Persistent hypotensive effect of L-dopa given early during development to rats with inherited stress-induced arterial hypertension

Animal Models of Hypertension (ISIAH Rats), Catatonia (GC Rats), and Audiogenic Epilepsy (PM Rats) Developed by Breeding

Research into genetic and physiological mechanisms of widespread disorders such as arterial hypertension as well as neuropsychiatric and other human diseases is urgently needed in academic and practical medicine and in the field of biology. Nevertheless, such studies have many limitations and pose difficulties that can be overcome by using animal models. To date, for the purposes of creating animal models of human pathologies, several approaches have been used: pharmacological/chemical intervention; surgical procedures; genetic technologies for creating transgenic animals, knockouts, or knockdowns; and breeding. Although some of these approaches are good for certain research aims, they have many drawbacks, the greatest being a strong perturbation (in a biological system) that, along with the expected effect, exerts side effects in the study. Therefore, for investigating the pathogenesis of a disease, models obtained using genetic selection for a target trait are of high value as this approach allows for the creation of a model with a "natural" manifestation of the pathology. In this review, three rat models are described: ISIAH rats (arterial hypertension), GC rats (catatonia), and PM rats (audiogenic epilepsy), which are developed by breeding in the Laboratory of Evolutionary Genetics at the Institute of Cytology and Genetics (the Siberian Branch of the Russian Academy of Sciences).

Chronic stress during prepubertal development: immediate and long-lasting effects on arterial blood pressure and anxiety-related behavior

The present work was undertaken to study the immediate and long-lasting effects of environmental stress during prepubertal life in rats with inherited stress-induced arterial hypertension (ISIAH) and normotensive Wistar rats on blood pressure (BP) levels and anxiety-related behavior. Two models of chronic stress (21-32 postnatal days) were used: repeated handling (HS) and unpredictable stress (US) of daily exposures to a variety of mild physical or psychoemotional stressors. Rats were tested just after the end of the chronic stress period and then at the age of 4 months. Chronic prepubertal stress did not affect the basal or stress-induced BP levels in young or adult Wistar rats. In ISIAH rats, chronic stress during the early phase of hypertension development did not accelerate its formation and did not augment its manifestation in adults. Moreover, the basal BP was decreased in young and adult ISIAH rats exposed to HS or US as compared to the age-matched controls. No long-lasting effect on BP elevation under acute stress in adults was found. Plasma corticosterone levels at resting and acute stress conditions were not changed in adult rats that had experienced prepubertal stress. Hypertensive rats proved to be less anxious in the elevated plus-maze test. The immediate effects of chronic stress were similar in the two rat strains: HS had an anxiolytic action while US stimulated anxiety. Long-lasting consequences depended on the rat strain: the anxiolytic effect of HS was retained in Wistar rats and US caused a greater anxiety in adult ISIAH rats. The data do not evidence that symptoms of anxiety are related to the development and maintenance of stress-sensitive arterial hypertension in ISIAH rats.

Immediate and long-lasting effects of chronic stress in the prepubertal age on the startle reflex

The immediate and long-lasting effects of two models of chronic stress during the prepubertal period of life (21-32 days) on the acoustic startle response (ASR) were studied in outbred Wistar normotensives and rats with inherited stress-induced arterial hypertension (ISIAH) derived from them. Chronic variable stress (CVS) and repeated handling were used as chronic treatment. The obtained data showed a significantly attenuated ASR and a greater magnitude of prepulse inhibition (PPI) in juvenile and adult ISIAH compared to Wistar rats. The immediate effects of prolonged stress on the ASR were genotype-dependent. Young ISIAH rats exposed to both types of prepubertal stimulation had higher ASR than the age-matched controls. No significant stress-induced changes in the ASR were found in young Wistar rats. The long-lasting consequences of prolonged prepubertal stress were similar in the two strains and were determined by the specificity of stress stimulation: chronic handling had no effect on the ASR, while CVS enhanced it. The long-lasting effect of CVS experienced in prepubertal life appears to produce ASR changes similar to those seen in patients with posttraumatic stress disorder (PTSD). The magnitude of PPI increased from early age to adulthood and it was tolerant to environmental influences. The two rat strains did not differ in the rate of short-term habituation to repeated acoustic stimuli, which was unaffected by prepubertal stress. Evidence was obtained indicating that genetic and environmental background in childhood may contribute to the truncation of the startle response.

Treatment with L-dopa in early life restored pituitary-adrenocortical response to emotional stress in adult rats with inherited arterial hypertension

This study investigates the function of the hypothalamic-pituitary-adrenocortical system (HPAS) in adult rats with inherited stress-induced arterial hypertension (ISIAH rats) whose arterial blood pressure was lowered by the dopamine precursor L-DOPA treatment during early development (on days 21-25 of life). The response of the HPAS induced by emotional stress was significantly lower in intact ISIAH rats than in normotensive Wistar animals. Injections of L-DOPA on days 21-23 or 21-25 of postnatal life were followed by a long-lasting complete restoration of the emotional stress response in adult ISIAH rats. The restoring effect of L-DOPA was produced through enhancement of synthesis of the brain noradrenaline and, perhaps, adrenaline. The effect was associated with a normalization of the response of the brain adrenergic system to noradrenaline and did not relate to an increase of the plasma corticosterone level after L-DOPA administration in early ontogeny.