Effects of chronic tryptophan loading on serotonin (5-HT) levels in neonatal rat brain.

Several earlier studies reported that the acute administration of L-tryptophan to adult rats caused an increase in brain serotonin levels. This study describes the effects of chronic tryptophan loading on serotonin concentration levels in various regions of the neonatal rat brain. Rats were injected with tryptophan methyl ester hydrochloride (100 mg/kg), intraperitoneally, daily from day 4 to day 24 after birth, and sacrificed on days 8, 19, and 29 after first injection. The brains were immediately dissected into their component regions, and serotonin concentration levels were measured by a radioenzymatic method. Chronic tryptophan loading produced a significant (P < .05) decrease in serotonin levels in all the brain regions as compared with saline-treated controls, except the pons and medulla regions, which showed significant (P < .001) increase on day 8.

Methadone blocks dopamine-mediated release of gonadotropins in rat hypothalamus.

In the present study the effect of methadone (M) on gonadotropin-releasing hormone in the rat hypothalamus was investigated. The specificity of the M effect was demonstrated by injecting M (100 ng) and the M antagonist, naloxone (5 ng), into the ventromedial hypothalamus. A significant drop in the blood testosterone level (p less than 0.05) 15 min following M injection and reversal following naloxone administration suggest a decrease in synthesis or release of LHRH. To determine whether the LHRH response to dopamine (DA) is altered by M, studies were conducted in vitro and in vivo. For the in vitro study hypothalami were incubated with M (10(-7) M), DA (10(-7) M), DA plus M, and DA plus M plus naloxone. Supernatants from the incubate were used to coincubate pituitaries in order to study the effect on luteinizing hormone release. Treatment of the hypothalamus with M had no effect on basal but inhibited the DA-stimulated release of LHRH. For the in vivo study rats were pretreated with decarboxylase inhibitor (RO4-4602) followed by treatment per kilogram body weight with M (10 mg), L-dopa (1, 10, and 100 mg), L-dopa plus M, LHRH (500 ng), and M plus LHRH. M had no effect on the LHRH-induced increase in testosterone levels, whereas the L-dopa-induced increase in testosterone was blunted by M treatment. It is concluded that M blocks the DA-mediated release of gonadotropin-releasing hormone in the rat hypothalamus.

Neuroendocrine organs of the lemon-butterfly, Papilio demoleus L. III. Metamorphic changes in the retocerebral endocrine organs.

The retrocerebral endocrine organs, the corpora cardiaca and corpora allata were studied in different developmental stages of the lemon-butterfly. The organs were found to undergo several changes in respect of their position, size, structure and the number of nerves associated with them.

Neuroendocrine organs of the lemon-butterfly, Papilio demoleus L. II. The corpora cardiaca-allata complex of the adult.

The retrocerebral endocrine organs of the adult lemon-butterfly; Papilio demoleus have been described. The organs are subaortic lying closely behind the brain. While the nervi corporis cardiaci I (NCCI) originate from the protocerebrum of the brain, the NCCII seem to take their origin in the tritocerebrum in common with another nerve named earlier as the tegumentary nerve. The corpora cardiaca (CC) and corpora allata (CA) are closely approximated to each other obliterating the nervi corporis allati (NCA) which are conspicuous in the larva of the same species. An intercardiacal bridge (ICB) connects the CC of the two sides and acts as a possible centre of distribution for the neurosecretory material (NSM) to the gut. Histological evidence suggests that the NSM inside the CC remains intraaxonal without being primarily unloaded in the organs for storage. The intrinsic secretory cell of the CC are intimately associated with the neurosecretory fibres from the brain and bear fairly thick axons. No NSM could be detected in the CA of this insect.

Neuroendocrine organs of the lemon-butterfly, Papilio demoleus L. I. The corpora cardiaca-allata complex of the larva.

The histomorphology of the retrocerebral endocrine organs of the larva of the lemon-butterfly, P. demoleus has been described employing a conventional neurosecretory staining technique. The larval organs lie a little away from the brain and oesophagus and, therefore, are not sub-aortic in position unlike most other insects and the adult of this species itself. There are two long NCCs which innervate other target organs in addition to the CC. The recurrent nerve of the stomatogastric nervous system retains its normal connections with the CC even in absence of the hypocerebral ganglion. Histological evidence suggests that the NSM inside the CC remains intraaxonal without being possibly unloaded in the substance of these organs. Axonal transport of NSM to target organs is also in evidence and though NSM is seen in the NCA, it could not be detected inside the CA.

Histological study on the retrocerebral endocrine-aortal complex of the water-bug, Sphaerodema annulatum (Heteroptera: belostomatidae) with reference to secretory inclusions.

Unlike many heteropterans, the retrocerebral endocrine organs of the water-bug, Sphaerodema annulatum are not fused with each other or with the hypocerebral ganglion. The NCC I bypass the CC and also innervate the oesophageal dilator muscles, CA and post-allatal pericardial cells in addition to aorta. Terminall, this nerve dilates into an ampulla showing accumulation of NSM and, therefore, regarded as a transitory storage centre. Each CC is divisible into two histological halves; the anterior half being negative and the posterior half positive to AF. The CA are innervated by two NCAs one of which (the NCA I) ramifies to form a NSM containing nerve-net on the surface of the gland regarded as another transitory storage centre. Three qualitatively different secretory factors are recognised in the retrocerebral endocrine-aortal complex of this insect -- of which one, localised in the posterior half of the CC, is regarded as indigenous and the other two present in the CA, aorta and pericardial cell nerves as cerebral in origin. Of the latter, both the factors are transported to the CA while only one to the aorta and pericardial cell nerves.