Vasopressin in the brain of a desert hibernator, the jerboa (Jaculus orientalis): presence of sexual dimorphism and seasonal variation.

The distribution of vasopressin innervation in the brain of the jerboa (Jaculus orientalis) was investigated, with special attention to sex differences and seasonal variations. Vasopressin perikarya were observed in the paraventricular and supraoptic nuclei, the suprachiasmatic nucleus, the periventricular nucleus, the medial preoptic area, the bed nucleus of the stria terminalis, and the medial amygdaloid nucleus. In addition, vasopressin cell bodies were observed in the ventral retrochiasmatic area. After treatment with colchicine, vasopressin perikarya were also observed around the organum vasculosum laminae terminalis, in the medial diagonal band of Broca, and in the dorsal medial preoptic nucleus. Vasopressin fibers were also found to be more widespread in the jerboa brain than in other rodents. Fibers were observed in the medial diagonal band of Broca, the stria medullaris, the tuber cinerum, the area postrema, the medial vestibular nucleus, and the dorsal motor nucleus of the vagus. Sexual dimorphism and seasonal variation in vasopressin immunoreactivity were observed in areas that not only showed a testosterone-dependent vasopressin innervation in other rodents but also in the paratenial and mediodorsal thalamic nuclei, the tuber cinerum, the supramammillary complex, the zona incerta, the interpeduncular complex, and the dorsal and medial raphe nuclei. A denser vasopressin innervation was observed in spring/summer (sexual active period) than in autumn. Numerous brain structures contained vasopressin receptors (cerebral cortex, hypothalamus, substantia nigra, dentate gyrus, thalamic nuclei, superior colliculus, dorsal cochlear nucleus, and cerebellum); no sex- or season-related differences were observed. These data indicate a high level of vasopressin in the jerboa brain, which may reflect an adaptation to its harsh bioclimatic environment.

Alpha-adrenoceptors and monoamine contents in the cerebral cortex of the rodent Jaculus orientalis: effects of acute cold exposure.

The tritiated adrenergic antagonists prazosin ([3H]PRZ) and idazoxan ([3H]IDA, or RX-781094) bind specifically and with high affinity to alpha 1- and alpha 2-adrenoceptors respectively, and were used to measure adrenoceptors in membrane preparations obtained from the cerebral cortex of Jaculus orientalis. Membrane preparations were also obtained from a group of cold exposed animals, to determine whether these adrenoceptors could be modified by a thermic stress. The density of receptors (Bmax; maximum binding capacity) and the dissociation constant (Kd 25 degrees C) were estimated by iterative modelling, and by using the procedure of Hill. After acute cold exposure (16 hr, 5 degrees C) there was a decrease in the affinity of the alpha 1-adrenoceptors, as judged by the Kd 25 degrees C for [3H]PRZ, with no changes in the Bmax. The alpha 2-sites did not show any significant changes, as revealed by [3H]IDA binding. Pretreatment of the membrane preparations from control animals with the disulfide and sulfhydryl reactives DL-dithiothreitol, 5,5'-dithiobis-(2-nitrobenzoic acid) and N-ethylmaleimide decreased specific [3H]PRZ and [3H]IDA binding, with minor changes in non-specific counts, indicating that the fixation of these ligands was to the receptor proteins. The endogenous cortical monoamine contents were also determined in the frontal cerebral cortex of these same animals, using high performance liquid chromatography with electrochemical detection. The catecholamine levels and their major metabolites were found to be stable in the cortex after the acute thermic stress, but there was a marked reduction in serotonin with a normal content in 5-hydroxyindole-3-acetic acid.

Behavioral consequences of dietary vitamin deficiency in young and middle-aged rats.

The behavioral correlates of vitamin A and B 6 dietary deficiency in young adult rats (Experiment 1) and middle-aged, retired breeder rats (Experiment 2) were examined. Male and female rats received either vitamin A deficient, vitamin B6 deficient, or normal control diets for two and a half months. Body weight, eating, and drinking of water and adulterated fluids were monitored. Pyridoxine deficiency generally had greater effects on consummatory behavior and weight gain than vitamin A deficiency, but this effect was influenced by the rats' age and sex. Wheel running, (Experiment 1), increased above control levels in both the vitamin delete groups. Vitamin A and B 6 deplete diets may affect behavior before an animal displays classical physical signs. Furthermore, such behavioral changes are not restricted to young, rapidly growing male rats; instead, their character is influenced by both the sex and age of the animal.