Neural Mechanism of Mammalian Vocalization

comment on Dr. Brudzynksi's presentation

Dr Brudzynski,
We have found that a cholinergic receptor antagonist, benactyzine HCl, reliably enhances production of alarm calls by adult squirrel monkeys. In our initial paper (1),
we presented dose-response curves, and gave examples of the calls to illustrate that calls produced under drug treatment were indistinguishable from those produced under vehicle treatment--only call rate changed. In that paper, we also showed that physostigmine, but not neostigmine, blocked the benactyzine effect, suggesting that benactyzine was acting centrally. A second paper (2) showed that pretreatment for several days with 1 mg/kg diazepam followed by a single injection of benactyzine or several benzodiazepine receptor ligands enhanced the response over benactyzine preceded by saline injections. Subsequent papers showed that a drug that enhances isolation calls (yohimbine) failed to have any effect on alarm calls (3), and that benactyzine, at a dose that enhanced alarm calling, had no effect on isolation call production (4). That same paper (4) also showed that females had a stronger response to a standard alarm-eliciting stimulus, both in the presence and absence of benactyzine. A final paper in the series (5) provided more details regarding dose-response results for males and females, and also showed that benactyzine actually reduced isolation call rate at certain doses, more so in males than in females.
Thus, these studies also implicate a cholinergic mechanism in vocal alarm-in this case, in a nonhuman primate--and suggest a modulatory role for the benzodiazepine receptor.

References:
1. Glowa, JR, Newman, JD. 1986. Benactyzine increases alarm call rates in the squirrel monkey. Psychopharmacology 90: 457-460.
2. Glowa, JR, Bergman J, Insel T, Newman JD. 1988. Drug effects on primate alarm vocalizations. In: The Physiological Control of Mammalian Vocalization, J. D. Newman, editor, pp. 343-366, Plenum Press, New York.
3. Newman, JD. 1988. Ethopharmacology of vocal behavior in primates. In: Primate Vocal Communication, D. Todt, P. Goedeking, D. Symmes, editors, pp. 145-153, Springer-Verlag, Berlin.
4. Crepeau LJ, Newman JD. 1991. Gender differences in reactivity of adult squirrel monkeys to short-term environmental challenges. Neurosci. Biobehav. Rev. 15: 469-471.
5. Newman JD, Farley, MJ. 1995. An ethologically based, stimulus and gender-sensitive nonhuman primate model for anxiety. Prog. Neuro-Psychopharmacol. & Biol. Psychiat. 19: 677-685.

Thank you for organizing the symposium. I already see the benefit of being able to provide immediate feedback to a symposium presentation through this mechanism.

Mon Dec 7