Clinical use of naloxone/calcium association in the meconium impaction and prevention of stress-related disorders of weaning in foals

摘要

First 24 hours of life and weaning of foals are two critical and stressful conditions in which gastrointestinal and skeletal pathologies, can arise. Neonatal meconium impaction show characteristic symptoms: restlessness, reduced frequency of nursing,nervous walking-box with elevated tail, swishing of the tail, colic pain, rolling, dorsal recumbency, straining with kyphosis, (Traub-Dargatz, 1992; Bucca, 1997; Bernard, 2002, Lacalandra et al, 2001). Retained meconium, if not promptly diagnosed and treated, can induce serious consequences and death. For resolution, saline and paraffin enema was indicated or enterectomy if the impaction is located in the large colon. This pathology is principally linked to lack of colostrum assumption, but the functional cause is the reduced intestinal motility (faecal stasis), which is related to a reduced internal concentration of calcium ions in the smooth muscular cells. These cells are in connection with neuronal circuits in the gut wall, and those of non-neuronal "pacemaker" cells (Hirst, 1999). Binding studies have documented the presence of opioid receptors on nerve and smooth muscle in the gastrointestinal tract (Kummerle et al., 1992; Bagnol et al., 1995). The high level of endogenous opioids is capable ofinteracting with the balance between intracellular and extracellular calcium levels. Mainly in the periparturient period calcium turnover can be negatively influenced by the high level of bate-endorfin in mother circulating blood and consequently at foetal/newborn circulation (Minoia and Sciorsci, 1994). Naloxone (antagonist of Endogenous Opioid Peptides) in Calcium Gluconate solution, removes endorphins from the specific cellular membrane receptors, re-establishing the membrane potential and functionality of smooth muscular cells (Sciorsci et al., 2000a). In the colic syndrome of adult horses this pharmacological association showed its therapeutic efficacy (Sciorsci et al., 2000b).