Neuropeptide Y localization in telencephalic and diencephalic structures of the ground squirrel brain.

The distribution of neuropeptide Y-immunoreactive (NPY-IR) perikarya, fibers, and terminals was investigated in the brain of two species of hibernatory ground squirrels, Spermophilus tridecemlineatus and S. richardsonii, by means of immunohistochemistry. In the telencephalic and diencephalic structures studied, distinct patterns of NPY-IR were observed which were essentially identical in male and female animals of both species.

Immunohistochemical evidence for the presence of neuropeptides in the hypothalamic suprachiasmatic nucleus of ground squirrels.

The cytoarchitecture and immunocytochemical distribution of neuropeptides (corticotropin-releasing factor, CRF; neuropeptide Y, NPY; oxytocin, OXY; vasopressin, VP; and vasoactive intestinal polypeptide, VIP) were studied in the hypothalamic suprachiasmatic nuclei (SCN) in male and female ground squirrels of two species (Spermophilus tridecemlineatus and S. richardsonii). Immunoreactive (IR) perikarya were found in sections incubated with VP or VIP antisera.

Comparative studies on the retinal dopamine response to altered magnetic fields in rodents.

Previously it was demonstrated that experimental alteration of the ambient magnetic field at night significantly reduced catecholamine levels in the retinae of Sprague-Dawley rats. As this effect appeared to depend on intact photoreceptors, it seemed of interest to examine whether the dopamine response to altered magnetic fields (MFs) differed between rod-dominant retinae and cone-dominant retinae. Furthermore, the effect of MFs on daytime dopamine content was explored.

Pineal sensitivity to nighttime swimming stress changes during the active season in Richardson's ground squirrels (Spermophilus richardsonii).

Melatonin synthesis in the pineal gland, which is primarily regulated by the environmental lighting regime, can also be influenced by other factors that elicit modifications in sympathetic tone. The objectives of this study were to determine if forced swimming alters the normal pattern of melatonin production in the pineal gland of the Richardson's ground squirrel (Spermophilus richardsonii). In early June, the squirrels were forced to swim for 10 min during the photophase or during the scotophase.

Thyroxine 5'-deiodination in brown adipose tissue and pineal gland: implications for thermogenic regulation and role of melatonin.

T4 type II 5'-deiodinase (5'-D II) activity was studied in wild-captured Richardson's ground squirrels. As previously reported for other species, 5'-D II activity was detected in frontal cortex, cerebellum, pineal gland, and brown adipose tissue (BAT); in the median eminence the levels of 5'-D II activity were undetectable with our methodology. When pineal gland, frontal cortex, and cerebellum nyctohemeral profiles were studied, none of them showed variations.