The Expression Patterns of c-Fos and c-Jun Induced by Different Frequencies of Electroacupuncture in the Brain

To investigate patterns of c-Fos and c-Jun expression induced by different frequencies of electroacupuncture (EA) in the brain, goats were stimulated by EA of 0, 2, 60, or 100 Hz at a set of "Baihui, Santai, Ergen, and Sanyangluo" points for 30 min. The pain threshold was measured using the potassium iontophoresis method. The levels of c-Fos and c-Jun were determined with Streptavidin-Biotin Complex immunohistochemistry. The results showed that the pain threshold induced by 60 Hz was 82.2% higher (P < 0.01) than that by 0, 2, or 100 Hz (6.5%, 35.2%, or 40.9%). EA induced increased c-Fos and c-Jun expression in most analgesia-related nuclei and areas in the brain. Sixty Hz EA increased more c-Fos or c-Jun expression than 2 Hz or 100 Hz EA in all the measured nuclei and areas except for the nucleus accumbens, the area septalis lateralis, the caudate nucleus, the nucleus amygdala basalis, and the locus coeruleus, in which c-Fos or c-Jun expressions induced by 60 Hz EA did not differ from those by 2 Hz or 100 Hz EA. It was suggested that 60 Hz EA activated more extensive neural circuits in goats, which may contribute to optimal analgesic effects.

Neural connectivity in the mediobasal hypothalamus of the sheep brain

The ventromedial nucleus of the hypothalamus (VMN) and the arcuate nucleus (ARC) are two centres regulating energy balance and food intake, but inter-connectivity of these nuclei is not well defined in non-rodent species. In this study, we performed retrograde tracing and immunohistochemistry in the ovine brain with ewes receiving FluoroGold (FG) injections into either ARC or VMN for the mapping of retrogradely labelled cells. Strong reciprocal connections were found between the two regions. The distribution of the FG labelled neurons in other regions of the hypothalamus and brain stem was also mapped. Some of the cells projecting from ARC to VMN were immunopositive for neuropeptide Y, galanin, adrenocorticotropin (marker of pro-opiomelanocortin cells) or tyrosine hydroxylase (marker of dopaminergic cells). Melanin-concentrating hormone and orexin neurons in the lateral hypothalamic area were also found to provide input to the VMN and ARC. This observed interconnectivity between regions important for metabolic regulation and other neuroendocrine functions presumably allows coordinated functions. Input to both the ARC and VMN from other brain regions, such as brain stem cell groups, provides a further level of regulation. These data provide a substrate upon which further understanding of appetite regulation and neuroendocrine function can be derived in this species.

alpha-Melanocyte-stimulating hormone and oxytocin: a peptide signalling cascade in the hypothalamus

alpha-Melanocyte-stimulating hormone (alpha-MSH) and oxytocin share remarkable similarities of effects on behaviour in rats; in particular, they both inhibit feeding behaviour and stimulate sexual behaviour. Recently, we showed that alpha-MSH interacts with the magnocellular oxytocin system in the supraoptic nucleus; alpha-MSH induces the release of oxytocin from the dendrites of magnocellular neurones but it inhibits the secretion of oxytocin from their nerve terminals in the posterior pituitary. This effect of alpha-MSH on supraoptic nucleus oxytocin neurones is remarkable for two reasons. First, it illustrates the capacity of magnocellular neurones to differentially regulate peptide release from dendrites and axons and, second, it emphasises the putative role of magnocellular neurones as a major source of central oxytocin release, and as a likely substrate of some oxytocin-mediated behaviours. The ability of peptides to differentially control secretion from different compartments of their targets indicates one way by which peptide signals might have a particularly significant effect on neuronal circuitry. This suggests a possible explanation for the striking way in which some peptides can influence specific, complex behaviours.