Oxytocin (OXY) has been shown to attenuate some of the physiological and behavioral alterations appearing in stressed rats. Carbetocin (CBT), an oxytocin analog [deamino-1-monocarba-(2-O-methyltyrosine)-oxytocin], was designed to exert prolonged action. In the present study we investigated the impact of these peptides on the behavioral changes in rats exposed repeatedly to restraint stressors. Wistar male rats were exposed to restraint for 1 hour; saline or drugs were administered intraperitoneally immediately after stress termination. Recording of the exploratory activity in the open-field started 60 min later. To explore the possibility of persisting effects of stress and/or drugs, the procedure was repeated for three consecutive days. Restraint moderately suppressed locomotion and rearing, and increased grooming. OXY in 0.3 mg/kg dose showed a tendency to restore the suppressed exploratory activity. In contrast, 1 mg/kg dose potentiated the stress-induced behavioral deficit. Both OXY doses slightly increased grooming. CBT in the same two doses restored the stress-induced deficits in locomotion and rearing but did not influence grooming. The locomotor depression after 1 mg dose of OXY was found also in non-stressed rats in contrast to the increased activity after CBT. The data support the view that post-stress administered CBT exerts a significant effect on the stress-altered spontaneous behavior.
Post-feeding diuresis in Rhodnius prolixus is neurohormonally controlled by serotonin and at least one peptidergic diuretic hormone (possibly a CRF-related peptide). These appear to be released by two different neurosecretory groups – 5 dorsal unpaired median (DUM) cells and 5-6 lateral neurosecretory cells of the mesothoracic ganglionic mass. The DUM cells co-localize serotonin and the calcitonin-related peptide RhoprDH31. The lateral neurosecretory cells co-localize a CRF-related peptide and a kinin-like peptide. Serotonin and the CRF-related peptide, ZooneDH, each stimulate maximum secretion by the upper Malpighian tubules, whereas only serotonin stimulates KCl reabsorption from the lower Malpighian tubules. RhoprDH31 is only weakly diuretic and Leucokinin 1 has no diuretic activity. Neither stimulates KCl reabsorption. The possible role for multiple diuretic hormones and for co-localization of diuretic factors is discussed.
Neuropeptides are ubiquitous intercellular signalling molecules in all Metazoa with nervous systems. Research over the past 10 years has confirmed through immunocytochemistry that neuropeptides are widespread and abundant in the nervous systems of helminth parasites. Biochemical isolation and characterisation studies have indentified the primary structures of numerous structurally- related peptides in helminths, the best studied being the FMRFamide-related peptides (FaRPs). While to date only four FaRPs have been identified from platyhelminths, some 60 FaRPs or FaRP-like peptides have been isolated or predicted for nematodes. Preliminary physiological studies have shown that FaRPs are strongly myoactive, but with quite different actions in the two groups of helminth parasite. The absence of FaRPs from vertebrates suggests compounds with a high affinity for FaRP receptors are likely to have selective effects against helminths and, if protected from degradation, could have therapeutic potential.
In Lytocestus indicus putative neurosecretory cells (pNSC) are recognized on the basis of phloxinophilic and fuchsinophilic nature of their cytoplasm; pNSC in L. indicus are dimensionally small. Morphologically, there are four types of pNSC: a-, uni-, bi-, and multipolar cells. They are found both in the cortical and medullary parenchyma of the neck and strobilar regions; in the latter the pNSC occur in close vicinity with the longitudinal muscles and components of the reproductive system.
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