Changes in Serum Growth Hormone and Prolactin Levels, and in Hypothalamic Growth Hormone-Releasing Hormone, Thyrotropin-Releasing Hormone and Somatostatin Content, after Superior Cervical Sympathectomy in Rats

Abstract

After bilateral superior cervical ganglionectomy (SCGx) of adult male rats, norepinephrine (NE) content of the medial basal hypothalamus (MBH) decreased significantly by 39-47% from 16 h to 7 days after surgery. During this time the levels of serum growth hormone (GH) and prolactin (PRL) and of MBH GH-releasing hormone (GRH), thyrotropin-releasing hormone (TRH) and somatostatin were measured by RIA. In sham-operated controls, serum PRL increased and serum GH decreased 16–24 h after surgery, attaining pre-surgical levels later on. In SCGx rats, significantly lower serum GH and PRL and higher MBH GRH and TRH content as compared to controls was observed 16-24 h after surgery, during the wallerian degeneration phase after SCGx. MBH somatostatin concentration decreased in SCGx rats 20 h after surgery. Two injections of the α₁-adrenoceptor blocker prazosin 45 and 90 min before sacrifice, alone or together with the β-blocker propranolol, prevented the changes in MBH hypophysiotropic hormone content, as well as in serum GH and PRL levels, found in SCGx rats 20 h after surgery. Propranolol treatment did not affect hormone levels. Neither drug modified the decrease in MBH NE content observed after SCGx. The results argue in favor of the existence of physiologically relevant projections from superior cervical ganglion neurons to the MBH controlling hypophysiotropic hormone release.

Superior Cervical Ganglionectomy Effects on Median Eminence and Anterior and Mediobasal Hypothalamic Taurine Content in Male Rats: Effects of Hyperprolactinemia

“…As expected, after acute or chronic superior cervical ganglionectomy, the changes in NE content in the brain areas studied confirmed previous work from our group [9]. However, in pituitary-grafted animals the reduction was less pronounced thus indicating that, besides the surgery, prolactin modifies NE content in the brain areas studied as shown in previous work from the literature [28].…”

“…Eighteen hours or 8 days after superior cervical ganglionectomy or sham operations, the animals were killed by decapitation and the brains were immediately removed, frozen on dry ice and kept at -80°C until analyzed for TAU levels. Surgical success was confirmed by ptotic evidence and by the measurement of the NE content in the brain areas studied, as previously described [4,9].…”

“…Superior cervical ganglionectomy leads to the disappearance of the large and coarse fibers containing catecholamine associated primarily with blood vessels at the median eminence, whereas the centrally originating catecholamine terminals remain unaltered [5,6]. In ganglionectomized rats, a significant decrease in basal hypothalamic 3 H-NE uptake, together with a 40-60% decrease in Esquifino/Alvarez/Perez-Ferro/Cano/ Duvilanski this monoamine at the median eminence were observed [4,[7][8][9], thus indicating that a significant number of noradrenergic nerve terminals in the median eminence derives from the superior cervical ganglia. The median eminence NE concentration in rats fell only 60-75% after bilateral 6-hydroxydopamine lesions of the ventral pons, suggesting that, unlike the remainder of the hypothalamic nuclei, as much as 25-40% of the NE at the median eminence originates in anatomical structures outside the ventral bundle [10].…”

“…Previous studies from this group have demonstrated that changes in various pituitary hormone secretions occur during wallerian degeneration of noradrenergic terminals after acute superior cervical ganglionectomy [2,3], and the associated modifications in the hypothalamic concentrations of their hypothalamic releasing hormones [9,11] differ from those found after chronic superior cervical ganglionectomy (i.e. dopamine and serotonin turnovers decreased, whereas the secretion patterns of prolactin and growth hormone (GH) did not change [4]).…”

Acute and Chronic Effects of Superior Cervical Ganglionectomy on in vitro Mitogenic Responses of Lymphocytes from Submaxillary Lymph Nodes of Pituitary-Grafted Rats

“…These times were selected to cover both the chronic deprivation sequelae of SCGx and the transient postsynaptic activation that occurs during the early phase of anterograde ('wallerian') degeneration of SCG nerve endings in SCGx animals [13][14][15]. Such a complementary approach has enabled us to analyze the neuroendocrine consequences of an increased or decreased postsynaptic exposure to adrenergic transmitter in the thyroid [16] and parathyroid glands [17], the median eminence [18] and the posterior pituitary [19].…”