Further studies on the role of cholecystokinin-A and B receptors in secretion of anterior pituitary hormones in male rats

We compared the effects of unselective cholecystokinin (CCK) agonists (caerulein and CCK-8s) and a CCKB agonist CCK-4 on the secretion of thyrotropin (TSH), growth hormone (GH) and prolactin (PRL) in male rats. The subcutaneous (s.c.) administration of caerulein and CCK-8s suppressed dose-dependently TSH and GH levels. In contrast, when given into the 3rd brain ventricle (i.c.v.) caerulein dose-dependently elevated the GH levels. Next the importance of the afferent vagal nerves was studied in the action of caerulein and CCK-4. Subdiaphragmatic vagotomy itself decreased cold-stimulated TSH levels but abolished the suppressing effect of intraperitoneal (i.p.), and apparently also that of the i.c.v. caerulein. GH and PRL levels were altered neither by vagotomy nor caerulein. CCK-4 did not affect hormone levels. Atropine and butylscopolamine (i.p.) themselves did not alter TSH, PRL or GH secretion in intact rats. Neither did they reverse the effect of caerulein on TSH. In conclusion, CCKA receptors dominate in TSH and CCKB receptors in GH regulation. CCKA receptors in the gastrointestinal tract, related to the nervus vagus are mediating the inhibitory effect of caerulein upon TSH secretion but inhibition of GH secretion does not depend on the nervus vagus. CCKB receptors in the brain stem or near the 3rd brain ventricle are responsible for stimulation of GH secretion

Acute effects on perch (Perca fluviatilis) and long-term effects on whitefish (Coregonus lavaretus pallasi) of liming of an acidified lake

The acute effects on perch and long-term effects on whitefish were studied after liming one side of a lake [initial pH: 4.6–5.5; aluminium (Al): 29–54 lg L)1; Ca2+: 0.02–0.07 mmol L)1] that was divided into two parts with a plastic curtain. Some Al precipitation was observed on the gill surface of perch 1 day after liming; the concentration of plasma sodium of perch females in the limed side was also higher than in the acidic side. Nearly 6 months after liming, at the spawning time of whitefish, the plasma chloride concentration of whitefish in the limed side was higher and blood glucose concentration lower than in the acidic side. Four of five whitefish males from the limed side, but only one of five males and none of the five females from the acidic side, were ready to spawn. The growth of whitefish in the limed side was also more rapid. These changes illustrate that liming had no acute harmful effects on perch, and allowed whitefish to recover from acidity-related physiological stress