Importance of pineal gland interactions with the sympathoadrenal system for the depressant action of reserpine

Abstract

Reserpine lowered norepinephrine and dopamine levels in the hypothalamus of rats, particularly after pinealectomy. On the other hand, its effects on catecholamine levels in the adrenals of pinealectomized rats were weaker than in intact animals. It is suggested that the depression produced by reserpine may be due in part to impaired interactions of the pineal gland with central and peripheral components of the sympathoadrenal system. Key Words: reserpine; pineal gland; sympathoadrenal system; catecholaminesOne of the central properties of reserpine is its ability to produce depression. Although the origin of this effect has traditionally been ascribed to impaired activity of reticular and limbic structures in the brain, there is evidence that its depressant action may also be due to defective operation of the sympathoadrenal system (SAS), whose strained functioning is an inevitable accompaniment of affective disorders [5,6]. One cause of these disorders may be malfunction of the pineal gland (which supplies endocrine secretions for periodic processes), in particular because of upheavals in hypothalamic-pituitary-adrenal mechanisms [1]. In view of this, we decided to examine how the pineal gland might contribute to the ability of reserpine to influence catecholamine metabolism at the central (hypothalamus) and peripheral (adrenals) levels of the SAS. MATERIALS AND METHODSThe study was conducted on random-bred male rats (body weight 100-130 g) during spring and summer months. The animals were divided into nine groups, as shown in Table 1. Physiological saline was given in repeated injections over a prolonged period, while State Medical Academy, Stavropol melatonin was injected at 0.1 mg/kg once daily for 10 days. Reserpine was injected in a dose of 2 mg/kg 24 h before the assays for catecholamines (in the melatonin-treated group, it was given after the last melatonin injection). All three substances were administered by the intraperitoneal route. Pinealectomy was performed under Nembutal anesthesia using a modified procedure developed by K. B. Ovanesov in our laboratory. The sham operation involved trephining of the skull and raising a bone flap without extirpating the pineal gland. Norepinephrine (NE) and dopamine (DA) concentrations in the hypothalamus and adrenals were measured tluo15metrically [4] after their removal from rats decapitated under ether anesthesia.All rats were kept in the vivarium under natural illumination and had free access to food and water, care being taken to standardize, as far as possible, the temperature conditions and dietary regimen in the different groups.The results were subjected to statistical treatment using Student's t test to estimate the significance of intergroup differences. RESULTSttypothalamus. Hypothalamic levels of both catecholamines in the intact rats were similar to those re-

A method for extirpation of the pineal gand in albino rats

“…On the other hand, this method does not completely preclude the effects of bioactive epiphyseal substances. Electrocoagulation of the pineal glands cannot guarantee its complete destruction [6], and hence, surgical methods should be considered more reliable, due to which they are most widely used [7,9,10]. However, it is not possible to operate many animals within a short time by the known methods of surgical removal of the pineal gland.…”