Caffeine ingestion by rats increases noradrenaline turnover and results in self-biting

Animal Models of Self-Injurious Behavior: An Update

Although self-injurious behavior is a common comorbid behavior problem among individuals with neurodevelopmental disorders, little is known about its etiology and underlying neurobiology. Interestingly, it shows up in various forms across patient groups with distinct genetic errors and diagnostic categories. This suggests that there may be shared neuropathology that confers vulnerability in these disparate groups. Convergent evidence from clinical pharmacotherapy, brain imaging studies, postmortem neurochemical analyses, and animal models indicates that dopaminergic insufficiency is a key contributing factor. This chapter provides an overview of studies in which animal models have been used to investigate the biochemical basis of self-injury and highlights the convergence in findings between these models and expression of self-injury in humans.

Effect of Caffeine Chronically Consumed During Pregnancy on Adenosine A1 and A2A Receptors Signaling in Both Maternal and Fetal Heart from Wistar Rats

Background: Caffeine is the most widely consumed psychoactive substance in the world, even during pregnancy. Its stimulatory effects are mainly due to antagonism of adenosine actions by blocking adenosine A₁ and A_2A receptors. Previous studies have shown that caffeine can cross the placenta and therefore modulate these receptors not only in the fetal brain but also in the heart. Methods: In the present work, the effect of caffeine chronically consumed during pregnancy on A₁ and A_2A receptors in Wistar rat heart, from both mothers and their fetuses, were studied using radioligand binding, Western-blotting, and adenylyl cyclase activity assays, as well as reverse transcription polymerase chain reaction. Results: Caffeine did not significantly alter A₁R neither at protein nor at gene expression level in both the maternal and fetal heart. On the contrary, A_2AR significantly decreased in the maternal heart, although mRNA was not affected. Gi and Gs proteins were also preserved. Finally, A₁R-mediated inhibition of adenylyl cyclase activity did not change in the maternal heart, but A_2AR mediated stimulation of this enzymatic activity significantly decreased according to the detected loss of this receptor. Conclusions: Opposite to the downregulation and desensitization of the A₁R/AC pathway previously reported in the brain, these results show that this pathway is not affected in rat heart after caffeine exposure during pregnancy. In addition, A_2AR is downregulated and desensitized in the maternal heart, suggesting a differential modulation of these receptor-mediated pathways by caffeine.

Animal models of self-injurious behaviour: an overview

Self-injurious behaviour is highly prevalent in neurodevelopmental disorders. Interestingly, it is not restricted to any individual diagnostic group. Rather, it is exhibited in various forms across patient groups with distinct genetic defects and classifications of disorders. This suggests that there may be shared neuropathology that confers vulnerability. Convergent evidence from clinical pharmacotherapy, brain imaging studies, postmortem neurochemical analyses, and animal models indicates that dopaminergic insufficiency is a key culprit. This chapter provides an overview of studies in which animal models have been used to investigate the biochemical basis of self-injury, and highlights the convergence in findings between these models and expression of self-injury in humans.

Caffeinated coffee enhances co-operative behavior in the Mixed Motive Game in healthy volunteers

Caffeinated drinks are commonly consumed in social gatherings. However, their effects on social behavior remain unclear. The present study examined the effects of caffeinated coffee on antidepressant-related co-operative behavior. Seventy-seven low-caffeine users took part in a randomized, double-blind, cross-over study of single dose of caffeinated coffee (150 mg caffeine) and decaffeinated coffee (9 mg caffeine) with at least a 3-day washout period. In each session, participants were asked to imagine a fictitious person and play the Mixed Motive Game with that person 45 min after coffee consumption. Heart rate, blood pressure, and state moods were measured at baseline and at 45 min post-coffee consumption. After caffeinated coffee, participants exhibited significantly higher blood pressure. They also allocated significantly fewer scores to themselves and sent significantly more sadness message during the game. These results suggest that caffeinated coffee may help to improve social support and depressive symptoms.

Effects of prolonged caffeine consumption on cardiac contractile function in rats

The purpose of the study was to explore effects of prolonged caffeine administration on the contractile function and myocardial energy metabolites of the isolated rat heart. Caffeine treatment for 1 week (10 mg/kg, i.p., twice a day) was followed by unchanged pump function of the isolated heart, but reduced maximal left ventricular (LV) systolic pressure by 14% (p < 0.05). Caffeine consumption during 8-9 weeks (0.1% water solution) was also followed by unchanged maximal pump function but increased maximal double product (LV developed pressure multiplied by heart rate) by 23% (p < 0.05). The hearts of caffeine-consumed rats also maintained a higher level of the pump function at a high rate of atrial electrostimulation. The myocardial content of adenosine triphosphate (ATP), creatine phosphate, as well as creatine was slightly but insignificantly increased after caffeine consumption. Results show that in the course of prolonged caffeine treatment, the maximal myocardial contractile function first decreases and then increases, showing adaptation of the heart.

Caffeine increases renal renin secretion in a rat model of genetic heart failure

In a previous study, we showed that caffeine (CAFF) increases basal renin secretion by blocking intrarenal adenosine receptors and, when sympathetic activity is increased, augments renin release in part by blockade of brain adenosine receptors, leading to increased central sympathetic tone. The purpose of this study was to investigate the effects of CAFF treatment on neurohumoral status and heart performance in experimental heart failure. Two series of experiments were performed. First, the effects of CAFF (10 mg/kg +150 microg/min over 40 min) on heart performance (time-pressure variables) and neurohumoral status were studied in conscious, 9-month-old Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHRs), and spontaneously hypertensive heart failure (SHHF/Mcc-fa(cp) rats. Second, caffeine (0.1% in drinking water) was given for 10 days to 14-month-old SHHF/Mcc-fa(cp) rats, and cardiac performance, renal function, and neurohumoral status determined in vivo. CAFF infusion increased heart rate, left ventricular peak systolic pressure, and workload in hypertensive (SHRs and SHHF), but not in normotensive (WKY) animals and had no effects on cardiac contractility in all three strains. CAFF increased plasma renin activity (PRA), norepinephrine (NE), and epinephrine (E) levels in all three strains [treatment effect, p<0.001, 2F analysis of variance (ANOVA)], and these effects were greater in hypertensive (SHRs and SHHF) animals as compared with normotensive WKY rats (p<0.015). Ten-day CAFF treatment in 14-month-old SHHF did not change measured cardiac time-pressure variables, or hemodynamic or renal excretory function parameters that can affect renin secretion. However, CAFF treatment significantly increased renal renin secretion (71.1+/-19.2 vs. 9.5+/-5.8 ng Ang I/h/min/kg for caffeine and control group, respectively; p<0.01). In summary, acute administration of CAFF increases workload, but has no effects on cardiac contractility in conscious SHHF rats. The cardiac effects are accompanied by increased renin release and NE and E plasma levels. Moreover, this study provides the first evidence that short-term caffeine consumption increases renal renin secretion in heart failure, an effect most likely due to the blockade of intrarenal adenosine receptors. It is possible that long-term activation of neurohumoral mechanisms by CAFF could have adverse effects in heart failure.

Caffeine and the olfactory bulb

Caffeine, a popular CNS stimulant, is the most widely used neuroactive drug. Present in coffee, tea, chocolate, and soft drinks as well as over-the-counter and prescription medications, it influences millions of users. This agent has achieved recent notoriety because its dependency consequences and addictive potential have been re-examined and emphasized. Caffeine's central actions are thought to be mediated through adenosine (A) receptors and monoamine neurotransmitters. The present article suggests that the olfactory bulb (OB) may be an important site in the brain that is responsible for caffeine's central actions in several species. This conclusion is based on the extraordinarily robust and selective effects of caffeine on norepinephrine (NE), dopamine (DA), and particularly serotonin (5HT) utilization in the OB of mice. We believe that these phenomena should be given appropriate consideration as a basis for caffeine's central actions, even in primates. Concurrently, we review a rich rodent literature concerned with A, 5HT, NE, and DA receptors in the OB and related structures along with other monoamine parameters. We also review a more limited literature concerned with the primate OB. Finally, we cite the literature that treats the dependency and addictive effects of caffeine in humans, and relate the findings to possible olfactory mechanisms.

A dopamine deficiency model of Lesch-Nyhan disease--the neonatal-6-OHDA-lesioned rat

Lesch-Nyhan syndrome is characterized by a deficiency of the enzyme hypoxanthine phosphoribosyl transferase (HPRT), compulsive self-mutilatory behavior (SMB), and a loss of central dopaminergic neurons. In order to model the loss of central dopamine-containing neurons in this developmental disorder, neonatal rat pups 3 days of age were given the neurotoxin 6-OHDA intracisternally to reduce brain dopamine. Accompanying the profound loss of dopamine produced by this treatment was an increase in striatal serotonin content. When these neonatally lesioned rats were challenged as adults with systemically administered L-DOPA or with muscimol administration into substantia nigra reticulata (SNR), SMB was observed, a response not observed in unlesioned rats. Thus, the neonatally lesioned rats exhibit increased susceptibility for SMB. Since a D1-dopamine antagonist blocked the SMB response to L-DOPA, it was proposed that D1-dopamine receptors were critical to this behavioral response. Basic investigations concerning D1-dopamine receptor mechanisms in the lesioned rats have been performed and these are reviewed. The data in the neonatally lesioned rats provide convincing evidence that the absence of central dopaminergic neurons is responsible for at least some of the neurological symptoms of the Lesch-Nyhan syndrome, a finding consistent with data collected in mice with an HPRT deficiency.

Antiparkinsonian effects of caffeine depend upon pavlovian drug conditioning processes

Caffeine induces the antiparkinsonian response of contralateral rotation in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions following exposure to the direct-acting dopamine agonist apomorphine. This effect of caffeine has been attributed to a 'priming' effect of apomorphine which enables the supersensitive dopamine receptors to respond to caffeine and other methylxanthines. These studies, however, did not differentiate between conditioning and pharmacological variables. To resolve this issue, a Pavlovian conditioning procedure was employed in which separate groups of 6-OHDA rats were given 0.05 mg/kg (s.c.) apomorphine treatments paired or unpaired with a test environment. The animals in the paired or conditioning treatment groups subsequently exhibited contralateral rotation when tested with caffeine (10 mg/kg, i.p.), whereas animals in the unpaired or 'priming' treatment groups displayed only enhanced ipsilateral rotation. The activation of the conditioned contralateral rotation by caffeine in the paired group occurred even after the response was suppressed by extinction. This preferential activation following extinction of a previously conditioned drug response by caffeine implicates caffeine mechanisms (e.g. adenosine antagonism) in drug conditioning processes.