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Morphine withdrawal is characterized by functional alterations at the level of the ventrotegmental area. We investigated the effects of chronic morphine administration and withdrawal on the morphological properties of immuno-labelled tyrosine hydroxylase-positive neurons of the rat ventrotegmental area with a confocal laser scanning microscope. Morphological evaluation revealed a reduction in the area and perimeter of tyrosine hydroxylase-positive somata in morphine-withdrawn rats. Conversely, the number of cells per field was found to have increased in the naloxone group. Collectively, the present results indicate that withdrawal from a chronic morphine treatment, and not chronic morphine per se, modifies cellular morphology of tyrosine hydroxylase-positive, presumably dopamine-containing, neurons of the rat VTA. This is consistent with the idea that withdrawal from morphine alters functioning of the mesolimbic dopamine system and provides a direct morphological correlate for the functional abnormalities typical of morphine withdrawal.

Apart from raclopride and olanzapine, the APs with lower extrapyramidal effects could be distinguished from typical APs on the basis of their ability to preferentially stimulate DA transmission in the NAc shell. There was no relationship between stimulation of PFCX DA and atypical APs profile. The differences between this study and voltammetry studies were not attributable to pargyline pretreatment.

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Caffeine enhances the reinforcing effects of cocaine and its motivational value. Our results highlight the role of active adulterants commonly used in cocaine-based illicit street drugs.

The distribution of somatostatin-like immunoreactivity in the brain of the cave salamander Hydromantes genei (Amphibia, Plethodontidae) was investigated by using two distinct antisera raised against somatostatin-14. Most somatostatin-positive cells were detected in the ependymal cell layer surrounding the ventricles. These cells possessed the typical morphological characteristics of tanycytes or radial glial cells. Double-labeling with an antiserum against somatostatin and a monoclonal antibody against glial fibrillary acidic protein showed that somatostatin-immunoreactive cells lining the ventricles also exhibited GFAP-like immunoreactivity. Injection of the neurotracer biocytin into the lateral ventricle revealed that neurons lining the ventricles did not contain somatostatin-like immunoreactivity. In the telencephalon, somatostatin-like immunoreactivity was confined to radial glial cells. In the diencephalon, in addition to somatostatin-immunoreactive cells in the ependyma, positive cell bodies were also found in the periventricular preoptic nucleus, the infundibular nucleus, the epiphysis, and the subcommissural organ. In the metencephalon, positive cell bodies were found in the auricula cerebelli, whereas in the rhombencephalon numerous somatostatin-immunoreactive cells were seen lining the ventricular cavity. Immunoreactive nerve fibers were observed in the hypothalamus-median eminence complex. In the pituitary, a discrete group of somatostatin-positive cells was found in the pars distalis. High-performance liquid chromatography analysis of brain extracts revealed that the immunoreactive material coeluted with somatostatin-14. The present results show that the somatostatin peptidergic system in the brain of the cave salamander has a more simple organization than those described in the brain of frog and other vertebrates. This feature is probably related to the expression of high pedomorphic characters in plethodontids. The distribution of somatostatin-like immunoreactivity suggests that, in the cave salamander, somatostatin may act as a neurotransmitter and/or neuromodulator, a central regulator of fluid homeostasis, and a hypophysiotropic neurohormone.

The mental glands of Hydromantes genei are considered a specialized form of the urodele serous cutaneous glands. Use of a variety of techniques of maceration and digestion as well as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) has shown the three-dimensional morphology of secretory and myoepithelial cells. Secretory cells are pyramidal and rest on an almost continuous layer of myoepithelial cells. The latter have a long ribbon-like body from which branch off transversal and longitudinal processes with swallow-tailed ends. Cytoplasmic processes of secretory cells, containing irregular dense vesicles, squeeze through clefts between myoepithelial cells and may reach, at some points, the basal lamina. The interstices between myoepithelium and secretory cells are extraordinarily rich in nerve endings with clear vesicles. The glandular outlets appear as elliptical stomata in the superficial layer of the epidermis and are lined by horny cells, which invaginate to circumscribe the excretory duct. The morphological results indicate that the myoepithelium of Plethodontidae mental glands differ in some respects from that of amphibian serous cutaneous glands. A double polarity for the secretory cells is also suggested. © 1993 Wiley-Liss, Inc.

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