Food intake and rumen motility in dwarf goats. Effects of atipamezole on the inhibitory effects induced by detomidine, medetomidine and romifidine

Abstract

The effects of some alpha 2-adrenoceptor agonists and of the alpha 2-adrenoceptor antagonist atipamezole on food intake and ruminal contractions were studied in dwarf goats. Detomidine, 0.2 microgram/kg per min for 10 min, failed to modify food intake during either the first or second observation period (0-30 min and 180-210 min after drug infusion, respectively). Given at a higher dose rate (0.4 microgram/kg per min for 10 min), the drug inhibited food consumption during the first observation period, but stimulated food intake during the second period. A similar pattern was observed after IV infusion with medetomidine (0.2 microgram/kg per min for 10 min), romifidine (0.4 microgram/kg per min for 10 min) or xylazine (1 microgram/kg per min for 10 min). The alpha 2-antagonist atipamezole (2 micrograms/kg per min for 10 min) failed to modify food intake during either the first or second observation period. After treatment with atipamezole, the effects of alpha 2-agonists on feeding behaviour were completely antagonized. The alpha 2-agonists administered at similar dose rates to those used in the food intake experiments induced bradycardia, decreases in body temperature and inhibition of ruminal contractions. The inhibition of ruminal contractions induced by romifidine was partly antagonized by atipamezole pre-treatment. These findings demonstrate that the alpha 2-agonist-induced changes in ruminal contractions do not simply cause changes in feeding behaviour. The drop in body temperature induced by alpha 2-agonists was prevented by atipamezole pre-treatment, whereas the induced bradycardia was not modified by this alpha 2-antagonist.

Transmitter-equipped darts in a protocol for chemically immobilizing free-ranging red deer (Cervus elaphus) in Central Italy

“…The alpha-2 adrenergic drugs promote sympathetic nervous system depression and a consequent increase in the parasympa- thetic activity with many physiologic effects and ruminal-reticular atony (van Miert, 1994;DeRossi et al, 2005). This aspect, recumbence and a mix of seasonal foods may explain the described ruminal meteorism.…”

“…A critical aspect of chemical immobilization may cause hypoventilation and hypoxemia resulting from depression of central respiratory centres (Caulkett, 1997;Caulkett et al, 2000;Janovsky et al, 2000;Murray et al, 2000;Matt, 2001;Read et al, 2001). In addition the animals may assume positions that prevent complete pulmonary ventilation (Doherty et al, 1986;Doherty et al, 1987) and/or show quick ruminal meteorism (van Miert, 1994;DeRossi et al, 2005) deriving from ruminal atony and/or incorrect recumbence. Hence, it is of the utmost importance to consider that hypoxemia can result in a predisposition to tissue hypoxia, myocardial ischemia, and organ failure similar to capture myopathy (Spreaker, 1993).…”

Pharmacological and pathophysiological modulation of food intake and forestomach motility in small ruminants

“…Furthermore, the α 2 ‐agonists xylazine and detomidine increased feeding when injected systemically ( Majeed et al ., 1991 ). These orexigenic effects could not be prevented by the α 1 ‐antagonist prazosin ( van Miert et al ., 1994b ; Currie, 1996). Interestingly, the impact of peripherally and centrally administered clonidine on food intake appears to be biphasic, such that low doses stimulate appetite, whereas higher doses tend to suppress feeding behaviour ( Currie, 1996).…”

“…In small ruminants, the specific neurotransmitters for which there is evidence for a physiological function in feed intake regulation include the orexigenic agents noradrenaline (via α 1 ‐receptors), glutamate ( Wandji et al ., 1989 ) gamma‐aminobutyric acid (GABA)‐benzodiazepines ( de Jong, 1987; van Miert et al ., 1989 ), opioid agonist peptides ( Baile & McLaughlin, 1987; van Miert et al ., 1989 ), pancreatic polypeptides (neuropeptide‐Y; Miner et al ., 1989a,b, 1990a), and possibly melanocyte‐concentrating hormone ( Qu et al ., 1996 ); the anorectic neurotransmitters and peptides include cholecystokinin ( Della‐Fera & Baile, 1980; Baile et al ., 1983 ; Rose et al ., 1996 ), serotonin ( Blundell, 1992; Kaya et al ., 1992 ), α 2 ‐adrenoceptor agonists ( Miner et al ., 1990b ; van Miert & van Duin, 1991; van Miert et al ., 1994b ; Currie, 1996), and possibly urocortin‐corticotropin releasing factor ( Spina et al ., 1996 ), bombesin‐like peptides ( Morley, 1987; Ladenheim et al ., 1996 ) and glucagon‐like peptide 1 ( Turton et al ., 1996 ). In contrast to rodents, there is no evidence in ruminants for a central role of dopamine in feed intake regulation ( Kaya et al ., 1994 ).…”

“…The procedures for recording food intake, ruminal contractions, heart rate and rectal temperature were the same as those described previously ( Kaya et al ., 1994 ; van Miert et al ., 1994b ).…”