Anxiogenic Effects Of Caffeine Research Articles

Caffeine-induced bradycardia, death, and anxiety-like behavior in zebrafish larvae

Caffeine, a major ingredient of coffee and other drinks, causes minimal health problems. However, excessive caffeine intake may induce emotional and cardiac events. Studies on zebrafish larvae are considered useful for understanding drug poisoning because they can be used for multiple simulations. The locomotion (swim distance) of zebrafish larvae exposed to varying concentrations of caffeine was measured using a light–dark test and an automatic video-tracking system. Mortality and heart rates were assessed 4 and 24 h after caffeine exposure and 24 h after caffeine removal. The heart and survival rates were reduced by exposure to caffeine of > 300 mg/L after 24 h in a dose-dependent manner; this was attenuated by caffeine removal at 4 h. Caffeine reduced the heart rate and survival considerably at 1000 mg/L, supporting the notion of caffeine-induced cardiac arrest resulting from bradycardia. The locomotion of zebrafish larvae during six alternating cycles of light–dark exposure was slower during light periods and faster during dark periods; 100–300 mg/L caffeine increased and decreased locomotion during light and dark cycles, respectively, with high inter-cycle reproducibility. Given the anxiogenic effect of caffeine and light preference of zebrafish larvae, caffeine-induced changes in light–dark cycles could provide a new reliable marker for anxiety. Therefore, the “light–dark locomotion test” employed in this study is valuable for research on anxiogenic or anxiolytic substances. The test may allow simultaneous and automatic analysis of the locomotion of many fish under multiple conditions, thereby enabling evaluation of dose–response effects of caffeine.

The Anxiogenic Effects of Caffeine Do Not Potentiate Nicotine Withdrawal in an Elevated Plus Maze Model of Anxiety

Background: Negative effect during withdrawal is associated with tobacco relapse, yet little is known about factors that increase the aversive symptoms of withdrawal. This study explored how caffei...

Aged mice receiving caffeine since adulthood show distinct patterns of anxiety-related behavior

Caffeine is the psychostimulant most consumed worldwide. Anxiogenic effects of caffeine have been described in adult animals with controversial findings about its anxiogenic potential. Besides, the effects of caffeine on anxiety with aging are still poorly known. In this study, adult mice (6months old) started to receive caffeine (0.3 and 1.0mg/mL, drinking water) during 12–14months only in the light cycle and at weekdays. The open field (OF) and elevated plus maze (EPM) testing were used to determine the effects of caffeine on anxiety-related behavior in adult and aged mice (18–20months old). Because aging alters synaptic proteins, we also evaluated SNAP-25 (as a nerve terminals marker), GFAP (as an astrocyte marker) and adenosine A1 and A2A receptors levels in the cortex. According to the OF analysis, caffeine did not change both hypolocomotion and anxiety with aging. However, aged mice showed less anxiety behavior in the EPM, but after receiving caffeine (0.3mg/mL) during adulthood they were anxious as adult mice. While SNAP-25 and adenosine A2A receptors increased with aging, both GFAP and adenosine A1 receptors were not affected. Caffeine at moderate dose prevented the age-related increase of the SNAP-25, with no effect on adenosine A2A receptors. The absence of effect for the highest dose suggests that tolerance to caffeine may have developed over time. Aged mice showed high responsiveness to the OF, being difficult to achieve any effect of caffeine. On the other hand this substance sustained the adult anxious behavior over time in a less stressful paradigm, and this effect was coincident with changes in the SNAP-25, suggesting the involvement of this synaptic protein in the ability of caffeine to preserve changes related to emotionality with aging.

Emotional and Physical Distress Relief Using a Novel Endorphinergic Formulation

While the endogenous opioid system has generally been associated with regulation of pain, it also modulates the experience of distress and may play a central role in many psychiatric and neurodevelopmental disorders. Decades of preclinical research on the analgesic effects of endogenous opioids, i.e., endorphins, suggests that opioid receptors have plastic bimodal (inhibitory/excitatory) properties that may explain conflicting findings in clinical research. An exploratory study with 60 healthy volunteer participants, using a cold pressor-induced pain paradigm, found evidence that a combination of a nutraceutical agent that enhances endorphin release (Endorphin Enhancer) with one that switches opioid receptors from an excitatory to inhibitory mode (Opioid Receptor Switcher) not only increases pain tolerance but also reduces emotional and physical distress. This discovery led to clinical application of a critically formulated endorphinergic treatment in 203 case studies over a two-year period. Findings revealed the remarkable clinical efficacy and safety of this treatment in the relief of chronic emotional and physical distress, including anxiety, anger, depression, cravings, and hyperalgesia, as well as enhancement of well-being, productivity, mental clarity, relationships, and an adaptive response to life’s stresses. These studies provide new insights into the role of endogenous opioid system imbalances in the development, treatment, and prevention of dysfunctional emotional and physical distress. We postulate that an Endorphinergic Distress Syndrome (EDS) consists of abnormal endorphin levels together with opioid receptors predominately in their excitatory mode. EDS may account for many core distress symptoms associated with chronic anxiety, addictions, pain, as well as affective personality, autism spectrum, attention-deficit, and distress-related medical problems. Our research has led to new endorphinergic formulations, combining Endorphin Enhancers, such as caffeine, with Opioid Receptor Switchers, such as n-acetylcysteine, for the relief of emotional and physical distress. Our studies also provide a novel method to reverse the anxiogenic effects of caffeine and related hyperexcitatory substances.

Effect of social isolation on behavioral parameters and sensitivity of rats to morphine and caffeine.

Social isolation is a stress factor increasing animal anxiety and impairing food-reinforced instrumental learning. Social isolation modulates sensitivity to psychoactive substances: it potentiated the depressive and analgesic effects of morphine, but attenuated the activating and anxiogenic effects of caffeine. These behavioral changes and changes in sensitivity to psychoactive agents can be explained by a well-known phenomenon of activation of the endogenous opioid system during stress.

Caffeine-Induced Increases in the Brain and Plasma Concentrations of Neuroactive Steroids in the Rat

The effects of caffeine, a naturally occurring stimulant, on the brain and plasma concentrations of neuroactive steroids were examined in the rat. A single intraperitoneal injection of caffeine induced dose- and time-dependent increases in the concentrations of pregnenolone, progesterone, and 3α-hydroxy-5α-pregnan-20-one (allopregnanolone) in the cerebral cortex. The increases were significant at a caffeine dose of 25 mg/kg and greatest (+188, +388, and +71%, respectively) at a dose of 100 mg/kg in rats killed 30 min after caffeine administration. Caffeine also increased the plasma concentrations of pregnenolone and progesterone with a dose-response relation similar to that observed in the brain, whereas the caffeine-induced increase in the plasma concentration of allopregnanolone was maximal at a dose of 50 mg/kg. Caffeine increased the plasma concentration of corticosterone, but it had no effect on the brain or plasma concentrations of 3α,21-dihydroxy-5α-pregnan-20-one and dehydroepiandrosterone. Moreover, the brain and plasma concentrations of pregnenolone, progesterone, and allopregnanolone were not affected by caffeine in adrenalectomized-orchiectomized rats. These results suggest that neuroactive steroids may modulate the stimulant and anxiogenic effects of caffeine.

Caffeine-induced anxiogenesis: The role of adenosine, benzodiazepine and noradrenergic receptors

The purpose of this study was to determine the mechanism by which caffeine increases anxiety. Rats were tested in the social interaction test of anxiety after administration of caffeine (20 or 40 mg/kg) alone or in combination with various compounds. In order to investigate the role of adenosine receptors, caffeine was given in combination with 2-chloroadenosine (0.1 and 1 mg/kg). To investigate the role of benzodiazepine receptors, chlordiazepoxide (5 mg/kg), a benzodiazepine antagonist, flumazenil (RO 15-1788, 1 and 10 mg/kg) and a triazolobenzodiazepine U-43,465 (32 mg/kg) were used. Finally, an alpha 2-receptor agonist, clonidine (0.1 and 0.025 mg/kg) and a beta-adrenoceptor antagonist, DL-propranolol (5 mg/kg), were used to study the role of noradrenergic systems in the effects of caffeine. Caffeine (20 and 40 mg/kg) reduced the time spent in social interaction and this effect was antagonized by chlordiazepoxide, U-43,465 and DL-propranolol, but not by flumazenil, 2-chloroadenosine or clonidine. It was therefore concluded that the anxiogenic effect of caffeine was unlikely to be due to its effects at adenosine or benzodiazepine receptors. It is suggested that the reversal of caffeine's effects by chordiazepoxide may have been "functional," i.e., merely a cancellation of two opposite effects. It is discussed whether the reversal of caffeine's effects by propranolol and U-43,465 are functional, or reflect a noradrenergic site of action.