Progress in brain research
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Vasopressin (VP) and oxytocin (OT) are cyclic nonapeptides whose actions are mediated by stimulation of specific G protein-coupled receptors (GPCRs) currently classified into V1-vascular (V1R), V2-renal (V2R) and V3-pituitary (V3R) VP receptors and OT receptors (OTR). The recent cloning of the different members of the VP/OT family of receptors now allows the extensive characterization of the molecular determinants involved in ligand binding and signal transduction pathways coupled to a given VP/OT receptor subtype in stably transfected mammalian cell lines. In this article, we review the present knowledge of the signal transduction pathways coupled to the different VP/OT receptor subtypes and we present new observations derived from the study of each human VP or OT receptor subtype stably expressed in CHO cells.
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Vasopressin (VP) acts on both the locus coeruleus (LC) neurons and the neighbouring dorsal pontine reticular formation (PRF) neurons by exciting them. Experiments performed in precollicular decerebrate cats have shown that microinjection of 0.25 x 10(-11) micrograms VP into the LC complex of one side increased the extensor rigidity of the ipsilateral limbs, while rigidity of the contralateral limbs remained unmodified or slightly decreased. The amplitude of modulation and thus the response gain of both the ipsilateral and the contralateral forelimb extensor triceps brachii to sinusoidal roll tilt of the animal (at 0.15 Hz, +/- 10 degrees), leading to stimulation of labyrinth receptors, decreased significantly, while there was only a slight decrease in phase lead of the responses. ⋯ These motoneurons would then respond more efficiently to the same excitatory VS volleys elicited by given parameters of stimulation, leading to an increased gain of the EMG responses. The contralateral effects could be attributed to crossed excitation by dorsal PRF neurons of one side, either of medullary inhibitory RS neurons or of excitatory CS neurons of the opposite side, respectively. We conclude that VP controls posture and gain of the VS reflex by acting on LC neurons as well as on dorsal PRF and the related medullary inhibitory RS neurons.
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Review Comparative Study
Brain eicosanoids and LPS fever: species and age differences.
The results of the present study, summarized in Table 2, demonstrate that different species and strains of rodents (rats and mice) and birds (chickens) exhibit rather specific fever response. Systemic administration of LPS caused monophasic elevation in Tb of chickens, biphasic changes in Tb of rats (initial drop followed by an increase in Tb), whereas mice failed to develop hyperthermia and responded by a decreased Tb. The LPS-induced alterations in hypothalamic prostanoid synthesis were also rather species-specific and differ markedly even between the two strains of mice. ⋯ The reduced febrile response is considered, at least in part, to contribute to an increased mortality and prolonged recovery from infections (Kluger, 1986). From this point, it is difficult to suggest whether the hypothermia observed in our mice and rats could be of somewhat adaptive significance. It has been shown that at the ambient temperature of 30 degrees C, Swiss Webster mice can re