular cortex (IC) in anxiety manifestations. However, the local neurochemical mechanisms involved are still poorly understood. Corticotropin-releasing factor (CRF) neurotransmission has been described as a prominent neurochemical mechanism involved in the expression of anxiety-like behaviors, but the brain sites related are poorly understood. Additionally, several findings indicate that control of physiological and behavioral responses by the IC occurs in a site-specific manner along its rostrocaudal axis. Thus, this study is aimed at evaluating the effect of CRF receptor agonism and antagonism within the anterior and posterior subregions of the IC in controlling anxiety-related behaviors in the elevated plus maze (EPM). For this, independent groups (six groups) of animals received bilateral microinjections of vehicle, the selective CRF1 receptor antagonist CP376395, or CRF into either the anterior or posterior subregions of the IC. Ten minutes later, the behavior in the EPM was evaluated for five minutes. Treatment of the anterior IC with CP376395, but not with CRF, increased the time and number of entries into the open arms of the EPM. CRF, but not the CRF1 receptor antagonist, microinjected into the posterior IC also increased exploration of the EPM open arms. Taken together, these data indicate that CRFergic neurotransmission in the anterior IC is involved in the expression of anxiety-related behaviors in the EPM. This neurochemical mechanism does not seem to be activated within the posterior IC during exposure to the EPM, but the effects caused by CRF microinjection indicate that activation of CRF receptors in this IC subregion might evoke anxiolytic-like effects.