Addiction is a complex process in which behavioral sensitization may be an important component. While the behavioral effects of sensitization are well established, the intricate neurobiology of the phenomenon is still largely unknown. Dopamine systems mediate the induction of behavioral sensitization in adult rats, but there is a large amount of evidence showing that other neurotransmitter systems also modulate the induction process. For example, the α1b-adrenergic and 5-HT2A receptor systems are known to modulate the sensitized responding of adult rats, but the roles that these receptor systems play in the induction and expression of behavioral sensitization during the preweanling period has yet to be investigated. Therefore, the purpose of this thesis was to determine whether the serotonergic and adrenergic receptor systems mediate the induction and/or expression of cocaine-induced one-trial behavioral sensitization in preweanling rats. I used a novel approach to address this question, as the receptors of interest were “protected” from the alkylating effects of EEDQ (an irreversible nonselective receptor antagonist) by prior treatment with selective antagonist drugs. More specifically, rats were given ritanserin (a serotonergic receptor antagonist), prazosin (an adrenergic receptor antagonist), or a combination of the two drugs prior to an injection of EEDQ. To study the induction of behavioral sensitization, this series of injections was administered on PD 18 (24 h before the pretreatment injection of cocaine). To study the expression of behavioral sensitization, the injections were administered on PD 20, which was the day between the drug pretreatment day and the test day. In all experiments, the test day (i.e., the day on which the challenge dose of cocaine was given) was on PD 21. Control experiments were performed for both the induction and expression paradigms in order to determine whether prazosin and ritanserin independently affected sensitization. Results showed that the receptor inactivation caused by EEDQ blocked both the induction and expression of cocaine-induced one-trial behavioral sensitization. Importantly, administering prazosin and ritanserin did not protect the induction of the sensitized locomotor response, which suggests that serotonergic and adrenergic receptors do not mediate cocaine-induced one-trial behavioral sensitization in preweanling rats. This conclusion should be tempered, however, because co-administration of prazosin and ritanserin affected the locomotor activity and sensitized responding of cocaine-treated rats independent of the actions of EEDQ. Considering both past and present results, the most harmonious conclusion is that multiple receptor systems (i.e., dopaminergic, serotonergic, adrenergic, etc.) work in unison to produce the complex phenomenon of behavioral sensitization.

Pagrindinis tyrimo tikslas – įvertinti ir palyginti skirtingo selektyvumo alfa1 adrenoreceptorių antagonistų (prazosino ir tamsulozino) farmakologinį poveikį izoliuotoms laboratorinių jūrų kiaulyčių kraujagyslėms eksperimentiniame modelyje in vitro. Tyrimams pasirinkti laboratoriniai gyvūnai – dėl tinkamo kraujagyslių spindžio ne jaunesni nei 8 – 12 savaičių amžiaus linijinių jūrų kiaulyčių patinėliai. Vaistų poveikis buvo vertinamas izoliuotoms kraujagyslėms – jų aortoms ir inkstų arterijoms. Eksperimentas atliktas naudojant organų vonelę PTK23 – 220 Pharmacology Kit (ADInstruments, Jungtinė Karalystė). Duomenys registruoti ,,LabChart“ programine įranga. Prazosino ir tamsulozino poveikiui įvertinti kraujagyslės buvo veikiamos atitinkamai 10 nM, 100 nM, 1000 nM ir 1 nM, 10 nM, 100 nM koncentracijų tirpalais. Prazosino 10 nM, 100 nM, 1000 nM koncentracijos sukėlė aortos atsipalaidavimą atitinkamai per 0,043±0,030 g, 0,083±0,022 g ir 0,195±0,040 g jėgą, inkstų arterijos – per 0,065±0,013 g, 0,075±0,024 g ir 0,173±0,026 g jėgą. Tamsulozino 1 nM, 10 nM, 100 nM koncentracijos sukėlė aortos atsipalaidavimą atitinkamai per 0,015±0,012 g, 0,080±0,018 g, 0,133±0,039 g jėgą, inkstų arterijos – per 0,025±0,020 g, 0,078±0,035 g ir 0,123±0,037 g jėgą. Vertinant aortos dilataciją, gauti statistiškai patikimi skirtumai tarp visų prazosino (10 nM, 100 nM, 1000 nM) koncentracijų. Inkstų arterijos atsipalaidavimo vertinime nenustatytas statistiškai patikimas skirtumas tarp 10 nM ir 100... [toliau žr. visą tekstą] / The main aim of the research was to evaluate and compare the pharmacological influence of α1 adrenoreceptor antagonists (prazosin and tamsulosin) of different selectivity over the isolated laboratorial guinea pig blood vessels in experimental model in vitro. The male linear guinea pigs, not younger than 8-12 weeks, were selected as the object of the investigation because of their relevant blood vessel size. The influence of medicine over isolated blood vessels, aortas and kidney arteries, was evaluated. The experiment was carried out by using the utensil for organs PTK23- 220 Pharmacology Kit (AD instruments, United Kingdom). The data is registered with the software “LabChart”. The blood vessels were processed with the concentrated solutions 10 nM, 100 nM, 1000 nM, and 1 nM, 10 nM, 100 nM, accordingly, to evaluate the influence of prazosin and tamsulosin. The concentrations of prazosin 10 nM, 100 nM, 1000 nM caused the ease of aorta, accordingly, in 0,043±0,030g, 0,083±0,022g, and 0,195±0,040g power, the ease of kidney artery - in 0,065±0,013g, 0,075±0,024g, and 0,173±0,026g power. The concentrations of tamsulosin 1 nM, 10 nM, 100 nM caused the ease of aorta, accordingly, in 0,015±0,012g, 0,080±0,018g, 0,133±0,039 power, the ease of kidney artery – in 0,025±0,020g, 0,078±0,035g, and 0,123±0,037g power. Aming to estimate the dilation of aorta, statistically reliable differences among all concentrations of prazosin (10 nM, 100 nM, 1000 nM) were acquired. In the estimation of... [to full text]

Thesis (Ph.D.)--Uniformed Services University of the Health Sciences, 2006 / Typescript (photocopy)

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Previous studies show that prazosin, an α1-adrenergic receptor antagonist, decreases alcohol drinking in animal models of alcohol use and dependence and in alcohol-dependent men. These studies extended previous findings by using a paradigm that allows for separate assessment of prazosin on motivation to seek versus consume ethanol or sucrose in selectively bred rats given acute or chronic prazosin treatment. Methods: Alcohol-preferring P rats were trained to complete an operant response that resulted in access to either 2% (Exp. 1) or 1% (Exp.2) sucrose or 10% ethanol. In Experiment 1, a 4-week consummatory testing phase consisted of rats bar-pressing to “pay” a specified amount up front to gain access to unlimited ethanol (or sucrose) for a 20-minute period. A 4-week appetitive testing phase examined how much the rats would bar-press for ethanol in an extinction session when no reinforcer could be obtained. In Experiment 2, during testing, the response requirement was dropped to a 1 and daily session cycles of drug (3 weeks/ 14 sessions from Tues to Fri) or vehicle (2 weeks/ 9 sessions from Tues to Fri) treatment were alternated per drug dose for a total of 3 drug doses (3 cycles) per rat. After each drug cycle, a single non-reinforced extinction session was conducted with no drug ‘on board’ and no reinforcer access. On test days, rats were given IP injections of either vehicle or one of three doses of prazosin (Exp 1: 0.5, 1.0, 1.5 mg/kg; Exp 2: 0.25, 0.5, 1.0 mg/kg; balanced design; -30 min). Results: In Experiment 1, prazosin significantly decreased ethanol-seeking at all doses tested. The highest dose decreased ethanol intake and increased the latency to first lever-press and first lick. Sucrose-seeking and intake were decreased by the same doses of prazosin. In Experiment 2, prazosin significantly decreased reinforcer-seeking at the lowest and highest doses while ethanol intake was not decreased by prazosin. Conversely, sucrose-seeking was decreased at the highest dose of prazosin tested while sucrose consumption was decreased by all doses. Latency to lever-press for sucrose was increased by the lowest dose of prazosin compared to vehicle. Conclusions: These findings extend previous research and indicate that prazosin decreases motivation to seek ethanol and sucrose. The specificity of prazosin on different behaviors and over different reinforcers suggests that these findings are not due to prazosin-induced motor-impairment or malaise. These data suggest that prazosin may work by decreasing the reinforcing properties of reinforcers in general.

Aim: The general aim of this research is development and evaluation of novel methods for predicting active transport over the human blood-brain-barrier (BBB), while this project specifically aims to i) review the literature and select suitable methods and substrates, ii) develop models for determining in vitro kinetic properties of selected compounds, analyze the in vitro data using the developed models and to use Maximum Transport Activity (MTA) approach (Karlgren et al., 2012), iii) perform Physiology Based Pharmacokinetic (PBPK) modelling and compare to in vivo literature data. Background: Drug permeation to the brain through blood circulation is primarily limited by blood-brain barrier (BBB), due to existence of tight junctions in endothelial cells of blood vessels as well as active efflux and influx transporters in the barrier. Toxicity and CNS related side effects can be caused by peripheral targeted drugs crossing BBB. Hence, prediction of BBB permeability and estimation of drug concentration in the brain tissue are challenging in drug discovery. To resolve this, estimating the human BBB permeability using improved in vitro and in silico predictive models can be a facilitator. Methods: In vitro data provided by the Drug Delivery research group was used to develop in vitro predictive models for BBB penetration of Verapamil, Risperidone, and Prazosin using R-studio 1.2.5. The MTA approach was adjusted for extrapolation of BBB in vitro transporter activity to in vivo condition. For PBPK modelling, we took advantage of PK-Sim® to simulate drug disposition and time profile of Risperidone in human and animal species. Results: It was shown that MDR1 is the major transporter for efflux transport of Prazosin and Risperidone in brain while both BCRP and MDR1 have similar impact on transport of Verapamil. Furthermore, it was presented in PBPK models that the predicted brain concentration of Risperidone increases in rat and nonhuman primate (NHP) when MDR1 And BCRP are knocked out while the brain concentration of Risperidone in dog is not affected by expression level of the efflux transporters. Conclusion: Both MDR1 and BCRP are contributing in efflux transport of Verapamil, Risperidone, and Prazosin across the BBB. Additionally, expression of the efflux transporters shown to have an impact on brain exposure of Risperidone in animal PBPK models.

Posttraumatic stress disorder is a debilitating anxiety disorder that can develop in the aftermath of a traumatic or life–threatening event involving extreme horror, intense fear or bodily harm. The disorder is typified by a symptom triad consisting of re–experiencing, hyperarousal and avoidance symptoms. Approximately 15–25% of trauma–exposed individuals go on to develop PTSD, depending on the nature and severity of the trauma. Although dysfunctional adaptive responses exist in multiple neurobiological pathways in the disorder, e.g. glutamate, GABA, glucocortocoids and serotonin, the noradrenergic system is particularly prominent and represents an important pharmacological target in attempts at preventing the development of PTSD posttrauma. However, current literature shows opposing and conflicting results regarding the effect of selective noradrenergic agents in memory processing, and the effect of modulation of selective noradrenergic receptors are spread over diverse protocols and paradigms of learning and fear also employing different strains of animals. Fear conditioning is a behavioural paradigm that uses associative learning to study the neural mechanisms underlying learning, memory and fear. It is useful in investigating the underpinnings of disorders associated with maladaptive fear responses. Performing fear conditioning experiments with the aim of applying it to an animal model of PTSD, and relating these behavioural responses to a defined neural mechanism, will assist both in the elucidation of the underlying pathology of the disease, as well as the development of more effective treatment. This project has set about to re–examine the diverse and complex role of noradrenergic receptors in the conditioned fear response with relevance to PTSD. To the best of my knowledge, this study represents the first attempt at studying a range of noradrenergic compounds with diverse actions and their ability to modify conditioned fear in a single animal model. This work thus introduces greater consistency and comparative relevance not currently available in the literature, and will also provide much needed pre–clinical evidence in support of treatment strategies targeting the noradrenergic system in the prevention of PTSD posttrauma. The first objective of this study was to set up and validate a passive avoidance fear conditioning protocol under our laboratory conditions using the Gemini Avoidance System. The noradrenergic system plays a prominent role in memory consolidation and fear conditioning, while administration of –adrenergic blockers, such as propranolol, have been shown to abolish learning and fear conditioning in both humans and animals. Propranolol has also demonstrated clinical value in preventing the progression of acute traumatic stress syndrome immediately posttrauma to full–blown PTSD. To confer predictive validity to our model, the centrally active –adrenergic antagonist, propranolol, and the non–centrally acting –adrenergic antagonist, nadolol, were administered to Wistar rats after passive avoidance fear conditioning training in the Gemini Avoidance System. Wistar rats were used because of their recognised enhanced sensitivity to stress. Evidence from this pilot study confirmed that propranolol 10 mg/kg significantly inhibits the consolidation of learned fear in rats, whereas nadolol is ineffective. This effectively validated our protocol and the apparatus for further application in this study and also confirmed the importance of a central mechanism of action for –adrenoceptor blockade in the possible application of these drugs in preventing the development of PTSD posttrauma. The second objective of this study was to investigate the role of 1–, 2–, 1–, and 2–receptors in a conditioned fear passive avoidance paradigm. This was done in order to investigate how selective pharmacological modulation of these receptors may modify the conditioned fear response, and whether any of these receptor systems might exert opposing effects in passive fear conditioning. Various centrally active noradrenergic agents were employed over a 3–tiered dose response design, including the 1–antagonist, prazosin, the 2–agonist, guanfacine, the 2–antagonist, yohimbine, the 1–antagonist, betaxolol and the 2–antagonist ICI 118551. The effect of post–exposure administration of these drugs on conditioned fear was compared to that of propranolol 10 mg/kg. Selected doses of betaxolol (10 mg/kg) and ICI 118551 (1 mg/kg) attenuated fear conditioning to an extent comparable to propranolol, as did prazosin (0.1 mg/kg). Yohimbine tended to boster fear learning at all doses tested, albeit not significantly, while guanfacine did not produce any significant effect on memory retention at any of the doses studied. This latter observation was surprising since yohimbine tended to bolster fear conditioning while earlier studies indicate that 2–agonism impairs conditioned fear. Concluding, this study has conferred validity to our passive avoidance model and has provided greater insight into the separate roles of noradrenergic receptors in contextual conditioned fear learning. The study has provided supportive evidence for a key role for both 1– and 2–antagonism, as well as 1–antagonism, in inhibiting fear memory consolidation and hence as viable secondary treatment options to prevent the development of PTSD posttrauma. However, further study is required to delineate the precise role of the 2–receptor in this regard. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2012.

Posttraumatic stress disorder is a debilitating anxiety disorder that can develop in the aftermath of a traumatic or life–threatening event involving extreme horror, intense fear or bodily harm. The disorder is typified by a symptom triad consisting of re–experiencing, hyperarousal and avoidance symptoms. Approximately 15–25% of trauma–exposed individuals go on to develop PTSD, depending on the nature and severity of the trauma. Although dysfunctional adaptive responses exist in multiple neurobiological pathways in the disorder, e.g. glutamate, GABA, glucocortocoids and serotonin, the noradrenergic system is particularly prominent and represents an important pharmacological target in attempts at preventing the development of PTSD posttrauma. However, current literature shows opposing and conflicting results regarding the effect of selective noradrenergic agents in memory processing, and the effect of modulation of selective noradrenergic receptors are spread over diverse protocols and paradigms of learning and fear also employing different strains of animals. Fear conditioning is a behavioural paradigm that uses associative learning to study the neural mechanisms underlying learning, memory and fear. It is useful in investigating the underpinnings of disorders associated with maladaptive fear responses. Performing fear conditioning experiments with the aim of applying it to an animal model of PTSD, and relating these behavioural responses to a defined neural mechanism, will assist both in the elucidation of the underlying pathology of the disease, as well as the development of more effective treatment. This project has set about to re–examine the diverse and complex role of noradrenergic receptors in the conditioned fear response with relevance to PTSD. To the best of my knowledge, this study represents the first attempt at studying a range of noradrenergic compounds with diverse actions and their ability to modify conditioned fear in a single animal model. This work thus introduces greater consistency and comparative relevance not currently available in the literature, and will also provide much needed pre–clinical evidence in support of treatment strategies targeting the noradrenergic system in the prevention of PTSD posttrauma. The first objective of this study was to set up and validate a passive avoidance fear conditioning protocol under our laboratory conditions using the Gemini Avoidance System. The noradrenergic system plays a prominent role in memory consolidation and fear conditioning, while administration of –adrenergic blockers, such as propranolol, have been shown to abolish learning and fear conditioning in both humans and animals. Propranolol has also demonstrated clinical value in preventing the progression of acute traumatic stress syndrome immediately posttrauma to full–blown PTSD. To confer predictive validity to our model, the centrally active –adrenergic antagonist, propranolol, and the non–centrally acting –adrenergic antagonist, nadolol, were administered to Wistar rats after passive avoidance fear conditioning training in the Gemini Avoidance System. Wistar rats were used because of their recognised enhanced sensitivity to stress. Evidence from this pilot study confirmed that propranolol 10 mg/kg significantly inhibits the consolidation of learned fear in rats, whereas nadolol is ineffective. This effectively validated our protocol and the apparatus for further application in this study and also confirmed the importance of a central mechanism of action for –adrenoceptor blockade in the possible application of these drugs in preventing the development of PTSD posttrauma. The second objective of this study was to investigate the role of 1–, 2–, 1–, and 2–receptors in a conditioned fear passive avoidance paradigm. This was done in order to investigate how selective pharmacological modulation of these receptors may modify the conditioned fear response, and whether any of these receptor systems might exert opposing effects in passive fear conditioning. Various centrally active noradrenergic agents were employed over a 3–tiered dose response design, including the 1–antagonist, prazosin, the 2–agonist, guanfacine, the 2–antagonist, yohimbine, the 1–antagonist, betaxolol and the 2–antagonist ICI 118551. The effect of post–exposure administration of these drugs on conditioned fear was compared to that of propranolol 10 mg/kg. Selected doses of betaxolol (10 mg/kg) and ICI 118551 (1 mg/kg) attenuated fear conditioning to an extent comparable to propranolol, as did prazosin (0.1 mg/kg). Yohimbine tended to boster fear learning at all doses tested, albeit not significantly, while guanfacine did not produce any significant effect on memory retention at any of the doses studied. This latter observation was surprising since yohimbine tended to bolster fear conditioning while earlier studies indicate that 2–agonism impairs conditioned fear. Concluding, this study has conferred validity to our passive avoidance model and has provided greater insight into the separate roles of noradrenergic receptors in contextual conditioned fear learning. The study has provided supportive evidence for a key role for both 1– and 2–antagonism, as well as 1–antagonism, in inhibiting fear memory consolidation and hence as viable secondary treatment options to prevent the development of PTSD posttrauma. However, further study is required to delineate the precise role of the 2–receptor in this regard. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2012.