Neuronal Uptake of Monoclonal Anti‐Vasopressin Antibodies in vivo and Relationship with the Physiological Status of Vasopressin Neurosecretory Cells

Abstract

Key words: vaso p less I n , i rn rn u n oc y t oc he m is t ry , n e u ro n a I uptake , in vivo, rno rp h o me t r ic analysis. AbstractMouse monoclonal anti-vasopressin antibody was injected just above one hypothalamic paraventricular nucleus of the rat brain. lmmunocytochemistry and morphometric analysis showed that the antibody was taken up by neurons with the size and stereotaxic distribution of vasopressin-producing neurons. Labelled neurons were counted with an electronic image analyser. When the rats were deprived of drinking water for 48 h before injection, specific uptake was significantly increased in the caudal part of the nucleus. Conversely, rehydration following dehydration or chronic treatment with 1-deamino-8-D-arginine vasopressin significantly decreased neuronal uptake, mainly in the rostra1 subdivision of the nucleus. By contrast, bilateral adrenalectomy performed 2 weeks before injection did not modify the number of labelled magnocellular neurons, though the accumulation of injected antibody in the external layer of t h e median eminence indirectly demonstrated the stimulation of antibody uptake by parvocellular vasopressin neurons.The number of labelled neurons w a s therefore directly related to the physiological state of the vasopressin-producing neurons. Further investigations will have to be performed to prove that the immunological targeting of peptidergic neurons offers a new tool to act in vivo on central neurons.It has recently been demonstrated in our laboratory that monoclonal antibodies (MAbs) raised against a neuropeptide, vasopressin (VP), penetrated into neurons when they were injected into the brain (I). This uptake was specific and occurred in vivo in VPproducing neurons. Labelled neurons were revealed in the brain of rats sacrificed 5 min to 3 h after the injection. VP-MAbs were then transported to neuron terminals, and this transport was inhibited by the prior injection of colchicine. Despite the high concentration of injected specific immunoglobulins and a diffusion volume including all VP neurons of the injected area most, though not all of the VP neurons, were labelled in vivo. This finding suggested that uptake of VP-MAb was modulated and it prompted the question whether neuronal activity might be responsible for this modulation. The present study was designed to obtain further information about the number of VP-producing neurons which take up VP-MAbs in the normal rat. In addition, quantitative analysis of labelled neurons was performed in rats deprived of drinking water ('dehydrated' rats), in rats given water after a period of deprivation ('rehydrated' rats), in rats chronically infused with 1 -deamino-8-D-arginine-VP (dDAVP), or in rats subjected to bilateral adrenalectomy. All these experimental situations are known to have an impact on VP synthesis in different ways: the magnocellular VP neurons of the supraoptic (SON) and paraventricular (PVN) nuclei are mainly involved in the modifications of hydric balance (2) whereas adrenalectomy stimulates a subset of parv...

Increased Colocalization of Corticotropin‐Releasing Factor and Arginine Vasopressin in Paraventricular Neurones of the Hypothalamus in Lactating Rats: Evidence from Immunotargeted Lesions and Immunohistochemistry

“…These results strongly suggest that increased parvocellular colocalization of AVP and CRF in the lactating female favours targeting and functional destruction of CRF neurones by increasing the overall synthetic activity of these neurones (at least with respect to AVP). Since the efficiency of toxin penetration and lesion depends on the state of synthetic activity of neuropeptidergic neurones (36), by expressing increased AVP, parvocellular CRF neurones become more sensitive to the effects of the lesions. Indeed, we observed a greater reduction in size of the labelled area and intensity of labelling for both CRF and AVP lesions in lactating females (CRF: P < 0.01 for both surface and grains).…”