Ultrasonic vocalizations of preweanling rats: involvement of both alpha(2)-adrenoceptor and kappa-opioid receptor systems.
Stimulation of alpha(2)-adrenoceptors and kappa-opioid receptors increases the ultrasonic vocalizations of preweanling rats. The purpose of the present study was to determine whether alpha(2)-adrenoceptors and kappa-opioid receptors modulate ultrasonic vocalization production via a common mechanism. To that end, 11-day-old rats were injected with the alpha(2)-adrenoceptor antagonist yohimbine (0, 0.5, or 1.0 mg/kg, i.p.) or the kappa-opioid receptor antagonist nor-binaltorphimine (0, 5, or 10 mg/kg, i.p.). After 15 min, the same rats were injected with saline, the alpha(2)-adrenoceptor agonist clonidine (0.25 mg/kg, i.p.), or the kappa-opioid receptor agonist trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate (U-50,488; 2.5 mg/kg, i.p.). Results showed that both clonidine and U-50,488 increased the ultrasonic vocalizations of preweanling rats. Not surprisingly, clonidine-induced ultrasonic vocalizations were blocked by yohimbine, while U-50,488-induced vocalizations were blocked by nor-binaltorphimine. Importantly, yohimbine also attenuated the vocalizations produced by U-50,488, whereas nor-binaltorphimine did not alter clonidine-induced ultrasonic vocalizations. Thus, it appears that alpha(2)-adrenoceptor and kappa-opioid receptor stimulation increases ultrasonic vocalization production via a common mechanism. It is likely that the kappa-opioid receptors responsible for modulating ultrasonic vocalizations are located "upstream" from the alpha(2)-adrenoceptors.
Nazarian
A
A
Department of Psychology, California State University, San Bernardino 92407, USA.
Krall
C M
CM
Osburn
J R
JR
McDougall
S A
SA
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D003000:Clonidine / Q000494:pharmacology*; D005260:Female; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects* / Q000502:physiology; D017473:Receptors, Opioid, kappa / Q000187:drug effects* / Q000502:physiology; D014828:Vocalization, Animal / Q000187:drug effects* / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018712:Analgesics, Non-Narcotic; D009292:Narcotic Antagonists; D018341:Receptors, Adrenergic, alpha-2; D017473:Receptors, Opioid, kappa; D015016:Yohimbine; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D003000:Clonidine