The vasopressinergic innervation of the brain in normal and castrated rats

The distribution of hypothalamic and extrahypothalamic vasotocinergic cells and fibers in the brain of a lizard, Gekko gecko: presence of a sex difference

The distribution of vasotocin in the brain of the lizard Gekko gecko was studied with immunocytochemical methods. Vasotocinergic cells were found in the nucleus supraopticus, the nucleus paraventricularis, the bed nucleus of the stria terminalis, and in the rhombencephalon. Vasotocinergic fibers were found in the preoptic area, the lateral and ventral hypothalamus, and in many extrahypothalamic brain areas. Furthermore, evidence was obtained of a conspicuous sex difference with regard to vasotocinergic innervation of the lateral septum, the ventrocaudal telencephalon (nucleus sphericus), and the periaqueductal gray; in these areas vastocinergic innervation is much denser in males than in females. The results are discussed in relation to the sexually dimorphic vasopressinergic innervation of the rat brain. It is suggested that the vasotocinergic fiber system in the sexually dimorphic brain areas in Gekko gecko is related to the bed nucleus of the stria terminalis.

Coexistence of vasopressin, neurophysin and noradrenaline immunoreactivity in medium-sized cells of the locus coeruleus and subcoeruleus in the rat

Vasopressin-and neurophysin-immunoreactive cells have recently been demonstrated in the rat locus coeruleus (A6) and subcoeruleus (A7). Using consecutive 5 microns thick frozen sections, medium-sized cells throughout the locus coeruleus area, but predominantly in the posterior parts of the A6 displayed coexistence for vasopressin and noradrenaline or neurophysin and noradrenaline immunoreactivity. The putative projection areas of putative fibers from vasopressin-containing cells in the locus coeruleus still remain to be elucidated.

A daily rhythm in behavioral vasopressin sensitivity and brain vasopressin concentrations

The concentration of Arg-vasopressin (AVP) in the suprachiasmatic nuclei of the hypothalamus (SCN), the neural generator of circadian rhythms, showed a daily rhythm, which was inversely related to the rhythm in lordosis, an aspect of sexual behavior shown by ovariectomized estradiol-17 beta-treated female rats. A threshold dose of an AVP antagonist facilitated sexual behavior most effectively if injected intracerebroventricularly when the endogenous levels of AVP in the SCN were maximal and a threshold dose of AVP inhibited the behavior most effectively if injected when these levels were minimal. The results support the suggestion that AVP may be the neuropeptide whereby the SCN generate some behavioral rhythms.

Neuropeptide effects on brain development to be expected from behavioral teratology

A wealth of literature has become available about lasting functional consequences of perinatal psychotropic drug exposure, having affected brain development in a subtle rather than gross structural way (behavioral teratology or functional neuroteratology). The underlying mechanism is thought to result from changing levels of neurotransmitters during neurogenesis induced by these neuroactive drugs, which as a consequence appears to lead to impaired cell acquisition and receptor setting i.e., to irreversible changes in particular neuronal circuitries. Neuropeptides are true candidates for a neurotransmission function as well, and are also present early in brain development. As for the classical neurotransmitters, a role for neuropeptides in the growth and functional organization of the nervous system, might therefore be expected. Anomalies in neuropeptide levels also would lead to functional neuroteratology. Although not overwhelming, several studies support this view, and the current state is summarized in this paper: a trophic role for some neuropeptides as well as neuroteratological effects upon perinatal manipulation for others were revealed. However, more detailed studies are necessary, certainly also because of the crying need for exposing possible adverse effects at a time when clinical applications of neuropeptides and their analogues are becoming a mode.