[An improved method for stereotactic location of the supraoptic nucleus with oblique stereotactic puncture in rats].

OBJECTIVE: To establish an improved method for stereotactic location of the supraoptic nucleus in rats. METHODS: Twenty-four SD rats were randomly divided into experimental group (12 rats) and control group (12 rats) for oblique (20° to the left) stereotactic puncture (OSP group) and vertical stereotactic puncture (VSP group), respectively, both targeting the supraoptic nucleus (SON). The surgical data and postoperative (within 24) mortality of the rats were compared between the two groups. RESULTS: The nucleus locating time was longer in OSP group than in VSP group (59.55∓3.64s vs 27.44∓2.18 s, P=0.000), and the postoperative mortality rate of the rats did not differ significantly between the groups (0 vs 44.4%, P=0.082). In OSP group, compared with VSP group, the procedure was associated with a lowered rupture rate of the superior sagittal sinus (11.1% vs 88.9%, P=0.003), a shortened hemostatic time after craniotomy (52.89∓24.05 s vs 157.445 ime a s, P=0.000) and after puncture (24.33 reas 45 s vs 133.89∓28.81 s, P=0.000), and also a shortened operation time (178.89 on tims vs 362.44 timees, P=0.000). CONCLUSION: The improved method for locating supraoptic nucleus in rats is convenient, stable and reproducible, and helps to avoid important blood vessels and specific nuclei according to the needs of different experiments and allows the operators to choose different surgical paths.

[Hypothalamic regulation of retinal function]. / Rol' gipotalamusa v mekhanizme regulyatsii funktsii setchatki.

UNLABELLED: Studying compensatory capacity of the brain is a pressing issue. To resolve it, diversified experiments should be conducted providing an idea of the underlying mechanisms and possibilities of functional restoration. AIM: To determine the effect of unilateral electrocoagulation of supraoptic (SO) and suprachiasmatic (SCH) hypothalamic nuclei on the appearance of the electroretinogram (ERG). MATERIAL AND METHODS: We conducted chronic experiments on awake rabbits with a total duration of 30 days. RESULTS: The study revealed considerable changes in the total ERG amplitude (reduction) as well as the amplitudes of a- and b-waves. Thus, for the first 15-30 minutes after coagulation the b-wave showed an increase, while the a-wave appeared completely suppressed. Longer postcoagulation periods were associated with gradual, though incomplete, amplitude regain of the latter. CONCLUSION: The obtained data suggest that the process of ERG recovery involves compensatory mechanisms of the SO and SCH nuclei that enable partial recovery of the neurotransmitter activity of the retina.

Investigating the role of the hypothalamic supraoptic nucleus in nociception in the rat.

We investigated the role of the hypothalamic supraoptic nucleus (SON) in nociception in the rat. Electrical stimulation of the SON or microinjection of a small dose of L-glutamate sodium into the SON elevated the nociceptive threshold in a dose-dependent manner, while cauterization of the SON decreased the nociceptive threshold. Pituitary removal did not influence the antinociceptive effect of L-glutamate sodium in the SON. The data suggested that the neurons and not the nervous fibers in the SON played an important role in antinociception.

A functional interaction between the mesolimbic dopamine system and vasopressin release in the regulation of blood pressure in conscious rats.

The aim of the present study was to further characterize the involvement of the mesolimbic dopamine system in central blood pressure regulation, with particular emphasis on the interaction of this system with the effects of circulating vasopressin. In conscious rats we stimulated the release of endogenous dopamine from mesolimbic/mesocortical terminals by administration of the substance P analogue DiMe-C7 ([pGlu5, MePhe8, Sar9]-Substance P5-11; 10 nmol) into the ventral tegmental area. Chemical stimulation of the ventral tegmental area resulted in a significant increase in blood pressure and heart rate. These effects were prevented by either bilateral electrolytic lesions of the hypothalamic supraoptic nucleus or by systemic pretreatment with the dopamine D2 receptor antagonist raclopride (0.5 mg/kg). Stimulation of the ventral tegmental area also produced a marked increase in the expression of the proto-oncogene c-fos in the supraoptic nucleus and a significant increase in plasma vasopressin levels, suggesting activation of vasopressinergic neurons in this nucleus. However, this effect of stimulation of the ventral tegmental area was not significantly inhibited by pretreatment with raclopride. We suggest that the effects on blood pressure and heart rate of stimulation of the ventral midbrain by micro-injection of DiMe-C7 are the result of combined activation of both dopaminergic and non-dopaminergic cell bodies in this region. Stimulation of non-dopaminergic cells in the ventral midbrain may induce a moderate increase in plasma vasopressin levels by activation of the supraoptic nucleus. An additional stimulation of dopaminergic cells in the ventral midbrain allows the increase in circulating vasopressin levels to become manifest as a pressor response, possibly by inhibition of vasopressin-induced facilitation of baroreflex responses.

[Role of the supraoptic nucleus in the estrus regulation in rats in local hypothermia]. / Rol' supraopticheskogo iadra gipotalamusa v reguliatsii estral'noi funktsii u krys v ulsoviiakh lokal'noi gipotermii.

An extraordinary role of hypothalamic supraoptical nuclei in the ovulation process and luteinizing hormone formation was found out. Morphological studies of the rat ovaries with the affected supraoptical nuclei have shown a sharp inhibition of their function, manifesting in the decreased follicular number of sizes, atresia of primordial follicles, the inhibition of the ovarian ovulatory capacity and luteinizing hormone formation. The ovarian function remained inhibited, despite increased neurosecretory activity of the paraventricular nucleus cells in rats with the affected hypothalamic supraoptic nuclei during hypothermia.

Changes in diurnal fluctuations of plasma thyroid stimulating hormone and corticosterone following anterior hypothalamic deafferentation in the rat.

Systemic thyroid stimulating hormone (TSH) and corticosterone (B) levels were measured in serial plasma samples withdrawn from 8 adult female rats before and for several weeks after anterior hypothalamic cuts (FC), made with a modified Halász knife (1.5 mm radius). With lights on from 5:00 to 19:00 h the rats were bled by rapid venipuncture at 9:00 and 20:00 h 14 days before and 5 days after FC and by chronic intra-atrial cannulas at 9:00, 13:00, 17:00 and 20:00 h on days 25, 30 and 40 or 50 post-FC. The frontal cuts, localized later by histology to sites just rostral to the suprachiasmatic nucleus in 3 rats and just caudal to the nucleus in the other 5 brains, altered the charactersitic diurnal drop in plasma TSH and rise in B but did not eliminate marked fluctuations in hormone levels. The new hormonal platterns could not be related specifically to FC loci and appeared to be a dynamic process for each rat. At 5 days after FC the diurnal patterns were either obscured or shifted in phase. The most consistent finding at subsequent sampling intervals was that TSH and B plasma levels in each animal showed parallel fluctuations (during 9:00--20:00 h) as though synchronized in phase. The data suggest that interruption of anterior hypothalamic connections in the female rat is compatible with fluctuations in plasma TSH and B which are unique to a particular animal and may be obscured by group analysis.

[Role of hormones of neurohypophysis in ACTH and glucocorticoid secretion]. / Rol' gormonov neirogipofiza v sekretsii AKTG i gliukokortikoidov

The absence of a strict relationship between the antidiuretic activity of the posterior lobe of the hypophysis and the ACTH-glucocorticoid secretion was shown in experiments on rats. A conclusion was drawn that the neurohypophysial hormones played no significant role in the realization of the reaction of the hypophysioadrenal system to various actions, and could influence only the spontaneous level of the ACTH-glucocorticoid secretion.